Contents:

Module / Lessons Page

Module 1 Principles of Water Resources Engineering 4
Lesson 1 Surface and Ground Water Resources
Lesson 2 Concepts for Planning Water Resources Development 39
Lesson 3 National Policy For Water Resources Development 53
Lesson 4 Planning and Assessment of Data for Project Formulation 70
Module 2 The Science of Surface and Ground Water 98
Lesson 1 Precipitation And Evapotranspiration
Lesson 2 Runoff and Infiltration 116
Lesson 3 Rainfall Runoff Relationships 129
Lesson 4 Design Flood Estimation 150
Lesson 5 Subsurface Movement of Water 172
Lesson 6 Principles of Ground Water Flow 191
Lesson 7 Well Hydraulics 216
Lesson 8 Flow Dynamics in Open Channels and Rivers 238
Lesson 9 Geomorphology of Rivers 280
Lesson 10 Sediment Dynamics in Alluvial Rivers and Channels 305
Module 3 Irrigation Engineering Principles 325
Lesson 1 India’s Irrigation Needs and Strategies for Development
Lesson 2 Soil Water Plant Relationships 354
Lesson 3 Estimating Irrigation Demand 372
Lesson 4 Types of Irrigation Schemes and Methods of Field Water 394
Application
Lesson 5 Traditional Water Systems and Minor Irrigation Schemes 421
Lesson 6 Canal Systems for Major and Medium Irrigation Schemes 441
Lesson 7 Design of Irrigation Canals 455
Lesson 8 Conveyance Structures for Canal Flows 483
Lesson 9 Regulating Structures for Canal Flows 505
Lesson 10 Distribution and Measurement Structures for Canal Flows 532
Module 4 Hydraulic Structures for Flow Diversion and Storage 556
Lesson 1 Structures for Flow Diversion - Investigation Planning and
Layout
Lesson 2 Design of the Main Diversion Structure of a Barrage 587
Lesson 3 Design of Barrage Appurtenant Structures and Rules for 621
Barrage Operation
Lesson 4 Structures for Water Storage - Investigation, Planning and 647
Layout
Lesson 5 Planning Of Water Storage Reservoirs 692
Lesson 6 Design and Construction of Concrete Gravity Dams 736
Lesson 7 Design and Construction of Concrete Gravity Dams 805
Lesson 8 Spillways and Energy Dissipators 870
Lesson 9 Reservoir Outlet Works 945
Lesson 10 Gates and Valves for Flow Control 970
Module 5 Hydropower Engineering 1018
Lesson 1 Principles of Hydropower Engineering
Lesson 2 Hydropower Water Conveyance System 1052
Lesson 3 Hydropower Eqiupment And Generation Stations 1088
Module 6 Management of Water Resources 1117
Lesson 1 River Training And Riverbank Protection Works
Lesson 2 Drought And Flood Management 1152
Lesson 3 Remote Sensing And GIS For Water Resource Management 1180
 Module
1
Principles of Water
Resources Engineering
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 Lesson
1
Surface and Ground
Water Resources
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Instructional Objectives
After completion of this lesson, the student shall know about
1. Hydrologic cycle and its components
2. Distribution of earth’s water resources
3. Distribution of fresh water on earth
4. Rainfall distribution in India
5. Major river basins of India
6. Land and water resources of India; water development potential
7. Need for development of water resources

1.1.0 Introduction
Water in our planet is available in the atmosphere, the oceans, on land and
within the soil and fractured rock of the earth’s crust Water molecules from one
location to another are driven by the solar energy. Moisture circulates from the
earth into the atmosphere through evaporation and then back into the earth as
precipitation. In going through this process, called the Hydrologic Cycle (Figure
1), water is conserved – that is, it is neither created nor destroyed.

Figure 1. Hydrologic cycle

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It would perhaps be interesting to note that the knowledge of the hydrologic cycle
was known at least by about 1000 BC by the people of the Indian Subcontinent.
This is reflected by the fact that one verse of Chhandogya Upanishad (the
Philosophical reflections of the Vedas) points to the following:

“The rivers… all discharge their waters into the sea. They lead from sea to sea,
the clouds raise them to the sky as vapour and release them in the form of
rain…”

The earth’s total water content in the hydrologic cycle is not equally distributed
(Figure 2).

Figure 2. Total global water content

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The oceans are the largest reservoirs of water, but since it is saline it is not
readily usable for requirements of human survival. The freshwater content is just
a fraction of the total water available (Figure 3).

Figure 3. Global fresh water distribution

Again, the fresh water distribution is highly uneven, with most of the water locked
in frozen polar ice caps.

The hydrologic cycle consists of four key components

1. Precipitation
2. Runoff
3. Storage
4. Evapotranspiration

These are described in the next sections.

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1.1.1 Precipitation
Precipitation occurs when atmospheric moisture becomes too great to remain
suspended in clouds. It denotes all forms of water that reach the earth from the
atmosphere, the usual forms being rainfall, snowfall, hail, frost and dew. Once it
reaches the earth’s surface, precipitation can become surface water runoff,
surface water storage, glacial ice, water for plants, groundwater, or may
evaporate and return immediately to the atmosphere. Ocean evaporation is the
greatest source (about 90%) of precipitation.

Rainfall is the predominant form of precipitation and its distribution over the world
and within a country. The former is shown in Figure 4, which is taken from the
site http://cics.umd.edu/~yin/GPCP/main.html of the Global Precipitation
Climatology Project (GPCP) is an element of the Global Energy and Water Cycle
Experiment (GEWEX) of the World Climate Research program (WCRP).

Figure 4. A typical distribution of global precipitation (Courtesy: Global

Precipitation Climatology Project)

The distribution of precipitation for our country as recorded by the India

Meteorological Department (IMD) is presented in the web-site of IMD
http://www.imd.ernet.in/section/climate/. One typical distribution is shown in
Figure 5 and it may be observed that rainfall is substantially non-uniform, both in
space and over time.

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 Figure 5. A typical distribution of rainfall within India for a particular week
(Courtsey: India Meteorological Department)

India has a typical monsoon climate. At this time, the surface winds undergo a
complete reversal from January to July, and cause two types of monsoon. In
winter dry and cold air from land in the northern latitudes flows southwest
(northeast monsoon), while in summer warm and humid air originates over the
ocean and flows in the opposite direction (southwest monsoon), accounting for
some 70 to 95 percent of the annual rainfall. The average annual rainfall is
estimated as 1170 mm over the country, but varies significantly from place to
place. In the northwest desert of Rajasthan, the average annual rainfall is lower
than 150 mm/year. In the broad belt extending from Madhya Pradesh up to
Tamil Nadu, through Maharastra, parts of Andhra Pradesh and Karnataka, the
average annual rainfall is generally lower than 500 mm/year. At the other
extreme, more than 10000 mm of rainfall occurs in some portion of the Khasi
Hills in the northeast of the country in a short period of four months. In other
parts of the northeast (Assam, Arunachal Pradesh, Mizoram, etc.,) west coast

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and in sub-Himalayan West Bengal the average annual rainfall is about 2500
mm.

Except in the northwest of India, inter annual variability of rainfall in relatively

low. The main areas affected by severe droughts are Rajasthan, Gujarat (Kutch
and Saurashtra).

The year can be divided into four seasons:

• The winter or northeast monsoon season from January to February.
• The hot season from March to May.
• The summer or south west monsoon from June to September.
• The post – monsoon season from October to December.

The monsoon winds advance over the country either from the Arabian Sea or
from the Bay of Bengal. In India, the south-west monsoon is the principal rainy
season, which contributes over 75% of the annual rainfall received over a major
portion of the country. The normal dates of onset (Figure 6) and withdrawal
(Figure 7) of monsoon rains provide a rough estimate of the duration of monsoon
rains at any region.

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Figure 6. Normal onset dates for Monsoon (Courtsey: India Meteorological
Department)

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Figure 7. Normal withdrawal dates for Monsoon (Courtsey: India Meteorological
Department)

1.1.2 Runoff
Runoff is the water that flows across the land surface after a storm event. As
rain falls over land, part of that gets infiltrated the surface as overland flow. As
the flow bears down, it notches out rills and gullies which combine to form
channels. These combine further to form streams and rivers.

The geographical area which contributes to the flow of a river is called a river or a
watershed. The following are the major river basins of our country, and the

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corresponding figures, as obtained from the web-site of the Ministry of Water
Resources, Government of India (http://www.wrmin.nic.in) is mentioned
alongside each.

1. Indus (Figure 8)
2. Ganges (Figure 9)
3. Brahmaputra (Figure 10)
4. Krishna (Figure 11)
5. Godavari (Figure 12)
6. Mahanandi (Figure 13)
7. Sabarmati (Figure 14)
8. Tapi (Figure 15)
9. Brahmani-Baitarani (Figure 16)
10. Narmada (Figure 17)
11. Pennar (Figure 18)
12. Mahi (Figure 19)

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Some statistical information about the surface water resources of India, grouped
by major river basin units, have been summarised as under. The inflow has been
collected from the inistry of Water Resources, Government of India web-site.

River basin unit Location Draining Catchment Average Utilizable

into area km2 annual surface
runoff water
(km3) (km3)
1 Ganges- Northeast Bangladesh
Brahmaputra-
Meghna 861 452 525.02* 250.0
-Ganges (1) 537.24* 24.0
- 193 48.36 -
Brahmaputra(2) 413(1)
-Barak(3) 41 113.53 24.3
2 Southwest Arabian 723(1)
West flowing coast sea
river from Tadri 56 177 110.54 76.3
3 to Kanyakumari 87.41 11.9
4 Central Bay of
Godavari Central- Bengal 312 812 78.12 58.0
5 West flowing West Arabian 55 940 73.31* 46.0
6 rivers from Tapi coast sea 66.88* 50.0
7 to Tadri Central 258 948 45.64 34.5
8 Krishan Northwest Bay of 321 31.00* -
9 Indus Central- Bengal 289(1)
Mahanadi east Pakistan 141 589 28.48 18.3
10 Namada(5) Central- Bay of 98 796 22.52 13.1
11 Minor rivers of west Bengal 36
the northeast Extreme Arabian 302(1)
Brahmani- northeast sea 21.36 19.0
12 Baitarani Northeast Myanmar 51 822 16.46 16.7
13 East flowing Central- and 86 643
rivers between east coast Bangladesh
Mahanadi & Bay of 15.10 15.0
14 Pennar Bengal 81 155
South Bay of 100 139 14.88 14.5
15 Cauvery(4) Southeast Bengal 12.37 6.8
16 East flowing coast 11.02 3.1
17 rivers between 321 851 6.32 6.9
18 Kanyakumari Bay of 3.81 1.9
19 and Pennar Northwest Bengal 65 145 negligible -
20 coast Bay of 29 196
West flowing Central- Bengal 34 842
rivers of Kutsh west 55 213
and Saurashtra Northeast 21 674

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 Tapi Northwest Arabian -
Subernarekha Southeast sea
Mahi Northwest
Pennar northwest Arabian
Sabarmati sea
Rajasthan and Bay of
inland basin Bengal
Arabian
sea
Bay of
Bengal
Arabian
sea
-

Total 3 227 121 1 869.35 690.3

* Earlier estimates reproduced from Central Water Commission (1988).

Notes:

(1) Areas given are those in India territory.

(2) The potential indicated for the Brahmaputra is the average annual flow at
Jogighopa situated 85 km upstream of the India-Bangladesh border. The
area drained by the tributaries such as the Champamati, Gaurang, Sankosh,
Torsa, Jaldhaka and Tista joining the Brahmaputra downstream of Jogighopa
is not accounted for in this assessment.
(3) The potential for the Barak and others was determined on the basis of the
average annual flow at Badarpurghat (catchment area: 25 070 km2) given in
a Brahmaputra Board report on the Barak sub-basin.
(4) The assessment for Cauvery was made by the Cauvery Fact Finding
Committee in 1972 based on 38 years’ flow data at Lower Anicut on
Coleroon. An area of nearly 8 000 km2 in the delta is not accounted for in
this assessment.
(5) The potential of the Narmada basin was determined on the basis of
catchment area proportion from the potential assessed at Garudeshwar
(catchment area: 89 345 km2) as given in the report on Narmada Water
Disputes Tribunal Decision (1978).

1.1.3 Storage
Portion of the precipitation falling on land surface which does not flow out as
runoff gets stored as either as surface water bodies like Lakes, Reservoirs and
Wetlands or as sub-surface water body, usually called Ground water.

Ground water storage is the water infiltrating through the soil cover of a land
surface and traveling further to reach the huge body of water underground. As

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mentioned earlier, the amount of ground water storage is much greater than that
of lakes and rivers. However, it is not possible to extract the entire groundwater
by practicable means. It is interesting to note that the groundwater also is in a
state of continuous movement – flowing from regions of higher potential to lower.
The rate of movement, however, is exceptionally small compared to the surface
water movement.

The following definitions may be useful:

Lakes: Large, naturally occurring inland body of water

Reservoirs: Artificial or natural inland body of water used to store water to meet
various demands.
Wet Lands: Natural or artificial areas of shallow water or saturated soils that
contain or could support water–loving plants.

1.1.4 Evapotranspiration
Evapotranspiration is actually the combination of two terms – evaporation and
transpiration. The first of these, that is, evaporation is the process of liquid
converting into vapour, through wind action and solar radiation and returning to
the atmosphere. Evaporation is the cause of loss of water from open bodies of
water, such as lakes, rivers, the oceans and the land surface. It is interesting to
note that ocean evaporation provides approximately 90 percent of the earth’s
precipitation. However, living near an ocean does not necessarily imply more
rainfall as can be noted from the great difference in the amount of rain received
between the east and west coasts of India.

Transpiration is the process by which water molecules leaves the body of a living
plant and escapes to the atmosphere. The water is drawn up by the plant root
system and part of that is lost through the tissues of plant leaf (through the
stomata). In areas of abundant rainfall, transpiration is fairly constant with
variations occurring primarily in the length of each plants growing season.
However, transpiration in dry areas varies greatly with the root depth.

Evapotranspiration, therefore, includes all evaporation from water and land

surfaces, as well as transpiration from plants.

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1.1.5 Water resources potential
1.1.5.1 Surface water potential:

The average annual surface water flows in India has been estimated as 1869
cubic km. This is the utilizable surface water potential in India. But the amount
of water that can be actually put to beneficial use is much less due to severe
limitations posed by Physiography, topography, inter-state issues and the
present state of technology to harness water resources economically. The recent
estimates made by the Central Water Commission, indicate that the water
resources is utilizable through construction of structures is about 690 cubic km
(about 36% of the total). One reason for this vast difference is that not only does
the whole rainfall occur in about four months a year but the spatial and temporal
distribution of rainfall is too uneven due to which the annual average has very
little significance for all practical purposes.

Monsoon rain is the main source of fresh water with 76% of the rainfall occurring
between June and September under the influence of the southwest monsoon.
The average annual precipitation in volumetric terms is 4000 cubic km. The
average annual surface flow out of this is 1869 cubic km, the rest being lost in
infiltration and evaporation.

1.1.5.2 Ground water potential:

The potential of dynamic or rechargeable ground water resources of our country

has been estimated by the Central Ground Water Board to be about 432 cubic
km.

Ground water recharge is principally governed by the intensity of rainfall as also

the soil and aquifer conditions. This is a dynamic resource and is replenished
every year from natural precipitation, seepage from surface water bodies and
conveyance systems return flow from irrigation water, etc.

The highlighted terms are defined or explained as under:

Utilizable surface water potential: This is the amount of water that can be
purpose fully used, without any wastage to the sea, if water storage and
conveyance structures like dams, barrages, canals, etc. are suitably built at
requisite sites.

Central Water Commission: Central Water Commission is an attached office of

Ministry of Water Resources with Head Quarters at New Delhi. It is a premier
technical organization in the country in the field of water resources since 1945.

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The commission is charged with the general responsibility of initiating,
coordinating and furthering, in consultation with the State Governments
concerned, schemes for control, conservation and utilization of water resources
throughout the country, for purpose of flood control, irrigation, navigation,
drinking water supply and water power development.

Central Ground Water Board: It is responsible for carrying out nation-wide

surveys and assessment of groundwater resources and guiding the states
appropriately in scientific and technical matters relating to groundwater. The
Central Ground Water Board has generated valuable scientific and technical data
through regional hydro geological surveys, groundwater exploration, resource
and water quality monitoring and research and development. It assists the States
in developing broad policy guidelines for development and management of
groundwater resources including their conservation, augmentation and protection
from pollution, regulation of extraction and conjunctive use of surface water and
ground water resources. The Central Ground Water Board organizes Mass
Awareness Programmes to create awareness on various aspects of groundwater
investigation, exploration, development and management.

Ground water recharge: Some of the water that precipitates, flows on ground
surface or seeps through soil first, then flows laterally and some continues to
percolate deeper into the soil. This body of water will eventually reach a
saturated zone and replenish or recharge groundwater supply. In other words,
the recuperation of groundwater is called the groundwater recharge which is
done to increase the groundwater table elevation. This can be done by many
artificial techniques, say, by constructing a detention dam called a water
spreading dam or a dike, to store the flood waters and allow for subsequent
seepage of water into the soil, so as to increase the groundwater table. It can
also be done by the method of rainwater harvesting in small scale, even at
individual houses. The all India figure for groundwater recharge volume is 418.5
cubic km and the per capita annual volume of groundwater recharge is 412.9
cubic m per person.

1.1.6 Land and water resources of India

The two main sources of water in India are rainfall and the snowmelt of glaciers
in the Himalayas. Although reliable data on snow cover in India are not
available, it is estimated that some 5000 glaciers cover about 43000 km2 in the
Himalayas with a total volume of locked water estimated at 3870 km3.
considering that about 10000 km2 of the Himalayan glacier is located within
India, the total water yield from snowmelt contributing to the river runoff in India
may be of the order of 200 km3/year. Although snow and glaciers are poor
producers of fresh water, they are good distributors as they yield at the time of
need, in the hot season.

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The total surface flow, including regenerating flow from ground water and the
flow from neighbouring countries is estimated at 1869 km3/year, of which only
690 km3 are considered as utilizable in view of the constraints of the present
technology for water storage and inter – state issues. A significant part (647.2
km3/year) of these estimated water resources comes from neighbouring
countries; 210.2 km3/year from Nepal, 347 km3/year from China and 90
km3/year from Bhutan. An important part of the surface water resources leaves
the country before it reaches the sea: 20 km3/year to Myanmar, 181.37 km3/year
to Pakistan and 1105.6 km3/year to Bangladesh (“Irrigation in Aisa in Figures”,
Food and Agricultural Organisation of the United Nations, Rome, 1999;
http://www.fao.org/ag/agL/public.stm). For further information, one may also
check the web-site “Earth Trends” http://elearthtrends.wri.org.

The land and water resources of India may be summarized as follows.

Geographical area 329 million
hectare
Natural runoff (Surface water and ground water) 1869 cubic
km/year
Estimated utilizable surface water potential 690 cubic
km/year
Ground water resources 432 cubic
km/year
Available ground water resource for irrigation 361 cubic
km/year
Net utilizable ground water resource for irrigation 325 cubic
km/year

1.1.7 International indicators for comparing water resources

potential
Some of the definitions used to quantify and compare water resource potential
internationally are as follows:

1. Internal Renewable Water Resources (IRWR): Internal Renewable

Water Resources are the surface water produced internally, i.e., within a
country. It is that part of the water resources generated from endogenous
precipitation. It is the sum of the surface runoff and groundwater recharge
occurring inside the countries' borders. Care is taken strictly to avoid
double counting of their common part. The IRWR figures are the only
water resources figures that can be added up for regional assessment and
they are being used for this purpose.

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2. Surface water produced internally: Total surface water produced
internally includes the average annual flow of rivers generated from
endogenous precipitation (precipitation occurring within a country's
borders). It is the amount of water produced within the boundary of a
country, due to precipitation. Natural incoming flow originating from
outside a country’s borders is not included in the total.

3. Groundwater recharge: The recuperation of groundwater is called the

groundwater recharge. This is requisite to increase the groundwater table
elevation. This can be done by many artificial techniques, say, by
constructing a detention dam called a water spreading dam or a dike, to
store the flood waters and allow for subsequent seepage of water into the
soil, so as to increase the groundwater table. It can also be done by the
method of rainwater harvesting in small scale, even at individual houses.
The groundwater recharge volume is 418.5 cubic km and the per capita
annual volume of groundwater recharge is 412.9 cubic m per person.

4. Overlap: It is the amount of water quantity, coinciding between the

surface water produced internally and the ground water produced
internally within a country, in the calculation of the Total Internal
Renewable Water Resources of the country. Hence, Overlap = Total
IRWR- (Surface water produced internally + ground water produced
internally). The overlap for Indian water resources is 380 cubic km.

5. Total internal Renewable Water Resources: The Total Internal

Renewable Water Resources are the sum of IRWR and incoming flow
originating outside the countries' borders. The total renewable water
resources of India are 1260.5 cubic km.

6. Per capita Internal Renewable Water Resources: The Per capita annual
average of Internal Renewable Water Resources is the amount of average
IRWR, per capita, per annum. For India, the Per capita Internal
Renewable Water Resources are 1243.6 cubic m.

7. Net renewable water resources: The total natural renewable water

resources of India are estimated at 1907.8 cubic km per annum, whereas
the total actual renewable water resources of India are 1896.7 cubic km.

8. Per capita natural water resources: The present per capita availability of
natural water, per annum is 1820 cubic m, which is likely to fall to 1341
cubic m, by 2025.

9. Annual water withdrawal: The total amount of water withdrawn from the
water resources of the country is termed the annual water withdrawal. In
India, it amounts 500000 to million cubic m.

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 10. Per capita annual water withdrawal: It is the amount of water withdrawn
from the water resources of the country, for various purposes. The per
capita annual total water withdrawal in India is 592 cubic m per person.

The above definitions have been provided by courtesy of the following web-site:
http://earthtrends.wri.org/text/theme2vars.htm.

1.1.8 Development of water resources

Due to its multiple benefits and the problems created by its excesses, shortages
and quality deterioration, water as a resource requires special attention.
Requirement of technological/engineering intervention for development of water
resources to meet the varied requirements of man or the human demand for
water, which are also unevenly distributed, is hence essential.

The development of water resources, though a necessity, is now pertinent to be

made sustainable. The concept of sustainable development implies that
development meets the needs of the present life, without compromising on the
ability of the future generation to meet their own needs. This is all the more
important for a resource like water. Sustainable development would ensure
minimum adverse impacts on the quality of air, water and terrestrial environment.
The long term impacts of global climatic change on various components of
hydrologic cycle are also important.

India has sizeable resources of water and a large cultivable land but also a large
and growing population to feed. Erratic distribution of rainfall in time and space
leads to conditions of floods and droughts which may sometimes occur in the
same region in the same year. India has about 16% of the world population as
compared to only 4% of the average annual runoff in the rivers.

With the present population of more than 1000 million, the per capita water
availability comes to about 1170 m3 per person per year. Here, the average does
not reflect the large disparities from region to region in different parts of the
country. Against this background, the problems relating to water resources
development and management have been receiving critical attention of the
Government of India. The country has prepared and adopted a comprehensive
National Water Policy in the year 1987, revised in 2002 with a view to have a
systematic and scientific development of it water resources. This has been dealt
with in Lesson 1.3, “Policies for water resources development”.

Some of the salient features of the National Water Policy (2002) are as follows:
• Since the distribution of water is spatially uneven, for water scarce areas,
local technologies like rain water harvesting in the domestic or community
level has to be implemented.

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 • Technology for/Artificial recharge of water has also to be bettered.
• Desalination methods may be considered for water supply to coastal
towns.

1.1.9 Present water utilization in India

Irrigation constitutes the main use of water and is thus focal issue in water
resources development. As of now, irrigation use is 84 percent of total water
use. This is much higher than the world’s average, which is about 65 percent. For
advanced nations, the figure is much lower. For example, the irrigation use of
water in USA is around 33 percent. In India, therefore, the remaining 16 percent
of the total water use accounts for Rural domestic and livestock use, Municipal
domestic and public use, Thermal-electric power plants and other industrial uses.
The term irrigation is defined as the artificial method of applying water to crops.
Irrigation increases crop yield and the amount of land that can be productively
farmed, stabilizes productivity, facilitates a greater diversity of crops, increases
farm income and employment, helps alleviate poverty and contributes to regional
development.

1.1.10 Need for future development of water resources

The population of India has been estimated to stabilize by about 2050 A.D. By
that time, the present population of about 1000 million has been projected to be
about 1800 million (considering the low, medium and high estimates of 1349
million 1640 million and 1980 million respectively). The present food grain
availability of around 525 grams per capita per day is also presumed to rise to
about 650 grams, considering better socio-economic lifestyle (which is much less
than the present figures of 980 grams and 2850 grams per capita per day for
China and U.S.A., respectively). Thus, the annual food grain requirement for
India is estimated to be about 430 MT. Since the present food grain production is
just sufficient for the present population, it is imperative that additional area
needs to be brought under cultivation. This has been estimated to be 130 Mha
for food crop alone and 160 Mha for all crops to meet the demands of the country
by 2050 A.D.

Along with the inevitable need to raise food production, substantial thrust should
be directed towards water requirement for domestic use. The national agenda for
governance aims to ensure provision of potable water supply to every individual
in about five years time. The National Water Policy (2002) has accorded topmost
water allocation priority to drinking water. Hence, a lot of technological
intervention has to be made in order to implement the decision. But this does not

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mean that unlimited funds would be allocated for the drinking water sector. Only
20% of urban demand is meant for consumptive use . A major concern will
therefore be the treatment of urban domestic effluents.
Major industrial thrust to steer the economy is only a matter of time. By
2050, India expects to be a major industrial power in the world. Industry needs
water fresh or recycled. Processing industries depend on abundance of water. It
is estimated that 64 cubic km of water will be needed by 2050 A.D. to sustain the
industries. Thermal power generation needs water including a small part that is
consumptive. Taking into account the electric power scenario in 2050 A.D.,
energy related requirement (evaporation and consumptive use) is estimated at
150 cubic km.

Note:
Consumptive use: Consumptive use is the amount of water lost in evapo-
transpiration from vegetation and its surrounding land to the atmosphere,
inclusive of the water used by the plants for building their tissues and to carry on
with their metabolic processes. Evapo-transpiration is the total water lost to the
atmosphere from the vegetative cover on the land, along with the water lost from
the surrounding water body or land mass.

1.1.11 Sustainable water utilisation

The quality of water is being increasingly threatened by pollutant load, which is
on the rise as a consequence of rising population, urbanization, industrialization,
increased use of agricultural chemicals, etc. Both the surface and ground water
have gradually increased in contamination level. Technological intervention in the
form of providing sewerage system for all urban conglomerates, low cost
sanitation system for all rural households, water treatment plants for all industries
emanating polluted water, etc. has to be made. Contamination of ground water
due to over-exploitation has also emerged as a serious problem. It is difficult to
restore ground water quality once the aquifer is contaminated. Ground water
contamination occurs due to human interference and also natural factors . To
promote human health, there is urgent need to prevent contamination of ground
water and also promote and develop cost-effective techniques for purifying
contaminated ground water for use in rural areas like solar stills.

In summary, the development of water resources potential should be such that in

doing so there should not be any degradation in the quality or quantity of the
resources available at present. Thus the development should be sustainable for
future.

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References to web-sites:
1. http://cics.umd.edu/~yin/GPCP/main.html
2. http://www.imd.ernet.in/section/climate/
3. http://www.wrmin.nic.in/

Bibliography:
1. Linsley, R K and Franzini, J B (1979) “Water Resources Engineering”,
Third Edition, McGraw Hill, Inc.
2. Mays, L (2001) “Water Resources Engineering”, First Edition, John Wiley
and Sons.

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 Module
1
Principles of Water
Resources Engineering
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 Lesson
2
Concepts for Planning
Water Resources
Development

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Instructional Objectives
On completion of this lesson, the student shall be able to know:
1. Principle of planning for water resource projects
2. Planning for prioritizing water resource projects
3. Concept of basin – wise project development
4. Demand of water within a basin
5. Structural construction for water projects
6. Concept of inter – basin water transfer project
7. Tasks for planning a water resources project

1.2.0 Introduction
Utilisation of available water of a region for use of a community has perhaps
been practiced from the dawn of civilization. In India, since civilization flourished
early, evidences of water utilization has also been found from ancient times. For
example at Dholavira in Gujarat water harvesting and drainage systems have
come to light which might had been constructed somewhere between 300-1500
BC that is at the time of the Indus valley civilization. In fact, the Harappa and
Mohenjodaro excavations have also shown scientific developments of water
utilization and disposal systems. They even developed an efficient system of
irrigation using several large canals. It has also been discovered that the
Harappan civilization made good use of groundwater by digging a large number
of wells. Of other places around the world, the earliest dams to retain water in
large quantities were constructed in Jawa (Jordan) at about 3000 BC and in Wadi
Garawi (Egypt) at about 2660 BC. The Roman engineers had built log water
conveyance systems, many of which can still be seen today, Qanats or
underground canals that tap an alluvial fan on mountain slopes and carry it over
large distances, were one of the most ingenious of ancient hydro-technical
inventions, which originated in Armenia around 1000BC and were found in India
since 300 BC.

Although many such developments had taken place in the field of water
resources in earlier days they were mostly for satisfying drinking water and
irrigation requirements. Modern day projects require a scientific planning
strategy due to:

1. Gradual decrease of per capita available water on this planet and

especially in our country.
2. Water being used for many purposes and the demands vary in time and
space.

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3. Water availability in a region – like county or state or watershed is not
equally distributed.
4. The supply of water may be from rain, surface water bodies and ground
water.

This lesson discusses the options available for planning, development and
management of water resources of a region systematically.

1.2.1 Water resources project planning

The goals of water resources project planning may be by the use of constructed
facilities, or structural measures, or by management and legal techniques that do
not require constructed facilities. The latter are called non-structural measures
and may include rules to limit or control water and land use which complement or
substitute for constructed facilities. A project may consist of one or more
structural or non-structural resources. Water resources planning techniques are
used to determine what measures should be employed to meet water needs and
to take advantage of opportunities for water resources development, and also to
preserve and enhance natural water resources and related land resources.

The scientific and technological development has been conspicuously evident

during the twentieth century in major fields of engineering. But since water
resources have been practiced for many centuries, the development in this field
may not have been as spectacular as, say, for computer sciences. However,
with the rapid development of substantial computational power resulting reduced
computation cost, the planning strategies have seen new directions in the last
century which utilises the best of the computer resources. Further, economic
considerations used to be the guiding constraint for planning a water resources
project. But during the last couple of decades of the twentieth century there has
been a growing awareness for environmental sustainability. And now,
environmental constrains find a significant place in the water resources project
(or for that matter any developmental project) planning besides the usual
economic and social constraints.

1.2.2 Priorities for water resources planning

Water resource projects are constructed to develop or manage the available

water resources for different purposes. According to the National Water Policy
(2002), the water allocation priorities for planning and operation of water
resource systems should broadly be as follows:

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 1. Domestic consumption
This includes water requirements primarily for drinking, cooking, bathing,
washing of clothes and utensils and flushing of toilets.

2. Irrigation
Water required for growing crops in a systematic and scientific manner in
areas even with deficit rainfall.

3. Hydropower
This is the generation of electricity by harnessing the power of flowing
water.

4. Ecology / environment restoration

Water required for maintaining the environmental health of a region.

5. Industries
The industries require water for various purposes and that by thermal
power stations is quite high.

6. Navigation
Navigation possibility in rivers may be enhanced by increasing the flow,
thereby increasing the depth of water required to allow larger vessels to
pass.

7. Other uses
Like entertainment of scenic natural view.

This course on Water Resources Engineering broadly discusses the facilities to

be constructed / augmented to meet the demand for the above uses. Many a
times, one project may serve more than one purpose of the above mentioned
uses.

1.2.3 Basin – wise water resource project development

The total land area that contributes water to a river is called a Watershed, also
called differently as the Catchment, River basin, Drainage Basin, or simply a
Basin. The image of a basin is shown in Figure 1.

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A watershed may also be defined as a geographic area that drains to a common
point, which makes it an attractive planning unit for technical efforts to conserve
soil and maximize the utilization of surface and subsurface water for crop
production. Thus, it is generally considered that water resources development
and management schemes should be planned for a hydrological unit such as a
Drainage Basin as a whole or for a Sub-Basin, multi-sectorially, taking into
account surface and ground water for sustainable use incorporating quantity and
quality aspects as well as environmental considerations.

Let us look into the concept of watershed or basin-wise project development in

some detail. The objective is to meet the demands of water within the Basin with
the available water therein, which could be surface water, in the form of rivers,
lakes, etc. or as groundwater. The source for all these water bodies is the rain
occurring over the Watershed or perhaps the snowmelt of the glacier within it,
and that varies both temporally and spatially.

Further due to the land surface variations the rain falling over land surface tries to
follow the steepest gradient as overland flow and meets the rivers or drains into
lakes and ponds. The time for the overland flows to reach the rivers may be fast
or slow depending on the obstructions and detentions it meet on the way. Part of
the water from either overland flow or from the rivers and lakes penetrates into
the ground and recharge the ground water. Ground water is thus available almost
throughout the watershed, in the underground aquifers. The variation of the water
table is also fairly even, with some rise during rainfall and a gradual fall at other
times. The water in the rivers is mostly available during the rains. When the rain
stops, part of the ground water comes out to recharge the rivers and that results
in the dry season flows in rivers.

Note:

Temporal: That which varies with time

Spatial: That which varies with time

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1.2.4 Tools for water resources planning and management
The policy makers responsible for making comprehensive decisions of water
resources planning for particular units of land, preferably a basin, are faced with
various parameters, some of which are discussed in the following sections.

1.2.4.1 The supply of water

Water available in the unit

This may be divided into three sources
- Rain falling within the region. This may be utilized directly before it
reaches the ground, for example, the roof – top rain water
harvesting schemes in water scarce areas.

- Surface water bodies. These static (lakes and ponds) and flowing
(streams and rivers), water bodies may be utilized for satisfying the
demand of the unit, for example by constructing dams across
rivers.

- Ground water reservoirs. The water stored in soil and pores of

fractured bed rock may be extracted to meet the demand, for
example wells or tube – wells.

Water transferred in and out of the unit

If the planning is for a watershed or basin, then generally the water available
within the basin is to be used unless there is inter basin water transfer. If
however, the unit is a political entity, like a nation or a state, then definitely there
shall be inflow or outflow of water especially that of flowing surface water.
Riparian rights have to be honored and extraction of more water by the upland
unit may result in severe tension.

Note: Riparian rights mean the right of the downstream beneficiaries of a river to
the river water.

Regeneration of water within the unit

Brackish water may be converted with appropriate technology to supply sweet
water for drinking and has been tried in many extreme water scarce areas.
Waste water of households may be recycled, again with appropriate technology,
to supply water suitable for purposes like irrigation.

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1.2.4.2 The demand of water

Domestic water requirement for urban population

This is usually done through an organized municipal water distribution network.

This water is generally required for drinking, cooking, bathing and sanitary
purposes etc, for the urban areas. According to National Water Policy (2002),
domestic water supplies for urban areas under various conditions are given
below. The units mentioned “lpcd” stands for Liters per Capita per Day”.
1. 40 lpcd where only spot sources are available
2. 70 lpcd where piped water supply is available but no sewerage system
3. 125 lpcd where piped water supply and sewerage system are both
available. 150 lpcd may be allowed for metro cities.

Domestic and livestock water requirement for rural population

This may be done through individual effort of the users by tapping a local
available source or through co-operative efforts, like Panchayats or Block
Development Authorities. The accepted norms for rural water supply according
to National Water Policy (2002) under various conditions are given below.
• 40 lpcd or one hand pump for 250 persons within a walking distance of 1.6
km or elevation difference of 100 m in hills.
• 30 lpcd additional for cattle in Desert Development Programme (DDP)
areas.

Irrigation water requirement of cropped fields

Irrigation may be done through individual effort of the farmers or through group
cooperation between farmers, like Farmers’ Cooperatives. The demands have to
be estimated based on the cropping pattern, which may vary over the land unit
due to various factors like; farmer’s choice, soil type, climate, etc. Actually, the
term “Irrigation Water Demand” denotes the total quantity and the way in which a
crop requires water, from the time it is sown to the time it is harvested.

Industrial water needs

This depends on the type of industry, its magnitude and the quantity of water
required per unit of production.

1.2.5 Structural tools for water resource development

This section discusses the common structural options available to the Water
Resources Engineer to development the water potential of the region to its best
possible extent.

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Dams
These are detention structures for storing water of streams and rivers. The water
stored in the reservoir created behind the dam may be used gradually,
depending on demand.

Barrages
These are diversion structures which help to divert a portion of the stream and
river for meeting demands for irrigation or hydropower. They also help to
increase the level of the water slightly which may be advantageous from the point
of view of increasing navigability or to provide a pond from where water may be
drawn to meet domestic or industrial water demand.

Canals/Tunnels
These are conveyance structures for transporting water over long distances for
irrigation or hydropower.

These structural options are used to utilise surface water to its maximum
possible extent. Other structures for utilising ground water include rainwater
detentions tanks, wells and tube wells.

Another option that is important for any water resource project is Watershed
Management practices. Through these measures, the water falling within the
catchment area is not allowed to move quickly to drain into the rivers and
streams. This helps the rain water to saturate the soil and increase the ground
water reserve. Moreover, these measures reduce the amount of erosion taking
place on the hill slopes and thus helps in increasing the effective lives of
reservoirs which otherwise would have been silted up quickly due to the
deposition of the eroded materials.

1.2.6 Management tools for water resource planning

The following management strategies are important for water resources planning:

• Water related allocation/re-allocation agreements between planning units

sharing common water resource.
• Subsidies on water use
• Planning of releases from reservoirs over time
• Planning of withdrawal of ground water with time.
• Planning of cropping patterns of agricultural fields to optimize the water
availability from rain and irrigation (using surface and/or ground water
sources) as a function of time
• Creating public awareness to reduce wastage of water, especially filtered
drinking water and to inculcate the habit of recycling waste water for
purposes like gardening.

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 • Research in water management: Well established technological inputs are
in verge in water resources engineering which were mostly evolved over
the last century. Since, then not much of innovations have been put
forward. However, it is equally known that quite a few of these
technologies run below optimum desired efficiency. Research in this field
is essential for optimizing such structure to make most of water resource
utilization.

An example for this is the seepage loss in canals and loss of water during
application of water in irrigating the fields. As an indication, it may be pointed out
that in India, of the water that is diverted through irrigation canals up to the crop
growing fields, only about half is actually utilized for plant growth. This example
is also glaring since agriculture sector takes most of the water for its assumption
from the developed project on water resources.

A good thrust in research is needed to increase the water application efficiently

which, in turn, will help optimizing the system.

1.2.7 Inter-basin water transfer

It is possible that the water availability in a basin (Watershed) is not sufficient to
meet the maximum demands within the basin. This would require Inter-basin
water transfer, which is described below:

The National water policy adopted by the Government of India emphasizes the
need for inter-basin transfer of water in view of several water surplus and deficit
areas within the country. As early as 1980, the Minister of Water Resources had
prepared a National perspective plan for Water resources development. The
National Perspective comprises two main components:
a) Himalayan Rivers Development, and
b) Peninsular Rivers Development

Himalayan rivers development

Himalayan rivers development envisages construction of storage reservoirs on
the principal tributaries of the Ganga and the Brahamaputra in India, Nepal and
Bhutan, along with interlinking canal systems to transfer surplus flows of the
eastern tributaries of the Ganga to the west, apart from linking of the main
Brahmaputra and its tributaries with the Ganga and Ganga with Mahanadi.

Peninsular rivers development

This component is divided into four major parts:

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 1. Interlinking of Mahanadi-Godavari-Krishna-Cauvery rivers and building
storages at potential sites in these basins.
2. Interlinking of west flowing rivers, north of Mumbai and south of Tapi.
3. Interlinking of Ken-Chambal rivers.
4. Diversion of other west flowing rivers.

The possible quantity of water that may be transferred by donor basin may be
equal to the average water availability of basin minus maximum possible water
requirement within basin (considering future scenarios).

Note: A Donor basin is the basin, which is supplying the water to the
downstream basin.

The minimum expected quantity of water for recipient basin may be equal to the
minimum possible water requirement within basin (considering future scenarios)
minus average water availability of basin.

Note: A Recipient basin is the basin, which is receiving the water from the
Donor basin.

National Water Development Agency (NWDA) of the Government of India has

been entrusted with the task of formalizing the inter-linking proposal in India. So
far, the agency has identified some thirty possible links within India for inter-basin
transfer based on extensive study of water availability and demand data.

Note:
The National Water Development Agency (NWDA) was set up in July, 1982 as
an Autonomous Society under the Societies Registration Act, 1960, to carry out
the water balance and other studies on a scientific and realistic basis for optimum
utilization of Water Resources of the Peninsular rivers system for preparation of
feasibility reports and thus to give concrete shape to Peninsular Rivers
Development Component of National Perspective. In 1990, NWDA was also
entrusted with the task of Himalayan Rivers Development Component of National
Perspective.

Possible components of an inter-basin transfer project include the following:

• Storage Dam in Donor basin to store flood runoff
• Conveyance structure, like canal, to transfer water from donor to recipient
basin
• Possible pumping equipments to raise water across watershed-divide

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Possible implications of inter-basin transfer: Since a large scale water transfer
would be required, it is necessary to check whether there shall be any of the
following:

• River bed level rise or fall due to possible silt deposition or removal.
• Ground water rise or fall due to possible excess or deficit water seepage.
• Ecological imbalance due to possible disturbance of flora and fauna
habitat.
• Desertification due to prevention of natural flooding (i.e. by diversion of
flood water)
• Transfer of dissolved salts, suspended sediments, nutrients, trace
elements etc. from one basin to another.

1.2.8 Tasks for planning a water resources project

The important tasks for preparing a planning report of a water resources project
would include the following:

• Analysis of basic data like maps, remote sensing images, geological data,
hydrologic data, and requirement of water use data, etc.
• Selection of alternative sites based on economic aspects generally, but
keeping in mind environmental degradation aspects.
• Studies for dam, reservoir, diversion structure, conveyance structure, etc.
- Selection of capacity.
- Selection of type of dam and spillway.
- Layout of structures.
- Analysis of foundation of structures.
- Development of construction plan.
- Cost estimates of structures, foundation strengthening measures,
etc.
• Studies for local protective works – levees, riverbank revetment, etc.
• Formulation of optimal combination of structural and non-structural
components (for projects with flood control component).
• Economic and financial analyses, taking into account environmental
degradation, if any, as a cost.
• Environmental and sociological impact assessment.

Of the tasks mentioned above, the first five shall be dealt with in detail in this
course. However, we may mention briefly the last two before closing this
chapter.

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1.2.9 Engineering economy in water resources planning
All Water Resources projects have to be cost evaluated. This is an essential part
of planning. Since, generally, such projects would be funded by the respective
State Governments, in which the project would be coming up it would be helpful
for the State planners to collect the desired amount of money, like by issuing
bonds to the public, taking loans from a bank, etc. Since a project involves
money, it is essential that the minimum amount is spent, under the given
constraints of project construction. Hence, a few feasible alternatives for a project
are usually worked out. For example, a project involving a storage dam has to be
located on a map of the river valley at more than one possible location, if the
terrain permits. In this instance, the dam would generally be located at the
narrowest part of the river valley to reduce cost of dam construction, but also a
couple of more alternatives would be selected since there would be other
features of a dam whose cost would dictate the total cost of the project. For
example, the foundation could be weak for the first alternative and consequently
require costly found treatment, raising thereby the total project cost. At times, a
economically lucrative project site may be causing submergence of a costly
property, say an industry, whose relocation cost would offset the benefit of the
alternative. On the other hand, the beneficial returns may also vary. For example,
the volume of water stored behind a dam for one alternative of layout may not be
the same as that behind another. Hence, what is required is to evaluate the so-
called Benefit-Cost Ratio defined as below:

AnnualBenefits ( B)
Benefit − CostRatio =
AnnualCost (C )
The annual cost and benefits are worked out as under.

Annual Cost (C): The investment for a project is done in the initial years during
construction and then on operation and maintenance during the project's lifetime.
The initial cost may be met by certain sources like borrowing, etc. but has to be
repaid over a certain number of years, usually with an interest, to the lender. This
is called the Annual Recovery Cost, which, together with the yearly maintenance
cost would give the total Annual Costs. It must be noted that there are many non-
tangible costs, which arise due to the effect of the project on the environment that
has to be quantified properly and included in the annual costs.

1.2.10 Assessment of effect on environment and society

This is a very important issue and all projects need to have clearance from the
Ministry of Environment and Forests on aspects of impact that the project is likely
to have on the environment as well as on the social fabric. Some of the adverse
(negative) impacts, for which steps have to be taken, are as follows:

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 • Loss of flora and fauna due to submergence.
• Loss of land having agricultural, residential, industrial, religious,
archaeological
importance.
• Rehabilitation of displaced persons.
• Reservoir induced seismicity.
• Ill-effect on riverine habitats of fish due to blockage of the free river
passage

There would also be some beneficial (positive) impacts of the project, like
improvement of public health due to availability of assured, clean and safe
drinking water, assured agricultural production, etc. There could even be an
improvement in the micro-climate of the region due to the presence of a water
body.

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 Module
1
Principles of Water
Resources Engineering
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 Lesson
3
National Policy For
Water Resources
Development

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Instructional Objectives
On completion of this lesson, the student shall be able to:
1. Appreciate the policy envisaged by the nation to develop water resources
within the country
2. Conventional and non-conventional methods in planning water resources
projects
3. Priorities in terms of allocation of water for various purposes
4. Planning strategies and alternatives that should be considered while
developing a particular project
5. Management strategies for excess and deficit water imbalances
6. Guidelines for projects to supply water for drinking and irrigation
7. Participatory approach to water management
8. Importance of monitoring and maintaining water quality of surface and
ground water sources.
9. Research and development which areas of water resources engineering
need active
10. Agencies responsible for implementing water resources projects in our
country
11. Constitutional provision guiding water resource development in the county
12. Agencies responsible for monitoring the water wealth of the country and
plan scientific development based on the National Policy on water

1.3.0 Introduction
Water, though commonly occurring in nature, is invaluable! It supports all forms
of life in conjunction with air. However, the demand of water for human use has
been steadily increasing over the past few decades due to increase in
population. In contrast, the total reserve of water cannot increase. Hence each
nation, and especially those with rapidly increasing population like India, has to
think ahead for future such that there is equitable water for all in the years to
come. This is rather difficult to achieve as the water wealth varies widely within a
country with vast geographical expanse, like India. Moreover, many rivers
originate in India and flow through other nations (Pakistan and Bangladesh) and

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the demands of water in those counties have to be honored before taking up a
project on such a river. Similarly there are rivers which originate form other
counties (Nepal, Bhutan and China) and flow through India.

All these constraints have led to the formulation of the national water policy which
was drafted in 1987 keeping in mind national perspective on water resource
planning, development and management. The policy has been revised in 2002,
keeping in mind latest objectives. It is important to know the essentials of the
national policy as it has significant bearing on the technology or engineering that
would be applied in developing and managing water resources projects.

This section elucidates the broad guidelines laid own in the National Water Policy
(2002) which should be kept in mind while planning any water resource project in
our country.

1.3.1 Water Resources Planning

Water resources development and management will have to be planned for a
hydrological unit such as a drainage basin as a whole or a sub-basin. Apart from
traditional methods, non-conventional methods for utilization of water should be
considered, like
• Inter-basin transfer
• Artificial recharge of ground water
• Desalination of brackish sea water
• Roof-top rain water harvesting

The above options are described below in some detail:

Inter-basin transfer: Basically, it's the movement of surface water from one river
basin into another. The actual transfer is the amount of water not returned to its
source basin. The most typical situation occurs when a water system has an
intake and wastewater discharge in different basins. But other situations also
cause transfers. One is where a system's service area covers more than one
basin. Any water used up or consumed in a portion of the service area outside of
the source basin would be considered part of a transfer (e.g. watering your yard).
Transfers can also occur between interconnected systems, where a system in
one basin purchases water from a system in another basin.

Artificial recharge of ground water: Artificial recharge provides ground water

users an opportunity to increase the amount of water available during periods of
high demand--typically summer months. Past interest in artificial recharge has
focused on aquifers that have declined because of heavy use and from which
existing users have been unable to obtain sufficient water to satisfy their needs.

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Desalination of brackish sea water: Water seems to be a superabundant
natural resource on the planet earth. However, only 0.3 per cent of the world's
total amount of water can be used as clean drinking water. Man requires huge
amounts of drinking water every day and extracts it from nature for innumerable
purposes. As natural fresh water resources are limited, sea water plays an
important part as a source for drinking water as well. In order to use this water, it
has to be desalinated. Reverse osmosis and electro dialysis is the preferred
methods for desalination of brackish sea water.

Roof-top rain water harvesting: In urban areas, the roof top rain water can be
conserved and used for recharge of ground water. This approach requires
connecting the outlets pipe from roof top to divert the water to either existing
well/tube wells/bore wells or specially designed wells/ structures. The Urban
housing complexes or institutional buildings have large roof area and can be
utilized for harvesting the roof top rain water to recharge aquifer in urban areas.

One important concept useful in water resources planning is Conjunctive or

combined use of both surface and ground water for a region has to be planned
for sustainable development incorporating quantity and quality aspects as well as
environmental considerations. Since there would be many factors influencing the
decision of projects involving conjunctive use of surface and ground water,
keeping in mind the underlying constraints, the entire system dynamics should be
studied to as detail as practically possible. The uncertainties of rainfall, the
primary source of water, and its variability in space and time has to be borne in
mind while deciding upon the planning alternatives.

It is also important to pursue watershed management through the following

methodologies:

• Soil conservation
This includes a variety of methods used to reduce soil erosion, to prevent
depletion of soil nutrients and soil moisture, and to enrich the nutrient
status of a soil.

• Catchment area treatment

Different methods like protection for degradation and treating the
degraded areas of the catchment areas, forestation of catchment area.

• Construction of check-dams
Check-dams are small barriers built across the direction of water flow on
shallow rivers and streams for the purpose of water harvesting. The small
dams retain excess water flow during monsoon rains in a small catchment
area behind the structure. Pressure created in the catchment area helps
force the impounded water into the ground. The major environmental
benefit is the replenishment of nearby groundwater reserves and wells.
The water entrapped by the dam, surface and subsurface, is primarily

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 intended for use in irrigation during the monsoon and later during the dry
season, but can also be used for livestock and domestic needs.

1.3.2 Water allocation priorities

While planning and operation of water resource systems, water allocation
priorities should be broadly as follows:
• Drinking water
• Irrigation
• Hydropower
• Ecology
• Industrial demand of water
• Navigation

The above demands of water to various sectors are explained in the following
paragraphs.

Drinking water: Adequate safe drinking water facilities should be provided to the
entire population both in urban and in rural areas. Irrigation and multipurpose
projects should invariably include a drinking water component, wherever there is
no alternative source of drinking water. Drinking water needs of human beings
and animals should be the first charge on any available water.

Irrigation: Irrigation is the application of water to soil to assist in the production

of crops. Irrigation water is supplied to supplement the water available from
rainfall and ground water. In many areas of the world, the amount and timing of
the rainfall are not adequate to meet the moisture requirements of crops. The
pressure for survival and the need for additional food supplies are causing the
rapid expansion of irrigation throughout the world.

Hydropower: Hydropower is a clean, renewable and reliable energy source that

serves national environmental and energy policy objectives. Hydropower
converts kinetic energy from falling water into electricity without consuming more
water than is produced by nature.

Ecology: The study of the factors that influence the distribution and abundance
of species.

Industrial demand of water: Industrial water consumption consists of a wide

range of uses, including product-processing and small-scale equipment cooling,
sanitation, and air conditioning. The presence of industries in or near the city has
great impact on water demand. The quantity of water required depends on the
type of the industry. For a city with moderate factories, a provision of 20 to 25
percent of per capita consumption may be made for this purpose.

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Navigation: Navigation is the type of transportation of men and goods from one
place to another place by means of water. The development of inland water
transport or navigation is of crucial importance from the point of energy
conservation as well.

1.3.3 Planning strategies for a particular project

Water resource development projects should be planned and developed (as far
as possible) as multi-purpose projects . The study of likely impact of a project
during construction and later on human lives, settlements, socio-economic,
environment, etc., has to be carried out before hand. Planning of projects in the
hilly areas should take into account the need to provide assured drinking water,
possibilities of hydropower development and irrigation in such areas considering
the physical features and constraints of the basin such as steep slopes, rapid
runoff and possibility of soil erosion.

As for ground water development there should be a periodical reassessment of

the ground water potential on a scientific basis, taking into consideration the
quality of the water available and economic viability of its extraction. Exploitation
of ground water resources should be so regulated as not to exceed the
recharging possibilities, as also to ensure social equity. This engineering aspect
of ground water development has been dealt with in Lesson 8.1.

Planning at river basin level requires considering a complex large set of

components and their interrelationship. Mathematical modelling has become a
widely used tool to handle such complexities for which simulations and
optimization techniques are employed. One of the public domain software
programs available for carrying out such tasks is provided by the United States
Geological Survey at the following web-site http://water.usgs.gov/software/. The
software packages in the web-site are arranged in the following categories:

• Ground Water
• Surface Water
• Geochemical
• General Use
• Statistics & Graphics

There are private companies who develop and sell software packages. Amongst
these, the DHI of Denmark and Delft Hydraulics of Netherlands provide
comprehensive packages for many water resources applications.

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Note:
Multi-purpose projects: Many hydraulic projects can serve more than one of the
basic purposes-water supply, irrigation, hydroelectric power, navigation, flood
control, recreation, sanitation and wild life conservation. Multiple use of project of
facilities may increase benefits without a proportional increase in costs and thus
enhance the economic justification for the project. A project which is which is
designed for single purpose but which produces incidental benefits for other
purposes should not, however, be considered a multi-purpose project. Only those
projects which are designed and operated to serve two or more purposes should
be described as multi-purpose.

1.3.4 Guidelines for drinking and irrigation water projects

The general guidelines for water usage in different sectors are given below:

1.3.4.1 Drinking water

Adequate safe drinking water facilities should be provided to the entire population
both in urban and rural areas. Irrigation and multi purpose projects should
invariably include a drinking water component wherever there is no alternative
source of drinking water.

Primarily, the water stored in a reservoir has to be extracted using a suitable

pumping unit and then conveyed to a water treatment plant where the physical
and chemical impurities are removed to the extent of human tolerance. The
purified water is then pumped again to the demand area, that is, the urban or
rural habitation clusters. The source of water, however, could as well be from
ground water or directly from the river.

The aspect of water withdrawal for drinking and its subsequent purification and
distribution to households is dealt with under the course Water and Waste Water
Engineering. The following books may be useful to consult.
• Waster Water Engineering by B C Punmia and A K jain
• Water and waste water engineering by S P Garg

1.3.4.2 Irrigation

Irrigation planning either in an individual project or in a basin as whole should

take into account the irrigability of land, cost of effective irrigation options
possible from all available sources of water and appropriate irrigation techniques
for optimizing water use efficiency. Irrigation intensity should be such as to
extend the benefits of irrigation to as large as number of farm families as
possible, keeping in view the need to maximize production.

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 • Water allocation in an irrigation system should be done with due regard
to equity and social justice. Disparities in the availability of water between
head-reach and tail-end farms and (in respect of canal irrigation) between
large and small farms should be obviated by adoption of a rotational
water distribution system and supply of water on a volumetric basis
subject to certain ceilings and rational water pricing.

• Concerned efforts should be made to ensure that the irrigation potential

created is fully utilized. For this purpose, the command area
development approach should be adopted in all irrigation projects.

• Irrigation being the largest consumer of freshwater, the aim should be to

get optimal productivity per unit of water. Scientific water management,
farm practices and sprinkler and drip system of irrigation should be
adopted wherever possible.

The engineering aspects of irrigation engineering have been discussed in

Section 6.

Some terms defined in the above passages are explained below:

Water allocation: Research on institutional arrangements for water allocation

covers three major types of water allocation: public allocation, user-based
allocation, and market allocation. This work includes attention to water rights and
to the organizations involved in water allocation and management, as well as a
comparative study of the consequences of water reallocation from irrigation to
other sectors. A key aspect of this research is the identification of different
stakeholders' interests, and the consequences of alternative institutions for the
livelihoods of the poor.

Rotational water distribution system: Water allocated to the forms one after
the other in a repeated manner.

Volumetric basis: Water allocated to each farm a specified volume based on

the area of the farm, type of crop etc.

Irrigation Potential: Irrigation is the process by which water is diverted from a

river or pumped from a well and used for the purpose of agricultural production.
Areas under irrigation thus include areas equipped for full and partial control
irrigation, spate irrigation areas, equipped wetland and inland valley bottoms,
irrespective of their size or management type. It does not consider techniques
related to on-farm water conservation like water harvesting. The area which can
potentially be irrigated depends on the physical resources 'soil' and 'water',
combined with the irrigation water requirements as determined by the cropping
patterns and climate. However, environmental and socioeconomic constraints

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also have to be taken into consideration in order to guarantee a sustainable use
of the available physical resources. This means that in most cases the
possibilities for irrigation development would be less than the physical irrigation
potential.

Command area development: The command area development programme

aims mainly at reducing the gap between the potential created for irrigation to
achieve higher agriculture production thereof. This is to be achieved through the
integrated development of irrigated tracks to ensure efficient soil land use and
water management for ensuring planned increased productivity.

Sprinkler irrigation: Sprinkler irrigation offers a means of irrigating areas which

are so irregular that they prevent use of any surface irrigation methods. By using
a low supply rate, deep percolation or surface runoff and erosion can be
minimized. Offsetting these advantages is the relatively high cost of the sprinkling
equipment and the permanent installations necessary to supply water to the
sprinkler lines. Very low delivery rates may also result in fairly high evaporation
from the spray and the wetted vegetation. It is impossible to get completely
uniform distribution of water around a sprinkler head and spacing of the heads
must be planned to overlap spray areas so that distribution is essentially uniform.

Drip: The drip method of irrigation, also called trickle irrigation, originally
developed in Israel, is becoming popular in areas having water scarcity and salt
problems. The method is one of the most recent developments in irrigation. It
involves slow and frequent application of water to the plant root zone and
enables the application of water and fertilizer at optimum rates to the root
system. It minimizes the loss of water by deep percolation below the root zone or
by evaporation from the soil surface. Drip irrigation is not only economical in
water use but also gives higher yields with poor quality water.

1.3.5 Participatory approach to water resource management

Management of water resources for diverse uses should incorporate a
participatory approach; by involving not only the various government agencies
but also the users and other stakeholders in various aspects of planning, design,
development and management of the water resources schemes. Even private
sector participation should be encouraged, wherever feasible.

In fact, private participation has grown rapidly in many sectors in the recent years
due to government encouragement. The concept of “Build-Own-Transfer (BOT)”
has been popularized and shown promising results. The same concept may be
actively propagated in water resources sector too. For example, in water scarce
regions, recycling of waste water or desalinization of brackish water, which are

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more capital intensive (due to costly technological input), may be handed over to
private entrepreneurs on BOT basis.

1.3.6 Water quality

The following points should be kept in mind regarding the quality of water:

1. Both surface water and ground water should be regularly monitored for
quality.
2. Effluents should be treated to acceptable levels and standards before
discharging them into natural steams.
3. Minimum flow should be ensured in the perennial streams for maintaining
ecology and social considerations.

Since each of these aspects form an important segment of water resources

engineering, this has been dealt separately in course under water and waste
water engineering.

The technical aspects of water quality monitoring and remediation are dealt with
in the course of Water and Waste – Water Engineering. Knowledge of it is
essential for the water resources engineer to know the issues involved since,
even polluted water returns to global or national water content.

Monitoring of surface and ground water quality is routinely done by the Central
and State Pollution Control Boards. Normally the physical, chemical and
biological parameters are checked which gives an indication towards the
acceptability of the water for drinking or irrigation. Unacceptable pollutants may
require remediation, provided it is cost effective. Else, a separate source may
have to be investigated. Even industrial water also require a standard to be met,
for example, in order to avoid scale formation within boilers in thermal power
projects hard water sources are avoided.

The requirement of effluent treatment lies with the users of water and they should
ensure that the waste water discharged back to the natural streams should be
within acceptable limits. It must be remembered that the same river may act as
source of drinking water for the inhabitants located down the river. The following
case study may provoke some soul searching in terms of the peoples’
responsibility towards preserving the quality of water, in our country:

Under the Ganga Action Plan (GAP) initiated by the government to clean the
heavily polluted river, number of Sewage Treatment Plants (STPs) have been
constructed all along the river Ganga. The government is also laying the main
sewer lines within towns that discharge effluents into the river. It is up to the
individual house holders to connect their residence sewer lines up to the trunk

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sewer, at some places with government subsidy. However, public apathy in
many places has resulted in only a fraction of the houses being connected to the
trunk sewer line which has resulted in the STPs being run much below their
capacity.

Lastly, it must be appreciated that a minimum flow in the rivers and streams,
even during the low rainfall periods is essential to maintain the ecology of the
river and its surrounding as well as the demands of the inhabitants located on the
downstream. It is a fact that excessive and indiscriminate withdrawal of water
has been the cause of drying up of many hill streams, as for example, in the
Mussourie area. It is essential that the decision makers on water usage should
ensure that the present usage should not be at the cost of a future sacrifice.
Hence, the policy should be towards a sustainable water resource development.

1.3.7 Management strategies for excess and deficit water

imbalances
Water is essential for life. However, if it is present in excess or deficit quantities
than that required for normal life sustenance, it may cause either flood or
drought. This section deals with some issues related to the above imbalance of
water, and strategies to mitigate consequential implications. Much detailed
discussions is presented in Lesson 6.2.

1.3.7.1 Flood control and management

• There should be a master plan for flood control and management for each
flood prone basin.
• Adequate flood-cushioning should be provided in water storage projects,
wherever feasible, to facilitate better flood management.
• While physical flood protection works like embankments and dykes will
continue to be necessary, increased emphasis should be laid on non-
structural measures such as flood forecasting and warning, flood plain
zoning, and flood proofing for minimization of losses and to reduce the
recurring expenditure on flood relief.

1.3.7.2 Drought prone area development

• Drought-prone areas should be made less vulnerable to drought

associated problems through soil conservation measures, water
harvesting practices, minimization of evaporation losses, and
development of ground water potential including recharging and
transfer of surface water from surplus areas where feasible and
appropriate.

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Terms referred to above are explained below:

Flood cushioning: The reservoirs created behind dams may be emptied to

some extent, depending on the forecast of impending flood, so that as and when
the flood arrives, some of the water gets stored in the reservoir, thus reducing the
severity of the flood.

Embankments and dykes: Embankments & dykes also known as levees are
earthen banks constructed parallel to the course of river to confine it to a fixed
course and limited cross-sectional width. The heights of levees will be higher
than the design flood level with sufficient free board. The confinement of the river
to a fixed path frees large tracts of land from inundation and consequent
damage.

Flood forecast and warning: Forecasting of floods in advance enables a

warning to be given to the people likely to be affected and further enables civil-
defence measures to be organized. It thus forms a very important and relatively
inexpensive nonstructural flood-control measure. However, it must be realized
that a flood warning is meaningful if it is given sufficiently in advance. Also,
erroneous warnings will cause the populace to loose faith in the system. Thus the
dual requirements of reliability and advance notice are the essential ingredients
of a flood-forecasting system.

Flood plain zoning: One of the best ways to prevent trouble is to avoid it and
one of the best ways to avoid flood damage is to stay out of the flood plain of
streams. One of the forms of the zoning is to control the type, construction and
use of buildings within their limits by zoning ordinances. Similar ordinances might
prescribe areas within which structures which would suffer from floods may not
be built. An indirect form of zoning is the creation of parks along streams where
frequent flooding makes other uses impracticable.

Flood proofing: In instances where only isolated units of high value are
threatened by flooding, they may sometimes by individually flood proofed. An
industrial plant comprising buildings, storage yards, roads, etc., may be protected
by a ring levee or flood wall. Individual buildings sufficiently strong to resist the
dynamic forces of the flood water are sometimes protected by building the lower
stories (below the expected high-water mark) without windows and providing
some means of watertight closure for the doors. Thus, even though the building
may be surrounded by water, the property within it is protected from damage and
many normal functions may be carried on.

Soil conservation measures: Soil conservation measures in the catchment

when properly planned and effected lead to an all-round improvement in the
catchment characteristics affecting abstractions. Increased infiltration, greater
evapotranspiration and reduced soil erosion are some of its easily identifiable
results. It is believed that while small and medium floods are reduced by soil

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conservation measures, the magnitude of extreme floods are unlikely to be
affected by these measures.

Water harvesting practices: Technically speaking, water harvesting means

capturing the rain where it falls, or capturing the run-off in one’s own village or
town. Experts suggest various ways of harvesting water:

• Capturing run-off from rooftops;

• Capturing run-off from local catchments;
• Capturing seasonal flood water from local streams; and
• Conserving water through watershed management.

Apart from increasing the availability of water, local water harvesting systems
developed by local communities and households can reduce the pressure on the
state to provide all the financial resources needed for water supply. Also,
involving people will give them a sense of ownership and reduce the burden on
government funds.

Minimization of evaporation losses: The rate of evaporation is dependent on

the vapour pressures at the water surface and air above, air and water
temperatures, wind speed, atmospheric pressure, quality of water, and size of
the water body. Evaporation losses can be minimized by constructing deep
reservoirs, growing tall trees on the windward side of the reservoir, plantation in
the area adjoining the reservoir, removing weeds and water plants from the
reservoir periphery and surface, releasing warm water and spraying chemicals or
fatty acids over the water surface.

Development of groundwater potential: A precise quantitative inventory

regarding the ground-water reserves is not available. Organization such as the
Geographical Survey of India, the Central Ground-Water Board and the State
Tube-Wells and the Ground-Water Boards are engaged in this task. It has been
estimated by the Central Ground-Water Board that the total ground water
reserves are on the order of 55,000,000 million cubic meters out of which
425,740 million cubic meters have been assessed as the annual recharge from
rain and canal seepage. The Task Force on Ground-Water Reserves of the
Planning Commission has also endorsed these estimates. All recharge to the
ground-water is not available for withdrawal, since part of it is lost as sub-surface
flow. After accounting from these losses, the gross available ground-water
recharge is about 269,960 million cubic meters per annum. A part of this
recharge (2,460 million cubic meters) is in the saline regions of the country and is
unsuitable for use in agriculture owing to its poor quality. The net recharge
available for ground-water development in India, therefore, is of the magnitude of
about 267,500 million cubic meters per annum. The Working Group of the
Planning Commission Task Force Ground-Water Reserves estimated that the
usable ground-water potential would be only 75 to 80 per cent of the net ground-
water recharge available and recommended a figure of 203,600 million cubic

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meters per annum as the long-term potential for ground-water development in
India.

Recharging: Artificial recharge provides ground water users an opportunity to

increase the amount of water available during periods of high demand--typically
summer months. Past interest in artificial recharge has focused on aquifers that
have declined because of heavy use and from which existing users have been
unable to obtain sufficient water to satisfy their needs.

Transfer of surface water: Basically, it's the movement of surface water from
one river basin into another. The actual transfer is the amount of water not
returned to its source basin. The most typical situation occurs when a water
system has an intake and wastewater discharge in different basins. But other
situations also cause transfers. One is where a system's service area covers
more than one basin. Any water used up or consumed in a portion of the service
area outside of the source basin would be considered part of a transfer (e.g.
watering your yard). Transfers can also occur between interconnected systems,
where a system in one basin purchases water from a system in another basin.

1.3.8 Implementation of water resources projects

Water being a state subject, the state governments has primary responsibility for
use and control of this resource. The administrative control and responsibility for
development of water rests with the various state departments and corporations.
Major and medium irrigation is handled by the irrigation / water resources
departments. Minor irrigation is looked after partly by water resources
department, minor irrigation corporations and zilla parishads / panchayats and by
other departments such as agriculture. Urban water supply is generally the
responsibility of public health departments and panchayatas take care of rural
water supply. Government tube-wells are constructed and managed by the
irrigation/water resources department or by the tube-well corporations set up for
the purpose. Hydropower is the responsibility of the state electricity boards.

Due to the shared responsibilities, as mentioned above, for the development of

water resources projects there have been instances of conflicting interests
amongst various state holders.

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1.3.9 Constitutional provisions for water resources
development
India is a union of states. The Constitutional provisions in respect of allocation of
responsibilities between the State and Center fall into three categories: the Union
List (List-I), the State List (List-II) and the Concurrent List (List-III). Article 246 of
the Constitution deals with subject matter of laws to be made by the Parliament
and by Legislature of the States. As most of the rivers in the country are inter-
State, the regulation and development of waters of these rivers is a source of
inter-State differences and disputes. In the Constitution, water is a matter
included in entry 17 of List-II i.e., State List. This entry is subject to provision of
entry 56 of List-I i.e., Union List. The specific provisions in this regard are as
under:

• Article 246
Notwithstanding anything in clauses (2) and (3), Parliament has exclusive
power to make laws with respect to any of the matters enumerated in List-I
in the seventh schedule (in this Constitution referred to as the “Union
List”).
1) Notwithstanding anything in clauses (3), Parliament, and, subject to
clause (1), the Legislature of any State also, have power to make
laws with respect to any of the matters enumerated in List-III in the
seventh schedule (in this Constitution referred to as the “Concurrent
List”).
2) Subject to clauses (1) and (2), the Legislature of any state has
exclusive power to make laws for such state or any part thereof with
respect to any of the matters enumerated in List-II in the seventh
schedule (in this Constitution referred to as the “State List”).
3) Parliament has power to make laws with respect to any matter for
any part of the territory of India not included in a State
notwithstanding that such matter is a matter enumerated in the State
List.

• Article 262
In case of disputes relating to waters, article 262 provides:
1) Parliament may by law provide for the adjudication of any dispute or
complaint with respect to the use, distribution or control of the waters
of, or in, any inter-State river or river-valley.
2) Notwithstanding anything in this Constitution, Parliament may, by law
provide that neither the Supreme Court nor any other Court shall
exercise jurisdiction in respect of any such dispute or complaint as is
referred to in clause (1).

• Entry 56 of list I of seventh schedule

Entry 56 of List I of seventh schedule provides that “Regulation and
development of inter-State rivers and river valleys to the extent to which
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 such regulation and development under the control of the Union are
declared by Parliament by law to be expedient in the public interest”.

• Entry 17 under list II of seventh schedule

Entry 17 under List II of seventh schedule provides that “Water, that is to
say, water supplies, irrigation and canals, drainage and embankments,
water storage and water power subjects to the provisions of entry 56 of
List I”.
As such, the Central Government is conferred with powers to regulate and
develop inter-State rivers under entry 56 of List I of seventh schedule to
the extent declared by the Parliament by law to be expedient in the public
interest.
It also has the power to make laws for the adjudication of any dispute
relating to waters of Inter-State River or river valley under article 262 of
the Constitution.

1.3.10 Central agencies in water resources sector

Some of the important offices working under the Ministry of Water Resources,
Government of India (website of the ministry: http://wrmin.nic.in) which plays key
role in assessing, planning and developing the water resources of the country are
as follows:

• Central Water Commission (CWC)

• Central Ground Water Board (CGWB)
• National Water Development Agency (NWDA)
• Brahmaputra Board
• Central Water and Power Research Station (CWPRS)
• Central Soil and Materials Research Station (CSMRS)
• National Institute of Hydrology (NIH)
• Ganga Flood Control Commission (GFCC)
• Water and Power Consultancy Services (India) ltd (WAPCOS)
• National Projects Construction Corporation ltd (NPCC)

Detailed activities of the above departments may be obtained from the Ministry of
Water Resources web-site.

Although not directly under the ministry of water resources, the National
Hydropower Corporation (NHPC) as well as Rail India Technical Engineers
Services (RITES) also actively participate in water resources development
projects.

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 Module
1
Principles of Water
Resources Engineering
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 Lesson
4
Planning and
Assessment of Data for
Project Formulation

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Instructional Objectives
On completion of this lesson, the student shall be able to learn:
1. The range of water resources project and the general planning philosophy
2. Planning arrangements for drinking water supply project and related data
requirement
3. Planning arrangements for irrigation water supply project and related data
requirement
4. Planning arrangements for hydropower generation project and related
data requirement
5. Planning arrangements for flood control project and related data
requirement
6. Investigations for data assessment for constructing water resource
engineering structures
7. Water availability computations
8. Data collection for environment, socio-economic and demographic
informations
9. Data collection methods for topography, geology, rainfall and stream flow.

1.4.0 Introduction
A water resources systems planner is faced with the challenge of conceptualizing
a project to meet the specific needs at a minimum cost. For a demand intensive
project, the size of the project is limited by the availability of water. The planner
then has to choose amongst the alternatives and determine the optimum scale of
the project. If it is a multi-purpose project, an allocation of costs has to be made
to those who benefit from the project. An important aspect of planning is that it
has to prepare for a future date – its effects in terms of physical quantities and
costs over a period of time spanning the useful life of project has to be evaluated.
The return expected over the project period has to be calculated.

All this requires broader decisions, which affect the design details of the project.
This chapter looks into the different aspects of preparing a project plan likely to
face a water resources system planner, including the basic assessment of data
that is primary to any project plan formulation.

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1.4.1 Meeting the challenges

The major projects which water resources systems planner has to conceptualize
are shown in Figure 1. Although the figure shows each project to be separate
entity, quite a few real projects may actually serve more than one purpose. For
example, the Hirakud or the Bhakra dams cater to flood control, irrigation and
hydropower generation. On the other hand more than one project is necessary
(and which actually forms a system of projects) to achieve a specific purpose.

For example, to control the floods in the Damodar River, which earlier used to
havoc in the districts of Bardhaman, Hooghly and Howrah in West Bengal, a
number of dams were constructed on the Damodar and its tributaries between
1950s and 1970. For irrigation projects, a dam may be constructed across a
river to store water in the upstream reach and a barrage may be constructed in
the downstream reach to divert and regulate the water through an off taking
canal.

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1.4.2 Project planning for domestic water supply
The project for supplying drinking water to a township would usually consist of a
network of pipelines to reach the demand area. The source of water could be
underground or from a surface water body, usually a river. At times, it could be a
judicious combination of the two. A water resources systems planner has to
design the whole system from the source up to the distribution network.
However, the scope of water resources engineering is generally be limited to the
intake system design. The storage of water, its treatment and finally distribution
to the consumers are looked after by the authorities of the township. Further
details may be obtained in a course on Water and Waste Water Engineering.

Typical intake systems could possibly be one of the following, depending and the
convenience of planning.

1. Construction of a water intake plant directly from the river

Example: Water intake system at Palta for Kolkata from river
Hooghly.

2. Construction of a dam across a river and drawing water from the reservoir
behind.
Example: Dam at Mawphlang on river Umiam for water supply to
Shillong.

3. Construction of a barrage across a river and drawing water from the pool
behind
Example: Wazirabad barrage across river Yamuna for water
supply to Delhi.

4. Construction of infiltration wells near a river to draw riverbed ground water

Example: For water supply to IIT Kharagpur campus from river
Kangsabati.

5. Construction of deep wells to draw water from lower strata of ground water
Example: Water intake system for the city of Barddhaman.

A simple line sketch is shown in Figure 2 to show the processes for intake,
storage, treatment and distribution of a typical drinking water project.

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1.4.3 Data requirement for domestic water supply project
The following data is required for planning and designing a typical water supply
system.

1.4.3.1 Demand of water

As discussed in lesson 1.2, according to the norms laid out in the National
Building Code, and revised under National Water policy (2002), the following
demand of domestic water consumption may be adopted:

Rural water supply:

• 40 litres per capita per day or one hand pump 250 persons within
walking distance of 1.6 km or elevation difference of 100m in hills
• 30 lpcd additional for cattle in desert development programmed
areas
Urban water supply:
• 40 lpcd where only sources are available
• 70 lpcd where piped water supply is available but no sewerage
system
• 125 lpcd where piped water supply and sewerage system are both
available.
• 150 lpcd for main cities

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 • Additional water for other demands like commercial, institutional,
firefighting, gardening, etc.

Since the water supply project would serve a future population, a realistic
projection has to be made based on scientific projection methods like

• Arithmetic increase method.

• Geometric increase method.
• Incremental increase method.

Water supply projects, under normal circumstances, may be designed for a

period of thirty years. This period may be modified in regard to certain
components of the project, depending upon:
• The useful life of the component facility
• Ease in carrying out extensions, when required.
• Rate of interest.

1.4.3.2 Availability of water and other data

The availability of water has been discussed in a subsequent section of this

lesson, which would be used to design the capacities of the intake by the water
resources engineer, by comparing with the demand. The data for constructing
the structures would usually be topography for locating the structure, geology for
finding foundation characteristics and materials required for construction of the
structure.

1.4.4 Project planning for irrigation water supply

The project may consist of supplying water to irrigate an area through a network
of canals, by diverting some of the water from a river by constructing a barrage
for water diversion and head regulator for water control. The water through
canals mostly flows by gravity (except for pumped canal projects), the area under
cultivation by the water of the canal is called the Command Area. This area is
decided by the prevailing slope of the land. Although the main source of water for
irrigating an area could be surface water, it could be supplemented with ground
water. This combination of surface and ground water for irrigation is known as
Conjunctive use.

The principal component of an irrigation scheme is a diversion structure – a weir

or a barrage – though the latter is preferred in a modern irrigation project. Since
the height of such a structure is rather small compared to that of a dam, the
volume of water stored behind a barrage (the barrage pool) is small compared to
that stored behind a dam (the dam reservoir). The elevated water surface of the

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barrage pool causes the water to be diverted into the canal, the entry of which is
regulated through a canal head works. If the river is perennial, and the minimum
flow of the river is sufficient to cater to the flow through the canal, this
arrangement is perfectly fine to irrigate a command area using a barrage and an
irrigation canal system. However, if the river is non-perennial, or the minimum
flow of the river is less than the canal water demand, then a dam may be
constructed at a suitable upstream location of the river. This would be useful in
storing larger volumes, especially the flood water, of water which may be
released gradually during the low-flow months of the river.

A conceptual scheme of a diversion scheme for irrigation is shown in Figure 3.

1.4.5 Data requirement for water supply to an irrigation

project
The following data is required for planning and designing a typical irrigation
system.

1.4.5.1 Demand of water for irrigation water supply

The demand of water for an irrigation scheme is to be calculated from the

cropping schedule that is proposed in the Command Area. Different crops have

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different water requirements and their demand also varies with the growth of the
plants. Further, Command Area may be able to cultivate more than one crop
within since many of the crops have maturity duration of few months.

The field requirement decides the design discharge for the distributaries and so
on up to the canal regulator. Of course, most canals are prone to losses with
water seeping through the canal sides. Exceptions are the lined canals, though
in this case, the loss of infiltrating water is very small. Thus the net demand at the
head of the canal system, as a function of time, is calculated. Lessons of Module
3 deal in detail about the irrigation system demand of water.

1.4.5.2 Availability of water and other data

This has discussed in a subsequent section of this lesson. The data for demand
and availability of water would be used to design the reservoir upstream of the
dam for storage. This water, when released in a regulated way, would be
diverted by a barrage and passed through a canal head regulator and water
distribution network consisting of canals and other structures such as regulators
and falls. The data requirements for construction of the structures are usually:
Topography, geology or riverbed soil characteristics, and materials.

1.4.6 Project planning for hydropower generation

A hydroelectricity generation project or a hydropower project in short, would
essentially require water diversion form a continuous surface water source like a
river. The diversion, as shown, could be using a dam or a barrage. A dam has
the advantages of creating a high head and provides sufficient storage in the
reservoir that is created behind. When the stream inflow to a reservoir is less,
the stored water may be released to generate power.

A barrage, on the other hand, does not store much water in the pool. Hence, the
power generation would be according to the available flow in the river. It also
does not create a high head and hence this type of arrangement is usually
practiced in the hilly areas, where a long power channel ensures sufficient head
for power generation. This is because the slope of the power channel would be
rather small compared to the general slope of land. A system with no sufficient
storage is called the run-of-the-river project.

Figure 4 shows a typical schematic diagram for a project with a dam for diverting
water to generate hydropower.

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Under some situation, a barrage may also be used to divert water through a
power channel to generate hydropower. This is shown in Figure 5.

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1.4.7 Data requirement for hydropower generation project
The following data is required for planning and designing a typical hydropower
system.

1.4.7.1 Demand of water

Power generated ‘P’ is proportional to the discharge ‘Q’ passing through the
turbine generator units and the piezometric head of water ‘H’. Also, the demand
of power varies with the time of the day (Figure 6) and some times on the days of
the week. Hence the demand of water that is required to drive the turbines would
vary too.

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However, when a hydropower plant is initially planned, the main constraint
comes from the stream flow availability. Demand, on the other hand, is not really
limited since more generation of power is always welcome. Hence, the
maximum installed capacity of a hydropower plant would be limited to the reliable
all-year-round available flow.

1.4.7.2 Availability of water

This has been discussed in a subsequent section of this lesson. The data for
demand and availability would decide the height of dam or a barrage and the size
of the appurtenant structures required for conveying water up to the power
generation unit and the corresponding exit channel. The data requirement for
construction of the structures is the same as mentioned before, that is,
Topography, Geology and Materials.

1.4.8 Project planning for flood control

Truly speaking, controlling a flood is generally not possible, but with different
combinations, it can be managed in such a way that the resulting damages are
minimized. There are several options, but broadly, these may be classified as
being structural or non-structural. Construction of a large dam across a river to
hold the incoming flood and the release of the regulated flow would fall under
structural measures. On the other hand, if the residents of the flood prone area
are warned before hand by making suitable predictions of the impending flood
using a flood forecasting technique, then it falls under a non-structural measure.

Lesson 6.2 deals with different types of flood management techniques, but
presently, the discussion is limited to the construction of dams for management
of floods, as illustrated in Figure 7.

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1.4.9 Data requirement for flood control project
Theoretically a dam constructed to reduce a flood peak should require the
maximum possible stream flow hydrograph.

However, this is neither possible to be determined exactly, nor is desirable as it

would too costly to build a huge dam. Rather, a flood of a certain probability of
occurrences (say 1 in 100 years) is estimated from past peak stream flow
records and a corresponding hydrograph constructed. This is generally used to
design the height of the dam (which determines the size of the reservoir) and the
spillway.

Hence, if a dam is used to moderate the flood of a river, then the data collection
should be aimed at that required for constructing a dam. They usually concern
topography, geology and materials. If other structural measures like
embankment are constructed, then also the above mentioned parameters
appropriate to the construction of embankment would be required to be collected.

1.4.10 Planning for other miscellaneous projects

Other major types of water resources project include those for

• Ecology restoration

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 • Industrial water supply
• Navigation

In each of the above, a certain demand of water is first estimated, for example.

• How much water is required for restoration of a marshy or aquatic

habitat and how is it spread overtime.
• How much water is required to be supplied to an industry (relatively
larger demands being required for the cooling of thermal energy
producing plants).
• How much water is required to flush out sediment from a navigable
channel or to what height the river water level should be raised to
increase the draft necessary for moving vessels.

Accordingly, a dam or a barrage and possibly a water conveying canal would be

required, to achieve the above objectives. The construction details for each of
these components have been dealt with in the lessons of Module 4. We shall
look now into the data requirement and its source.

1.4.11 Investigations for data assessment

The main structural components that are proposed for any water resource project
include the following:

• A storage structure like Dams

• A diversion structure like Barrages
• A water conveyance structure like Canals

The primary job of the water resources engineer would be to locate or site the
structure and for that the land surface elevation, or topography, is required.
Once a structure is sited (or a few alternatives sited), then the next phase would
be investigate the suitability of the foundation. Thus, geological characteristics
determination forms an important data requirement.

For demand intensive projects, where the demand is more than the supply, the
maximum possible flow that can be diverted for useful function is limited by the
stream flow availability. Hence, the water availability studies form the third set of
important data assessment

In the national level, the survey and investigation wing of the Central Water
Commission (CWC) takes up these assessment jobs for surface water projects
in concurrence with concerned state governments or central government. The
CWC monitors most of the country’s Major and Medium Projects and the

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detailed project reports (DPRs) have been prepared and submitted to concerned
authorities.

1.4.12 Topographic details

These are the elevation contour maps the area where a project is proposed to be
executed. The Survey of India has the responsibility to prepare and publish
such maps for the nation. The maps (called toposheet) in the scale of 1:50,000
have been completed for almost all regions the country. The contour interval in
these maps is 20 meters and each sheet covers 15 minutes of latitude and
longitude. Some areas have been surveyed in greater detail in the scale of
1:25000 in which the contour interval is 5 meters.

The survey of India also conducts specific surveys for particular project sites to
serve the needs of project authorities. The scale and contour interval depends
upon the nature of the terrain (country) and the purpose of the survey. The
National Remote Sensing Agency has also acquired a Lidar for precision
survey work with a topographic precision of 0.01m.

The elevation contour map of a region is useful to decide among others

• Height of storage structures (dam) and elevation of its spillway.

• Extent of inundation due to reservoir formation behind a dam.
• Amount of storage possible in the reservoir.
• Alignment of canals and their branches.

1.4.13 Geological characteristics

Usually hydraulic structures like dams or barrages for major water resources
projects are massive. Unless the foundation properties are correctly found from
geologic features and their interpretation, chances of structural failure would
increase. Even for barrages, which are comparatively lighter structures, the
underlying foundation strata of the river bed needs to be properly investigated.
The Geological Survey of India has produced maps showing geological
structure of the country. However, whenever a project is planned, a detailed
geological investigation is carried out by drilling Bore Holes at required number
of places and taking a Boring Log. The Strength Parameters of the underlying
rock/soil layers are investigated by extracting cores of samples and taken to
laboratory for Strength Tests. Sometimes, In-situ Laboratory Tests are
conducted that avoids disturbing the foundation material in its original form.

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 The geological tests of the foundation material of the proposed project allow the
determination of the following major parameters.

• Base width of a dam or a barrage so that the Bearing Pressure is

within safe limits.
• Degree of protection required for prevention of seepage below the
hydraulic structure. ( grout holes for dams and sheet piles for
barrages)

4.1.14 Water availability data

Lesson 1.1 gives details about the average water availability of the country in
general for a specific project dependant on surface water sources, however more
detailed data of the amount of water availability needs to be established. In fact,
the success of a water resources project depends on how accurate has been the
estimation of the total quantity of water available and its variation with time – over
days, weeks, months and years. This would require collection of data and its
analysis by suitable methods.

Project Dependable water availability*

Irrigation 75%

Drinking water 100%

Hydro power project 90%

*n% dependable availability means that the minimum water

required for the project would be available for ‘n’ units of time (say
days or weeks, 10 day period, monthly) from within 100 equivalent
units.

Database:
For computations of water availability, the following rainfall and stream runoff
data should be collected in order of preference as given below. Daily observed
data collected for ten consecutive days is more commonly used and mentioned
here as ten-daily data

• Runoff data at the proposed site for at least 40 – 50 years.

Or

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 • Rainfall data of the catchment for 40-50 years and Runoff data for at least
5-10 years.

Or

• Rainfall data of the catchment for 40-50 years and Runoff data and
concurrent rainfall data at existing project on upstream or down stream of
the proposed site for at least 5-10 years.

Or

• Rainfall data of the catchment for 40-50 years and Runoff data concurrent
rainfall data at existing project of a nearby river for at least 5 to 10 years
provided Orographic conditions of the catchment at the work site are
similar to that of the proposed site.

4.1.15 Water availability computations

Depending on the type of data available, the water availability can be computed
from the following methods:

Direct observation method:

This method is applied when observed runoff data at the proposed site is
available for the last 50 years or so. The method has been discussed in Lesson
2.4.

Rainfall-Runoff series method:

The method consists in extending the runoff data with the help of rainfall data by
means of rainfall-runoff relationships (Lessons 2.2 and 2.3).Depending upon the
availability of rainfall and runoff data, following three cases arise

• Long term precipitation record along with a stream flow data for a few
years is available.
• Long term precipitation record is available for the catchment along with a
few years of stream flow data at a neighboring site on the same river.
• Long term precipitation record is available for the catchment rainfall-runoff
data on a nearby river.

Langbein’s log-deviation method:

This method is used when short term runoff data is available at the proposed site
along with long term runoff at a nearby gauging station.

There are other methods which are discussed in the advanced texts, as the
following:

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Mutreja, K N (1995) Applied Hydrology, Tata McGraw Hill.

4.1.16 Environmental data

Any water resources project would be affecting the environment in one way or
other. Construction of a dam or barrage may not allow free movement of fish
along the river, the ponded water behind may cause submergence of valuable
forest and even human habitation. Construction of flood protection environment
may cause water logging in the area behind the embankment unless proper
drainage is provided, thus leading to breeding of mosquitoes and other disease
carrying vectors.

It is, therefore, always mandatory to check the impact on the environment due to
construction of a water resource project. For this purpose, the relevant data on
environment and ecology has to be collected for analysis.

4.1.17 Socio-economic and demographic data

Dam and barrage projects constructed at one point on a river benefits people
downstream largely. However, the construction affects the people residing on
the upstream as the ponded water causes submergence of villages and force
people to migrate. It is pertinent, therefore, to study the effect of the project on
the people and impact on the socio-economic fabric of the region benefited or
affected by the project.

4.1.18 Data collection methods

Rainfall:
This is measured with rain gauges, which may be of Recording (Figure 8) or
Non-Recording (Figure 9) types. The specifications regarding these gauges
may be found in the following Indian Standard codes of practices:

• IS: 5225 (1998) - Specifications for non-recording rain gauges.

• IS: 4986 (2002) - Installation of non-recording rain gauges and rain
measurement
• IS: 5235 (1998) - Specifications for recording rain gauges.
• IS: 8389 (2003) - Installation and use of recording rain gauges.

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The rain gauges may be distributed within the catchment as specified in the
following IS code:

• IS: 4987 (1994) - Recommendations for establishing network of rain

gauge stations

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Stream Runoff (Discharge):
The discharge of a stream or a river at a point varies with time. Usually, the
discharge is measured by calculating the average velocity of the stream and
multiplying by the cross sectional area. Since the velocity of a stream varies
across the cross section, it is usual to divide the cross section hypothetically into
several vertical strips (Figure 10).
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Calculation of the discharge passing through each strip is then done by
multiplying the average velocity of the strip by the area of the strip (approximated
as a trapezium). The velocity is measured with a current meter (Figures 11 and
12) which dipped in the flowing water to a distance of 0.6 times the depth of
water at that point, since the velocity at this point is seen to represent the
average velocity well for most streams. There are many different types of current
meters, of which the “Price” cup-type current meter attached to a round wading
rod is illustrated in Figure 8. Discussions on the principles of measurement of
stream flow, including the types of current meters may be obtained from the
United States Bureau of Reclamation online document “Water measurement
manual” which may be found in the following web-site:

http://www.usbr.gov/pmts/hydraulics_lab/pubs/wmm/indexframe.html

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Version 2 CE IIT, Kharagpur
4.1.19 Important terms
Arithmetic increase method
In this method it is assumed that, the population increases at constant a rate.
_
Therefore, population after n decades Pn = PO + n x
Where,
PO Æ Present population.
Pn Æ Forecasted population after n decades.
_
x Æ Arithmetic mean of population increase in the known decades.
n Æ No of decades.

Geometric increase method

In this method, the decade wise percentage increase or percent growth rate is
n
⎛ r ⎞
assumed to be constant. Thus, population after n decades Pn = PO ⎜1 + ⎟
⎝ 100 ⎠
Where,
PO Æ Present population.
Pn Æ Forecasted population after n decades.
r Æ Percent of increase in population in the known decades.
n Æ No of decades.

Incremental increase method

In this method it is assumed that per decade growth rate is not constant, but is
progressively increasing or decreasing. Hence, population after n decades
_
n( n + 1) _
Pn = PO + n x + y
2
Where,
PO Æ Present population.
Pn Æ Forecasted population after n decades.
_
x Æ Average increase in the known decades.
_
y Æ Average incremental increase in known decades.
n Æ No of decades.

Hydrograph: This is a plot of the discharge of a stream versus time.

Spillway: Spillway is the sluiceway/passage that carries excess water from the
water body over a dam or any other obstructions.

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Major, Medium and Minor Projects: This is a classification of the irrigation
projects in India according to the area of land cultivated.

Toposheet: The Survey of India has published maps of the entire country in
different scales. Usually, the ones in scale 1:25,000 or 1:50,000 have the
elevation contours marked out in meters. These maps are called topography
sheets, or toposheets, in short.

Lidar: LIDAR is an acronym for Light Detection and Ranging. This instrument
can:
• Measure distance
• Measure speed
• Measure rotation
• Measure chemical composition and concentration of a remote target
where the target can be a clearly defined object, such as a vehicle, or
a diffuse object such as a smoke plume or clouds
For more information, one may visit: www.lidar.com

Bore Holes
The sub-soil investigation report will contain the data obtained from boreholes.
The report should give the recommendations about the suitable type of
foundation, allowable soil pressure and expected settlements. All relevant data
for the borehole is recorded in a boring log. Depending upon the type of soil the
purpose of boring, the following methods are used for drilling the holes.
• Auger drilling
• Wash boring
• Rotary drilling
• Percussion drilling
• Core boring

Boring Log
It is essential to give a complete and accurate record of data collected. Each
borehole should be identified by a code number. All relevant data for the
borehole is recorded in a boring log. A boring log gives the description or
classification of various strata encountered at different depths. Any additional
information that is obtained in the field, such as soil consistency, unconfined
compression strength, standard penetration test, cone penetration test, is also
indicated on the boring log. It also shows the water table. If the laboratory tests
have been conducted, the information about the index properties, compressibility,
shear strength, permeability, etc. should also be provided in this log.

Strength Parameters: These are the physical strength characteristics of soils

and the important ones are:
• Shear strength (τ)

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 • Internal angle of friction or angle of shearing resistance (Φ)
• Cohesion intercept (c)
• Effective stress (σ’)

Shear strength (τ) of a soil is its maximum resistance to shear stresses just
before the failure. Shear failure occurs of a soil mass occurs when the shear
stresses induced due to applied compressive loads exceed the shear strength of
the soil. Soils are seldom subjected to direct shear. However the shear stresses
develop when the soil is subjected to direct compression. Shear strength is the
principal engineering property which controls the stability of soil mass under
loads. It governs the bearing capacity of the soils, the stability of slopes in soils,
and the earth pressure against retaining structures.
Shear strength of a soil at a point on a particular plane was expressed by
coulomb as a linear function of normal stress an that plane, as

τ = c +σ tanφ

Where,
c = cohesion interception
φ = angle which the envelop makes with σ−axis called angle of internal
friction

Effective stress (σ’) at any point in the soil mass is equal to the total stress minus
pore water pressure. Total stress (σ) on the base of a prism is equal to the force
per unit area which is given

σ = P/A = γsat h
(σ’) = σ – u = γsat h – γw h
σ’ = (γsat – γw)h = γ’h

Strength Tests: The following tests are used to measure the shear strength of
soil.
• Direct shear test.
• Triaxial compression test
• Unconfined compression test
• Vane shear test

Direct shear test: This test is performed to determine the consolidated-

drained shear strength of a sandy to silty soil. The shear strength is one of
the most important engineering properties of a soil, because it is required
whenever a structure is dependent on the soil’s shearing resistance. The
shear strength is needed for engineering situations such as determining
the stability of slopes or cuts, finding the bearing capacity for foundations,
and calculating the pressure exerted by a soil on a retaining wall.

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 The direct shear test is one of the oldest strength tests for soils. Direct
shear device will be used to determine the shear strength of a
cohesionless soil (i.e. angle of internal friction (f)). From the plot of the
shear stress versus the horizontal displacement, the maximum shear
stress is obtained for a specific vertical confining stress. After the
experiment is run several times for various vertical-confining stresses, a
plot of the maxi mum shear stresses versus the vertical (normal) confining
stresses for each of the tests is produced. From the plot, a straight-line
approximation of the Mohr-Coulomb failure envelope curve can be drawn,
f may be determined, and, for cohesionless soils (c = 0), the shear
strength can be computed from the following equation:
S = S*Tan (f)
• Direct shear device
• Load and deformation dial gauges
• Balance

Triaxial compression test: Trial test is used for determination of shear

characteristics of all types of soils under different drainage conditions. The
test has been explained in the Indian standard code (IS: 2720-1997).

Unconfined compression test: The unconfined compression test is a

special form of a triaxial test in which the confining pressure is zero. The
test can be conducted only on clayey soils which can withstand
confinement. The test is generally performed on intact, saturated clay
specimens.

Vane Shear Test: The undrained shear strength of soft clays or rocks can
be determined in the laboratory by vane shear test. The test can also be
conducted in the field on the soil at the bottom of the borehole. The field
test can be performed even without drilling a bore hole by the direct
penetration of the vane from the ground surface.

In-situ Laboratory Tests

The strength parameters of soil or rock layers are investigated by extracting
cores of samples and taken to the laboratory for testing. Insitu laboratory tests
are conducted to avoid disturbing of foundation material. These Insitu laboratory
tests mainly include plate jack test for soils and hydro fracture test for rocks.
The hydro-fracture test is done to determine the strength of underlying strata, in
case of site where huge structures, such as dams, etc are built. In this test, water
is injected into the soil at huge pressures and checked if the soil is able to bear
the pressure and even the magnitude of fractured rock can be estimated. In the
hydro-fracture test the magnitude of the minimum principal stress is determined
and back analysis is done from monitored deformations, when suitable
excavations are made for other purposes and economical monitoring can be
used. D5607-02 gives standard test method for performing laboratory direct

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shear strength tests of rock specimens under constant normal force. The Insitu
shear test or the plate jack test for the soils is explained in IS: 2720-Part39/sec2.

Bearing Pressure
Foundations for structures are generally classified as deep and shallow. Deep
foundations generally refer to piled foundations, whereas shallow foundations
include pad foundations, raft foundations, and strip footings. The performance
and functional viability of a foundation depends on the interaction between the
structure which is supported and on the founding material. The behavior of the
soil depends on the bearing pressure and width of the foundation, hence the
bearing capacity is not simply a function of the soil, but rather is also a function of
the specific foundation arrangement. Bearing pressure is the maximum pressure
at which the supporting ground is expected to fail in shear.

Orographic: Denotes effects that are related to the presence of mountains or

high ground on, say, rainfall. Orography is the study of the physical geography of
mountains and mountain ranges.

Non- Recording and Recording rain gauges

The non-recording rain gauge that is extensively used in India is the Symon’s
gauge. It essentially consists of a circular collecting area connected to a funnel.
The rim of the collector is set in a horizontal plane at a suitable height above the
ground level. The funnel discharges the rainfall catch into a receiving vessel. The
funnel and receiving vessel are housed in a metallic container. Water contained
in the receiving vessel is measured by a suitably graduated measuring glass,
with accuracy up to 0.1mm. Recently India Meteorological Department (IMD) has
changed over to the use of fiberglass reinforced polyester raingauges, which is
an improvement over the Symon’s gauge. These come in different combinations
of collector and bottles.

Recording rain gauges produce a continuous plot against time and provide
valuable data of intensity and duration of rainfall for hydrologic analysis of
storms. Following are some of the commonly used recording rain gauges.
1. Tipping bucket type
2. Weighing bucket type
3. Natural siphon type
4. Telemetering Rain gauges.
For a detailed list of commercial rain gauges usually manufactured, one may
refer to the web-site of one of the manufacturers Nova Lynx at the following web-
site:
http://www.novalynx.com/products-rain-gauges.html

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generator (H2 in Figure 20) can be determined from the height of the generator’s stator
frame and that of the load bearing bracket.

The height of the machine hall above the top bracket of the generator depends upon the
overhead cranes hook level, corresponding crane rail level, and the clearance required
between the ceiling and the top of the crane.
The layout of an in-stream power house with a bulb turbine is shown in Figure 21.
The detailed dimensions for the any of the above power houses may be done from the
following Bureau of Indian Standard codes:
IS: 12800-1993 “Guidelines for selection of turbines, preliminary dimensioning and layout of
surface hydro-electric power houses”
Part 1: Medium and large power houses
Part 2: Pumped storage power houses
Part 3: Small, mini and micro hydroelectric power houses
5.3.5 Structural design of power house
As indicated, a hydropower generating station essentially composes of a substructure and
a superstructure, when viewed from a vertical section. In plan, each single turbo-generator
unit or a few of these units are constructed monolithically as a block with vertical joints
between two adjacent block.

Stability and analysis of forces

The stability of the entire power house largely depends upon the construction of the
substructure foundation which is in direct contact with water. Primarily, the structure has to
be checked for overturning, sliding and uplift pressures. The different expected loads for
the substructure of two types of powerhouses-instream and dam based are shown in
Figure 22(a) and (b) respectively.

For the in-stream power house, the principal force here is the upstream (head water
pressure) Hu. It is partially balanced by the downstream (tail water pressure) Hd.. Sliding is
resisted at the base by friction due to the weight of the structure (W) and the weight of
water within the power house V1 and V2 on the upstream and downstream of the two gates
considering the gates to be closed and the scroll case and draft tubes as empty. From the
bottom of the structure, the uplift pressure (u) and the net base reaction pressure from the
foundation (R) balance the vertical forces. Sliding and overturning checks for the stability of
the powerhouse may be then done according to the laws of mechanics. The corresponding
stresses calculated at the base may be checked against the safe bearing pressure of the
foundation.
For powerhouses not built as an integral part of the headworks (intake), the stability check
need not include that of sliding as there is no direct hydrostatic pressure to resist from the
upstream over a large surface area as that for in-stream power houses. The upstream
water pressure is now considered as that offered by the water within the penstock (P in
Figure 22b). Since the substructure is located below the tail water level, the foundation may
be considered saturated and the upstream and downstream pressures (Hu and Hd) may be
considered same and they cancel each other. The uplift pressure may, therefore, be
considered to be uniform throughout. The self weight of the structure (W) and the weight of
water on the downstream of the structure (V) are balanced by the base reaction pressure
(R).

Structural design and construction

The substructure concrete encasing the draft tube has to support the machinery load over
the cavities and has to transmit the same to the foundation such that the pressure at the
base remains within permissible bearing pressure of foundation. The substructure and the
frames of the power house are sometimes constructed as one single stage of concreting,
as shown in Figure 23. The substructure mass concrete portion housing the draft-tube has
to be checked for loads and streams which may be done by a three dimensional stress
analysis software package. Necessary reinforcement has to be provided according to the
analysis.
Above the substructure concrete encompassing the draft tube lies the concrete housing the
scroll case which supports the load of an annular concrete block that acts as the foundation
for the heavy generator load. Both these concrete blocks (second stage concrete shown in
Figure 23) to be analyzed for forces, static as well as dynamic, caused by the rotation and
vibration of the turbines. Reinforcements have to be provided according to the stresses
obtained from the analysis, preferably using a three dimensional stress analysis software
package. The Bureau of Indian Standards code IS: 7207-1992 “Criteria for design of
generator foundation for hydroelectric power stations” may be referred to for guidance on
the respective analysis.
The superstructure of a power house consisting the structure associated with the machine
hall of the generating units, other places for electrical and auxiliary equipment, and
structures to support cranes for servicing the turbo generators during installation and repair.
For analyzing the superstructure of a surface power station, the Bureau of Indian Standards
code IS: 4247 (Part2)-1992 “Code of practice for structural design of surface hydroelectric
power station” may be referred to for further details. For an underground power house, the
superstructure components remain much the same, except the roof and walls, which are
then taken care of by the power house cavity itself.
 Module
6
MANAGEMENT OF
WATER RESOURCES
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 LESSON
1
RIVER TRAINING AND
RIVERBANK
PROTECTION WORKS

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Instructional objectives:

1. The need for river training

2. Guide bunds for restricting the flow path of river waterway
3. Afflux bunds, approach embankments, groynes ,spurs, etc. for river waterway
control
4. The issue of riverbank failure and lateral migration of rivers
5. Different modes of bank failure
6. Techniques for bank stabilization

6.1.0 Introduction
For constructing a hydraulic structure across a river, a water resources engineer must
also consider the effect of the structure on the hydraulics of the river and the best ways
to train the river such that the structure performs satisfactorily and also there is no
significant damage to the riverine environment. For example, if a barrage is located
within a river, then its length may span from end to end of the river width or could be
smaller, if the waterway is so calculated. In the latter case, that is, when the length of a
barrage is smaller than the width of a river, then certain auxiliary structures in the form
of embankments have to be constructed as shown in Figure 1, known as River Training
Works. At times, people residing very close to the flood zones of a river may have to be
protected from the river’s fury. This is done by providing embankments along the river
sides to prevent the river water from spilling over to the inhabited areas.
In order to limit the movement of the bank of a meandering river, certain structures are
constructed on the riverbank, which are called riverbank protection works. Sometimes,
an embankment like structure, called a Groyne or a Spur, is constructed at right angles
to the riverbank and projected into the river for attracting or deflecting the flow of the
river towards or away from the riverbank.
This chapter discusses the layout and design of these River Training and Riverbank
Protection Works, which can together be termed as aspects of River Engineering. Of
course, river engineering includes much more, like dredging to keep the pathway of
ships in a river navigable, or techniques of setting up jetties for ships to berth, but they
are not discussed in this lesson.

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6.1.1 Guide bunds or banks
Alluvial rivers in flood plains spread over a very large area during floods and it would be
very costly to provide bridges or any other structure across the entire natural spread. It
is necessary to narrow down and restrict its course to flow axially through the diversion
structure. Guide bunds are provided for this purpose of guiding the river flow past the
diversion structure without causing damage to it and its approaches. They are
constructed on either or both on the upstream and downstream of the structure and on
one or both the flanks as required.

Classification of Guide Bunds

Guide bunds can be classified according to their form in plan as (i) divergent, (ii)
convergent, and (iii) parallel and according to their geometrical shape as straight and
elliptical with circular or multi-radii curved head. These are shown in Figure 2.

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In the case of divergent guide bunds, the approach embankment gets relatively less
protection under worst possible embayment and hence divergent guide bunds require a
longer length for the same degree of protection as would be provided by parallel guide
bunds. They also induce oblique flow on to the diversion structure and give rise to
tendency of shoal formation in the centre due to larger waterway between curved
heads. However, in the case of oblique approaching flow, it becomes obligatory to
provide divergent guide bunds to keep the flow active in the spans adjacent to them.
The convergent guide bunds have the disadvantage of excessive attack and heavy
scour at the head and shoaling all along the shank rendering the end bays inactive.
Parallel guide bunds with suitable curved head have been found to give uniform flow
from the head of guide bunds to the axis of the diversion structure.

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In the case of elliptical guide bunds, due to gradual change in the curvature, the flow is
found to hug the bunds all along their lengths whereas in the case of straight guide
bunds, separation of flow is found to occur after the curved head, leading to obliquity of
flow. Elliptical guide bunds have also been found to provide better control on
development and extension of meander loop towards the approach embankment.

Length of Guide Bunds

The length of the guide bund on the upstream is generally kept as 1.0 to 1.5L where L is
the width between the abutments of the diversion structure. In order to avoid heavy river
action on the guide bunds, it is desirable to limit the obliquity of flow to the river axis not
more than 300 as indicated in Figure 1. The length of the downstream guide bund is kept
as 0.25L to 0.4L.
For wide alluvial belt, the length of guide bunds is decided from two important
considerations, viz. the maximum obliquity of the current and the permissible limit to
which the main channel of the river can be allowed to flow near the approach
embankment in the event of the river developing excessive embayment behind the
training works. The radius of the worst possible loop has to be ascertained from the
data of the acute loops formed by the river during the past. Where river survey is not
available, the radius of the worst loop can be determined by dividing the radius of the
average loop worked out from the available surveys of the river by 2.5 for rivers having
a maximum discharge up to 5000 cumecs and by 2.0 for a maximum discharge above
5000 cumecs.

Curved head and tail of Guide Bunds

The upstream curved head guides the flow smoothly and axially to the diversion
structure keeping the end spans active. The radius of the curved head should be kept
as small as possible consistent with the proper functioning of the guide bund. The
downstream curved tail provides a smooth exit of flow from the structure.
From the hydraulic model tests conducted for a number of projects over the past years,
it has been found that a radius of the curved head equal to 0.4 to 0.5 times the width of
the diversion structure between the abutments usually provides satisfactory
performance. The minimum and maximum values could be 150 m and 600 m
respectively. However, the exact values are to be ascertained from model tests. The
radius of the curved tail generally ranges from 0.3 to 0.5 times the radius of the curved
head.
According to the river curvature, the angle of sweep of curved upstream head ranges
from 1200 to 1450. The angle for the curved tail usually varies from 450 to 600.
In the case of elliptical guide bunds, the elliptical curve is provided upto the quadrant of
the ellipse and is followed by multi-radii or single radius circular curve. In case of multi-
radii curved head, the larger radius adjacent to the apex of the ellipse is generally kept
as 0.3 to 0.5 times the radius of the curved head for straight guide bund with the angle
of sweep varying from 450 to 600 and the smaller radius equivalent to 0.25 times the
radius of curve head for straight guide bund with sweep angle of 300 to 400.

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Design of guide bunds
After fixing up the layout of the guide bunds in accordance with the guidelines
mentioned in the foregoing paragraphs, the details of the guide bund sections have to
be worked out. The various dimensions worked out are top width, free board, side
slopes, size of stone for pitching, thickness of pitching, filters and launching apron. The
guide lines for the same are given below.

Top width of guide bund

At the formation level, the width of the shank of guide bunds is generally kept 6 to 9 m
to permit carriage of material and vehicles for inspection. At the nose of the guide
bunds, the width is increased suitably in a bulb shape to enable the vehicles to take turn
and also for stacking reserve of stone to be dumped in places whenever the bunds are
threatened by the flow.

Free board for Guide Bund

A free board of 1 to 1.5 m above the following mentioned two water levels has to be
provided and the higher value adopted as the top level of the upstream guide bund:

(i) Highest flood level for 1 in 500 years flood

(ii) Affluxed water level in the rear portion of the guide bank calculated after
adding velocity head to HFL corresponding to the design flood (1in 100 year frequency)
at the upstream nose of the guide bank.
On the downstream side also, a free board of 1 to 1.5 m above the highest flood level
for 1 in 500 years flood is to be adopted.

Side slopes of guide bund

The side slopes of guide bund have to be fixed from stability considerations of the bund
which depend on the material of which the bund is made and also its height. Generally
the side slopes of the guide bund vary from 2:1 to 3:1 (H:V).

Size of stone for pitching

The sloping surface of the guide bund on the water side has to withstand erosive action
of flow. This is achieved by pitching the slope manually with stones. The size and
weight of the stones can be approximately determined from the curves given in Figure
3. It is desirable to place the stones over filters so that fines do not escape through the
interstices of the pitching. For average velocities up to 2 m/sec, burnt clay brick on edge
can be used as pitching material. For an average velocity upto 3.5 m/sec, pitching of
stone weighing from 40 to 70 kg (0.3 to 0.4 m in diameter) and for higher velocities,
cement concrete blocks of depth equal to the thickness of pitching can be used. On the
rear side, turfing of the slope is normally found to be adequate.

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Thickness of Pitching
The thickness of pitching is to be kept equal to the size of the stone for pitching
determined. However, it should not be less than 0.25m. wherever the velocities are high
for which the size of stone is greater than 0.4 m, cement concrete blocks of thickness
0.4 to 0.5 or 0.6 m may be used.

Provision of filter
It is always desirable to provide an inverted (graded) filter below the pitching stones to
avoid the finer bund materials getting out through the interstices. The thickness of the
filter may be 20 to 30 cm. Filter has to satisfy the criteria with respect to the next lower
size and with respect to the base material:

(i) For uniform grain size filter,

D50 of filter material

R50 = = 5 to 10
D50 of base material

(ii) For graded material of sub-rounded particles,

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 D50 of filter material
R50 = = 12 to 58
D50 of base material
D of filter material
R15 = 15 = 12 to 40
D15 of base material

Launching apron
Just as launching apron is provided for the main structure both on the upstream and
downstream it has to be provided for guide bunds also in the bed in continuation of the
pitching. The different aspects to be looked into are the size of the stones, depth of
scour, thickness, slope of launched apron, shape and size of launching apron.
The required size of stone for the apron can be obtained from the curves. In case of
non-availability of required size of stones, cement concrete blocks or stone sausages,
prepared with 4 mm GI wire in double knots and closely knit and securely tied, may be
used.
The scour depths to be adopted in the calculations for the launching apron would be
different along the length of the guide bund from upstream to downstream, as given in
the following table. The value of R, that is the normal depth of scour below High Flood
Level may be determined according to Lacey’s scour relations.

Location Maximum scour depth to be

adopted
Upstream curved head of Guide 2.5 R
bund
Straight reach of guide bund to 1.5 R
nose of downstream Guide bund

While calculating the scour values, the discharge corresponding to 50 to 100 years
frequency may be adopted. However, after construction and operation of the diversion
structure, the portions of the guide bund coming under attack of the river flow should be
carefully inspected and strengthened as and when necessary.

The thickness of apron of the guide bund should be about 25 to 50 percent more than
that required for the pitching. While the slope of the launched apron for calculation of
the quantity can be taken as 2:1 for loose boulders or stones, it may be taken as 1:5:1
for c.c blocks or stone sausages.

From the behaviour of the guide bunds of previously constructed diversion structures, it
has been observed that shallow and wide aprons launch evenly if the scour takes place
rapidly. If the scour is gradual, the effect of the width on the launching of apron is
marginal. Generally a width of 1.5 R has been found to be satisfactory. For the shank or
straight portions of the guide bunds, the thickness of the apron may be kept uniform at
1.5 T where T is the thickness of the stone pitching. To cover a wider area, for the
curved head, the thickness is increased from 1.5 to 2.25 T with suitable transition over a

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length of L1 equal to one fourth of the radius of the curved head and provided in the
shank portion only. On the rear side of the curved head and nose of the guide bund, the
apron should be turned and ended in a length equal to about one fourth of the
respective radius.

6.1.2 Afflux bund

Afflux bunds extend from the abutments of guide bunds (usually) or approach bunds as
the case may be. The upstream afflux bunds are connected to grounds with levels
higher than the afflux highest flood level or existing flood embankments, if any. The
downstream afflux bunds, if provided, are taken to such a length as would be necessary
to protect the canal/approach bunds from the high floods.
Afflux bunds are provided on upstream and downstream to afford flood protection to low
lying areas as a result of floods due to afflux created by the construction of
bridge/structure and to check outflanking the structure.

Layout of afflux bund

The alignment of the afflux bund on the upstream usually follows the alluvial belt edge
of the river if the edges are not far off. In case the edges are far off, it can be aligned in
alluvial belt, but it has to be ensured that the marginal embankment is aligned away
from the zone of high velocity flow. Since the rivers change their course, it is not
necessary that a particular alignment safe for a particular flow condition may be safe for
a changed river condition. Hence the alignment satisfactory and safe for a particular
flow condition (constructed initially) has to be constantly reviewed after every flood and
modified, if necessary.

Top width of afflux bund

Generally the top width of the afflux bund is kept as 6 to 9 m at formation level.

Free board for afflux bund

The top level of the afflux bund is fixed by providing free board of 1 to 1.5 m over the
affluxed highest flood level for a flood of 1 in 500 years frequency.

Slope pitching and launching apron

Generally the afflux bunds are constructed away from the main channel of the river.
Hence they are not usually subjected to strong river currents. In such cases, provision
of slope pitching and launching apron are not considered necessary. However, it is
desirable to provide a vegetal cover or turfing. In reaches where strong river currents
are likely to attack the afflux bunds, the slopes may be pitched as for the guide bunds.
A typical layout and section of afflux bund are shown in Figure 4.

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6.1.3 Approach embankment
Where the width of the river is very wide in an alluvial plain, the diversion structure is
constructed with a restricted waterway for economy as well as better flow conditions.
The un-bridged width of the river is blocked by means of embankments called Approach
embankments or tie bunds.

Layout of approach embankment

In case of alluvial plains, the river forms either a single loop or a double loop depending
upon the distance between the guide bunds and the alluvial belt edges. Hence the
approach embankments on both the flanks should be aligned in line with the axis of the
diversion structure up to a point beyond the range of worst anticipated loop. Sometimes
the approach embankments may be only on one flank depending on the river
configuration.

Top Width of approach embankments

The top width of the approach embankment is usually kept as 6 to 9m at formation level.

Free Board of approach embankment

Free board for approach embankment may be provided similar to that for guide bunds.

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Side slopes of approach embankment
The side slopes of the approach embankment have to be fixed from stability
considerations of the bund which depend on the material of which the bund is made and
also its height. Generally the side slopes of the guide bund vary from 2:1 to 3:1 (H:V).

Size of stone for pitching

Velocities for 40 percent of the design discharge would be estimated and the size of
stone for pitching would be determined as for guide bunds discussed in Section 6.1.1.

Thickness of pitching
The Guide lines for determining the thickness of pitching would be the same as for
guide bunds in Section 6.1.1. The velocities would be estimated for 40 percent of the
design discharge.

Provision of filter
Generally filters are not provided below the pitching stones in the case of approach
embankments. However, if the section of embankment is heavy, filter may be provided
as mentioned for guide bunds discussed in Section 6.1.1.
Launching apron
The provisions of size of stone, thickness of apron and slope of launched apron would
be similar to those of guide bunds mentioned in above paragraphs. But the depth of
scour for the approach embankment may be taken as 0.5 to 1.0 Dmax and beyond that
the width may be increased to 1.0 Dmax with suitable transition in the former reach.

6.1.4 Groynes or Spurs

Groynes or spurs are constructed transverse to the river flow extending from the bank
into the river. This form of river training works perform one or more functions such as
training the river along the desired course to reduce the concentration of flow at the
point of attack, creating a slack flow for silting up the area in the vicinity and protecting
the bank by keeping the flow away from it.

Classification of Groynes or spurs

Groynes or spurs are classified according to (i) the method and materials of
construction (ii) the height of spur with respect to water level (iii) function to be
performed and (iv) special types which include the following:
These are
(i) Permeable or impermeable
(ii) Submerged or non-submerged
(iii) Attracting, deflecting repelling and sedimenting and
(iv) T-shaped (Denehey), hockey (or Burma) type, kinked type, etc.

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The different types of spurs are shown in Figure 5.

Impermeable spurs do not permit appreciable flow through them whereas permeable
ones permit restricted flow through them. Impermeable spurs may be constructed of a
core of sand or sand and gravel or soil as available in the river bed and protected on the
sides and top by a strong armour of stone pitching or concrete blocks. They are also
constructed of balli crates packed with stone inside a wire screen or rubble masonry.

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While the section has to be designed according to the materials used and the velocity of
flow the head of the spur has to have special protection.
Permeable spurs usually consist of timber stakes or piles driven for depths slightly
below the anticipated deepest scour and joined together to form a framework by other
timber pieces and the space in between filled up with brush wood or branches of trees.
The toe of the spur would be protected by a mattress of stones or other material. As the
permeable spurs slow down the current, silt deposition is induced. These spurs, being
temporary in nature, are susceptible to damage by floating debris. In bouldery or
gravelly beds, the spurs would have to be put up by weighing down timber beams at the
base by stones or concrete blocks and the other parts of the frame would then be tied to
the beams at the base.

Layout of groynes or spurs

Groynes are much more effective when constructed in series as they create a pool of
nearly still water between them which resists the current and gradually accumulates silt
forming a permanent bank line in course of time. The repelling spurs are constructed
with an inclination upstream which varies from 100 to 300 to the line normal to the bank.
In the T-shaped groynes, a greater length of the cross groyne projects upstream and a
smaller portion downstream of the main groyne.

Length of Groynes
The length of groynes depends upon the position of the original bank line and the
designed normal line of the trained river channel. In easily erodible rivers, too long
groynes are liable to damage and failure. Hence, it would be better to construct shorter
ones in the beginning and extend them gradually as silting between them proceeds.
Shorter and temporary spurs constructed between long ones are helpful in inducing silt
deposition.

Spacing of Groynes
Each groyne can protect only a certain length and so the primary factor governing the
spacing between adjacent groynes is their lengths. Generally, a spacing of 2 to 2.5
times the length of groynes at convex banks and equal to the length at concave banks
is adopted. Attempts to economise in cost by adopting wider spacings with a view to
insert intermediate groynes at a later date may not give the desired results as the
training of river would not be satisfactory and maintenance may pose problems and
extra expenditure. T-shaped groynes are generally placed 800 m apart with the T-heads
on a regular curved or straight line.

Design of groynes or spurs

The design of groynes or spurs include the fixation of top width, free board, side slopes,
size of stone for pitching, thickness of pitching, filter and launching apron.

Top width of spur

The top width of the spur is kept as 3 to 6 m at formation level.

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Free board
The top level of the spur is to be worked out by giving a free board of 1 to 1.5 m above
the highest flood level for 1 in 500 year flood or the anticipated highest flood level
upstream of the spur, whichever is more.

Side slopes
The slopes of the upstream shank and nose is generally kept not steeper than 2:1 the
downstream slope varies from 1.5 : 1 to 2:1.
Size of stone for pitching
The guide lines for determining the size of stone for pitching for guide bunds hold good
for spurs also.

Thickness of pitching
The thickness of pitching for spurs may be determined from the formula T = 0.06 Q1/3
where Q is the design discharge in cumecs. The thickness of stone need not be
provided the same through-out the entire length of the spur. It can be progressively
reduced from the nose.

Provision of filters
Provision of filter satisfying the filter criteria has to be made below the pitching at nose
and on the upstream face for a length of 30 to 4 m for the next 30 to 45m from the nose.
The thickness of the same may be 20 to 30cm. The thickness of filter for the next 30 to
45m on the upstream face may be reduced to about 15 cm and beyond that, it can be
omitted.
A typical layout of a spur is shown is Figure 6.

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6.1.5 Cut-offs
Cut-offs as river training works are to be carefully planned and executed in meandering
rivers. The cut-off is artificially induced with a pilot channel to divert the river from a
curved flow which may be endangering valuable land or property or to straighten its
approach to a work or for any other purpose. As the cut-off shortens the length of the
river, it is likely to cause disturbance of regime upstream and downstream till
readjustment is made. A pilot cut spreads out the period of readjustment and makes the
process gradual. Model tests come in handy in finalising this form of river training works
wherever needed.
A typical instance of a cutoff is shown in Figure 7.

6.1.6 Marginal embankments

These are earthen embankments, also known as levees, which are constructed in the
flood plains of a river and run parallel to the river bank along its length. The aim of
providing these embankments is to confine the river flood water within the cross section
available between the embankments. The flood water of a river is thus not allowed to
spill over to the flood plains, as normally would had been (Figure 8). This kind of
protection against flooding has been provided for most of the rivers of India that are
flood prone with low banks and have extensive flood plains in the last century. This may
be apparent from the maps of any riverine area, as shown typically in Figure 9.

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However, the ill effects of providing these embankments have become quite apparent
now, the most serious of which is the gradual rise of the river bed level over the years
due to deposition of sediments. Normally, a river in its original unrestricted shape
deposits silt along with flood water not only in its riverbed, but also on its flood plains
(Figure 10a). However, as soon a river is confined by marginal embankments, the
subsequent deposits of sediment can only take place over the river bed, thus raising the
bed elevation (Figure 10b). Instance of such phenomena has been reported for such bis
rivers like the Mississippi in the USA. In India, embanking of the Mahanadi river near
Cuttack or the Ganga near Patna or the Teesta near Talpaiguri have all caused the river
bed level to have gone up alarmingly. As a consequence, during floods, the river water
level flows alarmingly high (Figure 10c), and the residents of the nearly towns are
always under the threat of flooding.

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In view of the seriousness of this issue, marginal embankments are now being
discouraged. The flood plains rightly belong to the river, and forceful occupation of
these by artificial means like constructing embankments is harmful to the river as well
as human society itself, who had engineered the constructions.

6.1.7 Riverbank protection works

This aspect of river engineering considers methods and techniques for protecting the
banks of rivers from collapsing. Hence, certain structural interventions are required to
be implemented, which are termed as the riverbank protection works or alternately as
bank stabilization structures. Generally these are simple to construct though, the
specific hydraulic and geomorphic process associated with these structures are quite
complex and challenging. Hence, the type of bank protection work has to be in
accordance with the conditions of the specific site – a method suitable for one location
of a river may not be so far another location of the same river or at another river. For a
proper appreciation of the techniques of bank stabilization, one has to have an
awareness about fluvial geomorphology and channel processes, a brief account of
which has been discussed in Module 2.
Nevertheless, geomorphic analyses of initial morphological response to system
disturbance provides a simple qualitative method for predicting the channel response to
an altered condition. Another complicating factor in assessing the cause and effect of
system instability is that very rarely is the instability a result of a single factor. In a
watershed where numerous alterations (dams, levees, channelization, land use
changes, etc.) have occurred, the channel morphology will reflect the integration of all
these factors. Unfortunately, it is extremely difficult and often impossible to sort out the
precise contributions of each of these components to the system instability. The
interaction of these individual factors coupled with the potential for complex response
makes assessing the channel stability and recommending channel improvement
features, such as bank protection, extremely difficult. There are numerous qualitative
and quantitative procedures that are available. Regardless of the procedure used, the
designer should always recognize the limitations of the procedure, and the inherent
uncertainties with respect to predicting the behavior of complex river systems.

Local instability
Local instability is a term that refers to bank erosion that is not symptomatic of a dis-
equilibrium condition in the watershed (i.e., system instability) but results from site
specific factors and processes. Perhaps the most common form of local instability is
bank erosion along the concave bank in a meander bend which is occurring as part of
the natural meander process. Local instability does not imply that bank erosion in a
channel system is occurring at only one location or that the consequences of this
erosion are minimal. As discussed earlier, erosion can occur along the banks of a river
in dynamic equilibrium. In these instances the local erosion problems are amenable to
local protection works such as bank stabilization measures. However, local instability

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can also exist in channels where severe system instability exists. In these situations the
local erosion problems will probably be accelerated due to the system instability, and a
more comprehensive treatment plan will be necessary. Local instability of a riverbank
may be due to either streambank erosion or erosion due to meander bends. These are
explained below.

Streambank erosion and failure processes

The terms streambank erosion and streambank failure are often used to describe the
removal of bank material. Erosion generally refers to the hydraulic process where
individual soil particles at the bank’s surface are carried away by the tractive force of the
flowing water. The tractive force increases as the water velocity and depth of flow
increase. Therefore, the erosive forces are generally greater at higher flows.
Streambank failure differs from erosion in that a relatively large section of bank fails and
slides into the channel. Streambank failure is often considered to be a geotechnical
process. The important processes responsible for bank erosion are described in the
following section.

Meander Bend Erosion

Depending upon the academic training of the individual, streambank erosion may be
considered as either a hydraulic or a geotechnical process. However, in most instances
the bank retreat is the result of the combination of both hydraulic and geotechnical
processes. The material may be removed grain by grain if the banks are non-cohesive
(sands and gravels), or in aggregates (large clumps) if the banks are composed of more
cohesive material (silts and clays). This erosion of the bed and bank material increases
the height and angle of the streambank which increases the susceptibility of the banks
to mass failure under gravity. Once mass failure occurs, the bank material will come to
rest along the bank toe. The failed bank material may be in the form of a completely
disaggregated slough deposit or as an almost intact block, depending upon the type of
bank material, the degree of root binding, and the type of failure. If the failed material is
not removed by subsequent flows, then it may increase the stability of the bank by
forming a buttress at the bank toe. This may be thought of as a natural form of toe
protection, particularly if vegetation becomes established. However, if this material is
removed by the flow, then the stability of the banks will be again reduced and the failure
process may be repeated.
As noted above, erosion in meander bends is probably the most common process
responsible for local bank retreat and, consequently, is the most frequent reason for
initiating a bank stabilization program. A key element in stabilization of an eroding
meander bend is an understanding of the location and severity of erosion in the bend,
both of which will vary with stage and plan form geometry.
As streamflow moves through a bend, the velocity (and tractive force) along the outer
bank increases. In some cases, the tractive force may be twice that in a straight reach
just upstream or downstream of the bend. Consequently, erosion in bends is generally
much greater than in straighter reaches. The tractive force is also greater in bends with
short radius than those with larger ones. The severity of bank erosion also changes with
stage. At low flows, the main thread of current tends to follow the concave bank

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alignment. However, as flow increases, the streamlines tend to cut across the convex
bar to be concentrated against the concave bank below the apex of the bend. Because
of this process, meanders tend to move downstream, and the zone of maximum erosion
is usually in the downstream portion of the bend level due to the flow impingement at
the higher flows.

6.1.8 Erosional forces for bank failure

It is not quite easy to identify the processes responsible for the bank erosion. In this
section, the primary causes of bank erosion are described briefly.

Parallel flow erosion is the detachment and removal of intact grains or aggregates of
grains from the bank face by flow along the bank. Evidence includes: observation of
high flow velocities close to the bank; near bank scouring of the bed; under-cutting of
the toe/lower bank relative to the bank top; a fresh, ragged appearance to the bank
face; absence of surficial bank vegetation.

Impinging flow erosion is detachment and removal of grains or aggregates of grains by

flow attacking the bank at a steep angle to the long-stream direction. Impinging flow
occurs in braided channels where braid-bars direct the flow strongly against the bank, in
tight meander bends where the radius of curvature of the outer bank is less than that of
the channel centerline, and at other locations where an in-stream obstruction deflects
and disrupts the orderly flow of water. Evidence includes: observation of high flow
velocities approaching the bank at an acute angle to the bank; near-bank scouring of
the bed; under-cutting of the toe/lower bank relative to the bank top; a fresh, ragged
appearance to the bank face; absence of surficial bank vegetation.

Piping is caused by groundwater seeping out of the bank face. Grains are detached
and entrained by the seepage flow (also termed sapping) and may be transported away
from the bank face by surface runoff generated by the seepage, if there is sufficient
volume of flow. Piping is especially likely in high banks backed by the valley side, a
terrace, or some other high ground. In these locations the high head of water can cause
large seepage pressures to occur. Evidence includes: Pronounced seep lines,
especially along sand layers or lenses in the bank; pipe shaped cavities in the bank;
notches in the bank associated with seepage zones and layers; run-out deposits of
eroded material on the lower bank.

Freeze/thaw is caused by sub-zero temperatures which promote freezing of the bank

material. Ice wedging cleaves apart blocks of soil. Needle-ice formation loosens and
detaches grains and cleaves apart blocks of soil. Needle-ice formation loosens and
detaches grains and crumbs at the bank face. Freeze/thaw activity seriously weakens
the bank and increases its erodibility. Evidence includes: periods of below freezing
temperatures in the river valley; a loose, crumbling surface layer of soil on the bank;

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loosened crumbs accumulated at the foot of the bank after a frost event; jumbled blocks
of loosened bank material.

Sheet erosion is the removal of a surface layer of soil by non-channelized surface run-
off. It results from surface water draining over the bank edge, especially where the
riparian and bank vegetation has been destroyed by encroachment of human activities.
Evidence includes: Surface water drainage down the bank; lack of vegetation cover,
fresh appearance to the soil surface; eroded debris accumulated on the lower bank/toe
area.

Rilling and gullying occurs when there is sufficient uncontrolled surface run-off over
the bank to utilize channelized erosion. This is especially likely where flood plain
drainage has been concentrated (often unintentionally) by human activity. Typical
locations might be near buildings and parking lots, stock access points and along
stream-side paths. Evidence includes: a corrugated appearance to the bank surface
due to closely spaced rills; larger gullied channels incised into the bank face; headward
erosion of small tributary gullies into the flood plain surface; and eroded material
accumulated on the lower bank/toe in the form of alluvial cones and fans.

Wind waves cause velocity and shear stresses to increase and generate rapid water
level fluctuations at the bank. They cause measurable erosion only on large rivers with
long fetches which allow the build up of significant waves. Evidence includes: a large
channel width or a long, straight channel with an acute angle between eroding bank and
longstream direction; a wave-cut notch just above normal low water plane; a wave-cut
platform of run-up beach around normal low-water plane.

Vessel forces can generate bank erosion in a number of ways. The most obvious way
is through the generation of surface waves at the bow and stern which run up against
the bank in a similar fashion to wind waves. In the case of large vessels and/or high
speeds these waves may be very damaging. If the size of the vessel is large compared
to the dimensions of the channel hydrodynamic effects produce surges and drawdown
in the flow. These rapid changes in water level can loosen and erode material on the
banks through generating rapid pore water pressure fluctuations. If the vessels are
relatively close to the bank, propeller wash can erode material and re-suspend
sediments on the bank below the water surface. Finally, mooring vessels along the bank
may involve mechanical damage by the hull. Evidence includes: use of river for
navigation; large vessels moving close to the bank; high speeds and observation of
significant vessel-induced waves and surges; a wave-cut notch just above the normal
low-water plane; a wave-cut platform or “spending” beach around normal low-water
plane.
Retreat of river bank often involves geotechnical bank failures as well as direct erosion
by the flow. Such failures are often termed as “bank sloughing” or “caving”. Examples of
different modes of geotechnical stream bank failure are explained in the next section.

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6.1.9 Different modes of bank failure
This section summarizes the different ways by which a river bank collapses by
classifying them using geotechnical terminologies.

Soil/rock fall occurs only on a steep bank where grains, grain assemblages or blocks
fall into the channel. Such failures are found on steep, eroding banks of low operational
cohesion. Soil and rock falls often occur when a stream undercuts the toe of a sand,
gravel or deeply weathered rock bank. Evidence includes: very steep banks; debris
falling into the channel; failure masses broken into small blocks; no rotation or sliding
failures.

Shallow slide is a shallow seated failure along a plane somewhat parallel to the ground
surface. Such failure are common on bank of low cohesion. Shallow slides often occur
as secondary failures are common on banks of low cohesion. Shallow slides often occur
as secondary failures following rotational slips and/or slab failures. Evidence includes:
weakly cohesive bank materials; thin slide layers relative to their area; planar failure
surface; no rotation or toppling of failure mass.

Rotational slip is the most widely recognised type of mass failure mode. A deep seated
failure along a curved surface results in bank-tilting of the failed mass toward the bank.
Such failures are common in high, strongly cohesive banks with slope angles below
about 600. Evidence includes: banks formed in cohesive soils; high, but not especially
steep, banks; deep seated, curved failures scars; back-tilting of the top of failure blocks
towards intact bank; arcuate shape to intact bank line behind failure mass.

Slab-type block failure is sliding and forward toppling of a deep seated mass into the
channel. Often there are deep tension cracks in the bank behind the failure block. Slab
failures occur in cohesive banks with steep bank angles greater than about 600. Such
banks are often the result of toe scour and under-cutting of the bank by parallel and
impinging flow erosion.
Evidence includes: cohesive bank materials; steep bank angles; deep seated failure
surface with a planar lower slope and nearly vertical upper slope; deep tension cracks
behind the bank-line; forward tilting of failure mass into channel; planner shape to intact
bank-line behind failure mass.

Cantilever failure is the collapse of an overhanging block into the channel. Such
failures occur in composite and layered banks where a strongly cohesive layer is
underlain by a less resistance one. Under-mining by flow erosion, piping, wave action
and/or pop-out failure leaves an overhang which collapses by a beam, shear or tensile
failure. Often the upper layer is held together by plant roots. Evidence includes:
composite or layered bank stratigraphy; cohesive layer underlain by less resistant layer;
under-mining; overhanging bank blocks; failed blocks on the lower bank and at the bank
toe.

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Pop-out failure results from saturation and strong seepage in the lower half of a steep,
cohesive bank. A slab of material in the lower half of the steep bank face falls out,
leaving an alcove-shaped cavity. The over-hanging roof of the alcove subsequently
collapses as a cantilever failure. Evidence includes: cohesive bank materials; steep
bank face with seepage area low in the bank; alcove shaped cavities in bank face.

Piping failure is the collapse of part of the bank due to high groundwater seepage
pressures and rates of flow. Such are an extension of the piping erosion process
described previously, to the point that there is complete loss of strength in the seepage
layer. Sections of bank disintegrate and are entrained by the seepage flow (sapping).
They may be transported away from the bank face by surface run-off generated by the
seepage, if there is sufficient volume of flow. Evidence includes: pronounced seep lines,
especially along sand layers or lenses in the bank; pipe shaped cavities in the bank;
notches in the bank associated with seepage zones; run-out deposits of eroded material
on the lower bank or beach. Note that the effects of piping failure can easily be
mistaken for those of wave vessel force erosion.

Dry granular flow describes the flow-type failure of a dry, granular bank material.
When a noncohesive bank at close to the angle of repose is undercut, increasing the
local bank angle above the friction angle. A carpet of grains rolls, slides and bounces
down the bank in a layer up to a few grains thick. Evidence includes: noncohesive bank
materials; bank angle close to the angle of repose; undercutting; toe accumulation of
loose grains in cones and fans.

Wet earth flow failure is the loss of strength of a section of bank due to saturation.
Such failures occur when water-logging of the bank increases its weight and decreases
its strength to the point that the soil flows as a highly viscous liquid. This may occur
following heavy and prolonged precipitation, snow-melt or rapid drawdown in the
channel. Evidence includes: sections of bank which have failed at very low angles;
areas of formerly flowing soil that have been preserved when the soil dried out; basal
accumulation of soil showing delta-like patterns and structures.

6.1.10 Techniques for bank stabilization

There could be two broad ways of stabilizing banks – firstly the direct methods of
protecting the slope, and secondly the indirect way by providing structures that extend
into the stream channels and redirect the flow so that hydraulic forces at the channel
boundary are reduced to a non - erosive level.
Amongst the direct methods available for bank stabilization, the following broad
categories are as follows:
• Self-adjusting armour made of stone or other materials
• Rigid armour
• Flexible mattress

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The advantages of this type protection are that armoring the surface of the bank is a
proven approach which can be precisely designed for a given situation, and which
provides immediate and effective protection against erosion. Also, existing or potential
problems from erosion by overbank drainage can be effectively addressed integrally
with the design of the streambank armor work. Disadvantages for these types of bank
protection include preparation of the bank slope is usually required, either for
geotechnical stability or to provide a smooth surface for proper placement of the armor.
This may result in high cost, environmental damage, and disturbance to adjacent
structures. The extent of earthwork associated with an armor revetment will be
especially significant if the existing channel alignment is to be modified either by
excavation or by placing fill material in the channel. The following sections describe the
three types of bank protection works.

As for the indirect methods for bank stabilization, these may be classified into the
following categories.

• Dikes - Permeable or Impermeable

• Retards - Permeable or Impermeable
• Other flow deflectors, like Bendway weirs, Iowa vanes, etc.

The advantages of this type of protection are that little or no bank preparation is
involved. This reduces costs of local environmental impacts, and simplifies land
aquisition. However, the main disadvantage is that these are not very effective where
geotechnical bank instability or erosion from overbank drainage are the main causes of
bank erosion. Further the construction of these are not very effective where
geotechnical bank instability or erosion from overbank drainage are the main causes of
bank erosion. Further, the construction of these structures induce significant changes in
flow alignment, channel geometry, roughness and other hydraulic factors, which have to
be carefully checked to find out any adverse implication of the river’s geomorphology.
Some types of indirect protection may also pose safety hazard if the stream is used for
recreation or navigation. Lastly, since indirect methods require structures to be
constructed deep into the stream channel, their construction may become practically
difficult, especially during high flows.
Details about these indirect methods of bank protection are not presented in this lesson,
but may be obtained from references such as “The WES Stream Investigation and
Streambank Stabilization Hand book”, published by the U.S. Army Engineer Waterways
Experiment Station (WES) in 1997.

6.1.11 Self-adjusting armour of stone or other material

Stone armour can be placed in four general configurations, the most common being a
“riprap blanket”. Other forms, known as “trenchfill”, “longitudinal stone toe,” and
“windrow” (referred to in some regions as “falling apron”), canbe very useful in certain
situations.
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A stone armor usually consists of “graded” stone, which is a mixture of a wide range of
stone sizes; the largest sizes resist hydraulic forces, and the smaller sizes add
interlocking support and prevent loss of bank material through gaps between larger
stones. Hand-placed stone in a smaller range of sizes is occasionally used. The various
types of stone armours are discussed below:

Riprap Blanket
Riprap (Figure 11) should be blocky in shape rather than elongated, as more nearly
cubical stones “nest” together best and are more resistant to movement. The stone
should have sharp, clean edges at the intersections of relatively flat faces. Cobbles with
rounded edges are less resistant to movement, although the drag force on a rounded
stone is less than on sharp-edged cubical stones. As graded cobble interlock is less
than that of equal-sized angular stones, the cobble mass is more likely to be eroded by
channel flow. If used, the cobbles should be placed on flatter side slopes than angular
stone and should be about 25 percent larger in diameter.

The bed material and local scour characteristics determine the design of toe protection,
which is essential for riprap revetment stability. The bank material and ground water
conditions affect the need for filters between the riprap and underlying material.
Construction quality control of both stone production and riprap placement is essential

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for successful bank protection. Riprap protection for flood-control channels and
appurtenant structures should be designed so that any flood that could reasonably be
expected to occur during the service life of the channel or structure would not cause
damage exceeding nominal maintenance. While the procedures presented herein yield
definite stone sizes, results should be used for guidance purposes and revised if
appropriate, based on experience with specific project conditions.

Trenchfill
A trenchfill revetment, shown in Figure 12, is simply a standard stone armor revetment
with a massive stone toe. It is normally constructed in an excavated trench behind the
river bank, in anticipation that the river will complete the work by eroding to the
revetment, causing the stone toe to launch down and armor the subsequent bank slope.

Material other than stone, such as broken soil-cement, has been used successfully and
may be less costly than stone, but careful design of the soil/cement mixture, and careful
monitoring of the material mixing, breaking, and placing operation is required.

Windrow
A windrow revetment (Figure 13) is simply an extreme variation of a trenchfill revetment.
A window revetment consists of rock placed on the floodplain surface landward from the
existing bankline at a pre-determined location, beyond which additional erosion is to be
prevented.

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Longitudinal stone toe
Longitudinal stone toe (Figure 14) is another form of a window revetment, with the stone
placed along the existing streambed rather than on top bank. The longitudinal stone toe
is placed with the crown well below top bank, and either against the eroding bankline or
a distance riverward of the high bank. Typical crown elevations may vary but are
commonly between 1/3 and 2/3 of the height to top bank.

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The success of longitudinal stone toe protection is based on the premise that as the toe
of the bank is stabilized, upper bank failure will continue until a stable slope is attained
and the bank is stabilized. This stability is usually assisted by the establishment of
vegetation along the bank.

Concrete blocks
These are armour revetment for bank stabilization consisting of loose concrete blocks.
Concrete blocks fastened together forms a kind of flexible mattress that is discussed in
Section 6.1.13.
A wide variety of block shapes and placement techniques can be used. Some have
evolved from engineering analyses, some from observation and empiricism, and some
from improvisation using readily available materials. Blocks designed specifically for
bank armor are commercially available. Forms for casting concrete blocks locally are
often available from distributors, and may be an economical alternative to purchasing
and transporting precast blocks.
A fabric or granular underlayment (“filter”) is often required for riverbank protection by
concrete blocks. Successful performance of the underlayment is more critical than with
a riprap armour. In areas of high turbulence or waves, displacement of one block can
lead to successive displacement of adjacent blocks. If blocks are cast on-site, delays
from inclement weather may be a problem. At sites that are subject to theft or
vandalism, blocks of an attractive size and shape may suffer serious attrition.

Sacks
Sacks as an armor material can be considered to be artificial “rocks” of uniform size and
shape. The sacks may be made of paper, burlap, or a synthetic material. The fill
material may be soil or aggregate of various types, with or without cement. Sacks can
be placed on a steeper slope than stone. Materials are often available locally. The
hydraulic roughness is low, and they form a walkable surface. The “cobblestone” effect
may be more aesthetic than some other materials. As far concrete blocks, a fabric or
granular filter is usually required.

Soil-cement blocks
Soil is mixed well with sufficient cement to provide a durable bond between soil
particles. The resulting monolith is broken into blocks of various sizes, which are used
to armor the bank. Besides the general characteristics of adjustability to bank
irregularities and self-healing properties, soil-cement blocks allow the utilization of
locally available materials. However, soil-cement blocks have a lower specific weight
than riprap, and obtaining acceptable gradation and durability are highly dependent on
closely controlled construction operations. Construction operations are adversely
affected by wet or cold weather.

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6.1.12 Rigid armour
Rigid armour is an erosion-resistant material which has little or no flexibility to conform
to bank irregularities occurring after construction. Typically, the armour is placed directly
on the bank slope in a fluid or chemically reactive state, then hardens.
The most common rigid armours are:
• Asphalt
• Concrete
• Grouted riprap (or other grouted armour material), and
• Soil-cement
The main advantages for a rigid armour are: The most common rigid armours will
withstand high velocities, have low hydraulic roughness, and prevent infiltration of water
into the channel bank. They are practically immune to vandalism, damage from debris,
corrosion, and many other destructive agents. The most common rigid armours are
easily traversed by pedestrians.
However, a rigid armour requires careful design and quality control during construction,
and unfavourable weather conditions can cause construction delays. Provision for
draining groundwater and preventing the builtup of excess positive pore water
pressures, in the form of a filter or subsurface drains, must usually be provided for
impermeable armours, which may significantly increase the cost of the project. Most
rigid armours are difficult or impossible to construct underwater, although this difficulty
can be alleviated for concrete by using one of the commercially available fabric
mattresses. Asphalt has been placed underwater in some mattresses. Rigid armour,
being inflexible, is susceptible to breaching if the bank material subsides or heaves.
Increased wave runup on a smooth rigid armour may be a concern for some projects.
Typical applications of rigid armour in the form of concrete, asphalt, or grouted riprap is
often considered for use in situations where high velocities or extreme turbulence make
adjustable armour ineffective or very expensive. Typical uses are in conjunction with
hydraulic structures or in artificial channels on steep slopes. Rigid armour may be the
preferred alternative in flood control or drainage channels where low boundary
roughness is mandatory, or in water supply channels where prevention of water loss
due to infiltration into the bank is important. It is suitable for bank slopes which must be
easily traversed by pedestrians or recreational users, if the slope is not too steep for
safety. Rigid armour is sometimes the least costly alternative, typically where adjustable
armour is not available locally, especially if a geotechnical analysis of the bank material
indicates that elaborate subsurface drainage work is not necessary.
The important types of rigid armour are discussed in the following paragraphs.

Asphalt
Asphalt mixes with a high sand content are sometimes used to retain some permeability
to relieve hydrostatic pressure. However, these mixes have been reported to become
more brittle and less permeable upon long exposure to the elements, and weathering
may result in a slow loss of thickness.

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Concrete
On slopes above water, concrete can be placed in the conventional manner with forms,
or can be pumped into fabric mattresses which serve as forms for a fine aggregate
concrete. Prefabricated slabs would assume some of the characteristics of concrete
block armour.

Grouted armour
Grouting of an armour layer with asphalt or concrete enables the armour to withstand
higher flow velocities, provides a smooth surface for pedestrian or vehicle access, and
reduces the hydraulic roughness of the armour. Grouting is also sometimes used with
gabion armours or structures to increase the resistance of the gabions to corrosion and
abrasion.

Soil-cement
Soil-cement will withstand relatively high velocities and is usually less expensive than
concrete, asphalt, and grouted riprap. It is more durable than chemical stabilization,
clay, and certainly ice, but usually somewhat less durable than concrete, asphalt, and
grouted riprap, assuming that sound design and construction procedures are followed
for all.

6.1.13 Flexible mattress

The basic concept of a flexible mattress is that material or objects which cannot resist
erosive forces separately can be fastened together or placed in a flexible container to
provide adequate resistance to erosive forces, while partially retaining the desirable
characteristics of adjustable armour, especially that of flexibility.
The most common flexible mattress materials are:
• Concrete blocks;
• Fabric; and
• Gabions.

The advantages of this type of riverbank protection work includes its flexibility to adjust
to scour or settlement and still remain in contact with the bed and bank is the most
obvious shared trait. Most mattress materials which are sold under trade names share
another advantage they are available in various configurations, thus can be applied to a
variety of situations. Flexible mattresses can be placed underwater with a relatively high
degree of confidence. If properly anchored to a geotechnically stable bank, they can be
placed on steep slopes. They can be walked upon easily, thus are suitable for slopes
used by pedestrians.
However, it must be kept in mind that mattress components are subject to deterioration
from the elements and vandalism. The damage is often within acceptable limits through,

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and, since the various types are affected differently, identification of the hazards
enables the designer to select an appropriate mattress for a given application. The
construction of some types of mattress is labour intensive, and may require skills not
commonly available. However, the labour intensive aspect may not be a disadvantage
in all cases, and may be an advantage in some cases.
Typical applications of flexible mattresses are: This compromise between adjustable
armour and rigid armour is most attractive when economical materials can be used for
the mattress. In fact, the origin of some variations can be traced directly to creative use
of local materials where no protective material of local origin was adequate to withstand
the erosive forces in a given application, and where the most suitable method was the
one which required the least amount of costly imported material, a requirement which is
often met by a flexible mattress.

Some of the common forms of flexible mattresses are explained below:

Concrete block mattress
Mattresses provide a higher degree of safety from progressive failure of the armour due
to displacement of individual blocks from hydraulic or geotechnical forces or vandalism.
Placing of mattresses is more mechanized and less labour intensive than placing
individual blocks. Precast concrete blocks can be formed into a flexible mattress in
several ways: by fastening them to engineering fabric, by fastening them together with
cable or synthetic rope, or by forming them in ingenious shapes which are then
interlocked. All of these varieties are commercially available.

Fabric Mattress
Fabric mattresses made of synthetic material and filled with concrete grout, other
cohesive mixtures, or sand are available from various manufactures. Tubular-shaped
bags are also available; these can be filled and placed either parallel to the streambank
as a bulkhead or perpendicular to the streambank as a dike, or can be used to fill scour
holes or undermined slopes. A fabric mattress is relatively easy to place, and fill
material is often available locally. Some designs have a low hydraulic roughness.

Gabion Mattress
A gabion mattress consists of a mesh container filled with cobbles or quarried stone.
Several firms market the containers and furnish technical assistance. Spacialized
equipment or accessories used on large jobs for efficiency, or on jobs requiring
underwater placement.
A form of gabion which is a hybrid between flexible mattress and adjustable armour is
the “sack” or “sausage,” which can be filled faster than mattress or box shapes, making
it suitable for use in emergency situations. However, it makes less efficient use of
material, and is less common than traditional mattress or boxes.

Vegetation (Fascine) Mattress

Wooden mattress is one of the oldest techniques of bank stabilization, even though it is
seldom used now in developed regions. The mats may be made of poles, brush, or

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lumber. The material can be fastened together by weaving, binding, cabling, clamping,
or spiking. The mattresses are sunk by ballasting with stone or other heavy materials.
Some types of mat may be so buoyant that the ballast is a significant component of the
protection, as well as a large part of the cost.

On navigable rivers during periods when current speed is slow enough that the mats
can be safely maneuvered in tow, mats with sufficient buoyancy can be safely
maneuvered in tow, mats with sufficient buoyancy can be assembled near the materials
supply point or near a source of labour, then towed to the project site.
At least one marine construction firm has adapted modern technology to the
construction of wooden mattress, while still retaining traditional skills for use where
appropriate. They have also extended new technology to the point of developing
synthetic materials for use in mattresses, in order to overcome some of the inherent
problems of wood.
The main advantage of this type of bank protection is that its main raw material, that is,
wood is usually available locally, and is a renewable resource. If inexpensive labour is
available, a wooden mattress may be the least cost alternative. Wood is relatively
durable when permanently submerged in freshwater. However, near-site availability of
material is usually required for wooden mat to be competitive with other methods.
Assembling and placing the mattresses are labour-intensive operations. Design and
construction is surprisingly complex, requiring skills which have become rarer as other
methods have become have more popular. At some instances, bamboo mattresses
have proved very effective as fascine mattress.

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 Module
6
MANAGEMENT OF
WATER RESOURCES

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 LESSON
2
DROUGHT AND FLOOD
MANAGEMENT

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Instructional objectives:
On completion of this lesson, the student shall have learnt:

1. The consequences of abnormal rainfall – drought and floods

2. Drought and flood affected regions of India
3. Definition of drought
4. Tackling drought through water management
5. Flood management measures

6.2.0 Introduction
Water is the essential ingredient of life. Unless it is in balanced quantity, any deficit or
excess, may cause physiographic imbalance. Similarly, for an entire region, too, deficit
or excess of the normal requirement of water may cause imbalance in the regions
physical, social, or economic situation. This chapter discusses the two crucial adverse
effects of water imbalance: Droughts and Floods.
Since the beginning of the existence of mankind, drought has affected human activity
throughout the world. Historical records of drought confirm the fact that it has occurred
in almost every part of the world at sometime or other. Examples galore in the history to
show that drought is the chief cause of most famines throughout the history of mankind.
Many civilisations have perished due to abnormally long persistent deficiency of rainfall.
Syrian Desert is one such example.
In India, drought is a frequent natural calamity which finds in all the great epics of the
country. One of the earliest droughts in India has been referred in ‘Vayu Purana’. In
Ramayana also, there is description of drought during the period of king Dasaratha. In
Mahabharata, there is mention of serious drought during the reign of Emperor
Mandhata of the race of Iksvakus. Written records also give evidence of occurrence of
several famines like the one which occurred about 160 years before Mahabharata war
during the reign of King Shantanu, the ruler of Hastinapur. During the reign of king
Trishanku, father of famous King Harishchandra, a famine is said to have occurred.
King Chandragupta Maurya’s reign was also witness to a serious famine.
In pre-Independence period, the large catastrophic effect of frequent droughts and
famine caught the attention of the then British rulers in the nineteenth century when a
series of famine commissions and an Irrigation Commission were setup to go into the
various aspects of the problem and to suggest suitable measures to mitigate the
distress of the people. Indian Finance Commission in 1880 has mentioned occurrences
of severe famine and drought conditions in the then north-west province and Punjab. In
1942-44, the great Bengal famine occurred.
Despite tremendous developments in almost every field, drought continues to torment
our society constantly. Even such areas which normally have sufficient precipitation to

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meet various needs of the area, are confronted with occurrences of drought of shorter
or longer duration at sometime or other. According to an estimate, about 108 million
hectare, which works out to about one-third of the total geographical area of 329 million
hectare of the country, are affected by drought. It has been estimated that number of
people living in drought prone districts is around 263 million which is more than 26
percent of the total population of the country (as estimated in the year 2000). Hence, a
major part of our country is in the grip of this natural calamity in spite of crores of rupees
being spent by the Government on drought combating measures every year. In view of
its impact on a wide spectrum of social concerns, a proper understanding and scientific
study of drought is extremely essential so that suitable and effective drought proofing
measures are formulated in order to minimize or eliminate the adverse impacts of
drought on the economy of the country.

6.2.1 Identification of drought and flood affected areas of India

Drought
Irrigation Commission of India in 1972 identified 67 districts located in 8 states and
having an area of 49.73 million hectare as drought-prone. Subsequently, the National
Commission on Agriculture in 1976 identified a few more drought districts. The drought
identification studies carried out by Central Water Commission during 1975-82
considered 99 districts for the study located in 13 states having an area of about 108
million hectares which included those identified by the above two Commissions. For the
purpose of study, a smaller unit viz., taluka, was adopted instead of district as a whole
and the number of drought affected talukas were identified as 315 out of a total of 725
talukas in the 99 districts. Thus, out of 108 million hectare, only 51.12 million hectare
spread over 74 districts can be considered as drought prone areas.
The criteria adopted for the above study was “Drought is a situation occurring in an area
when the annual rainfall is less than 75 percent of the normal in 20 percent of the years
examined. Any taluka or equivalent unit where 30 percent or more of the cultivated
areas are irrigated, is considered to have reached a stage which enables it to sustain a
reasonably stable agriculture and to be reasonably protected against drought”.
Attempts are being made to assess as to how much area has been made drought proof
(as per the criteria of 30% or more of the cultivated area brought under irrigation with
the irrigation facilities) made available to the people. State Governments are to be
emphasised to supply this information to the concerned agencies. But it is a fact that lot
of area in the country has been converted from drought to normal since the launching of
a systematic programme of irrigation development from first Five Year Plan. Had there
been no Bhakra Dam, lot of areas of Punjab and Haryana would have been still reeling
under the severity of drought. Similarly, Indira Gandhi Nahar Pariyojana has helped in
transforming severe drought prone areas of Rajasthan to areas of abundant greenery
and general prosperity.
To cover drought prone areas, storage reservoirs have been created to supply drinking
water to far – off distant places e.g. water from Sutlej and Ravi rivers are distributed to

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dry lands of Thar desert and to villages and towns located even 500 to 800 km away
from the source, throughout the year. Otherwise the population of these villages would
have suffered due to acute water shortages.
Rabi Cultivation is a gift of storage reservoirs which supplements the production of
cereals in a big way. But for this, the country would have had to depend on import of
cereals from other countries to supplement its demand. No world market can support
the food shortages of India even of the order of 50 percent of food requirement. Self
help and natural resource generation is the only solution for sustaining the large
population.

Floods
Floods have also been a cause of misery for the country since ages. This is because,
major habitation clusters like towns and cities been located near rivers since the
beginning of civilization. Of course, for most of the cases, they were located much
above the high flood level of the river but once a while a heavy rain caused flooding of
these places as had been perhaps for Pataliputra (ancient Patna) by River Ganga or
Indraprastha (ancient Delhi) by River Yamuna.
According to the India National Commission on Irrigation and Drainage (INCID), ‘Flood’
is defined as a relatively high flow or stage in a river, marked by higher than the usual,
causing inundation of low land or a body of water, rising, swelling and overflowing land
that is not normally covered under water. Further, the damage due to flood, or Flood
Damage, may be defined as the destruction or impairment, partial or complete of the
value of floods and services or of lines resulting from the action of flood water and the
silt and debris that they carry. Flood damages arise primarily due to the occupancy of
flood plains, which rightfully belong to the river. This is because the flood plains, so to
say, are the playgrounds of a river. The flood plains are the playground of the river.
Width of these playgrounds may be roughly four to six times the waterway of dominant
discharge for meandering rivers. On the one hand, flood plains provide attractive
location for various human activities, notably agriculture and transportation such as in
Gangetic alluvial plains in U.P., Bihar, W.Bengal, Bangladesh. With increased economic
development activities, more and more of the flood plains are getting occupied.
Flood plain occupancy can be costly and in some cases may lead to disaster. Once in a
while the river may overflow its banks and exact a heavy toll of property damages,
income loss, and perhaps loss of life as well. In densely populated developing countries
of South Asia, South East Asia and China, means of sustenance are already limited and
the toll exacted by flood disasters in the flood plains is especially heavy.
The annual precipitation in India, which is the source of water causing floods, is
estimated at 4,000 BCM including snowfall. Out of this, the seasonal rainfall in monsoon
is of the order of 3,000 BCM. The flood problem in the country is mainly due to
southwest monsoon during the months from June to October. The average annual
rainfall of India is about 1170 mm, of precipitation takes place in about 15 days and less
than 100 hours altogether in a year. The rainy days may be only about five in deserts to
150 in the North East.

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The average annual flow of the rivers of India has been estimated to be about 1869
BCM. The Brahmaputra and the Ganga rivers contribute the major part of these flows.
The rivers carry major portion of their flows during the southwest monsoon period when
heavy and widespread rainfall occurs. It is mainly during this period that floods of
varying intensities are experienced in one or the other part of the country, bringing in
their wake considerable loss of life and property and disruption of communication
network.
Flooding is caused by the inadequate capacity within the banks of the rivers to contain
the high flows brought down from the upper catchment due to heavy rainfall. Areas
having poor drainage characteristics get flooded by accumulation of water from heavy
rainfall. Flooding is accentuated by erosion and silting of the river beds resulting in
reduction of carrying capacity of river channel, earthquakes and landslides leading to
changes in river courses, obstructions to flow, synchronization of floods in the main and
tributary rivers and retardation due to tidal effects. Some parts of the country mainly
coastal areas of Andhra Pradesh, Orissa, Tamil Nadu and West Bengal experiences
cyclones which often are accompanied by heavy rainfall leading to flooding. There had
been a recent case of flood due to a super cyclone combined with heavy rainfall during
October 1999 in the coastal belt of Orissa in India.

6.2.2 Characteristics of flooding in specific regions of India

The rivers in India can be broadly divided into the following four regions for a study of
flood problems:
1. Brahmaputra River Region
2. Ganga River Region
3. Northwest River Region
4. Central India and Deccan Region

The flood situation in each of these regions are described in the following paragraphs.

Brahmaputra River Region

This region consists of rivers Brahmaputra and Barak and their tributaries and covers
the States of Assam, Arunachal Pradesh, Meghalaya, Mizoram, Northern parts of West
Bengal, Manipur, Tripura and Nagaland. Catchments of these rivers receive very heavy
rainfall ranging from 110 cm to 635 cm a year which occurs mostly during the months of
May/June to September. As a result flood in this region are severe and quite frequent.
Further, the rocks of the hills, where these rivers originate, are friable and susceptible to
erosion and thereby cause exceptionally high silt charge in the rivers. In addition, the
region is subject to severe and frequent earthquakes, which cause numerous landslides
in the hills and upset the regime of the rivers. The predominant problems in this region
are the flooding caused by the spilling of rivers over the banks, drainage congestion and
tendency of some of the rivers to change their courses. In recent years, erosion along
the banks of Brahmaputra has assumed serious proportions.

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Considering the individual States in the region, main problems in Assam are inundation
caused by spilling of the Brahmaputra and the Barak and their tributaries and also
erosion along the Brahmaputra river. In northern parts of West Bengal, the Teesta,
Torsa, Jaldhaka and Mahananda are in floods every year and inundate large areas.
These rivers also carry considerable amount of silt and have a tendency to change their
courses. Rivers in Manipur spill over their banks frequently. Lakes in this territory get
filled up during monsoons and spread over large marginal areas. In Tripura, there are
problems of spilling and erosion by rivers.

Ganga River Region

River Ganga and its numerous tributaries, of which some of the important ones are
Yamuna, Sone, Ghagra, Gandak, Kosi and Mahananda, constitute this river region. It
covers the States of Uttar Pradesh, Bihar, South and central parts of West Bengal, parts
of Haryana, Himachal Pradesh, Rajasthan, Madhya Pradesh and Delhi. Normal annual
rainfall of this region varies from about 60 cm to 190 cm of which more than 80% occurs
during the southwest monsoons. Rainfall increases from west to east and from south to
north.
Flood problem is mostly confined to the areas on the northern bank of Ganga River.
Damage is caused by the northern tributaries of Ganga by spilling over their banks and
changing their courses, inundation and erosion problems are confined to a relatively few
places. In general, the flood problem increases from the west to the east and from south
to north. In the Northwestern parts of the region, there is the problem of drainage
congestion. Drainage problem also exists in the southern parts of West Bengal.
Flooding and erosion problems are serious in the States of Uttar Pradesh, Bihar and
West Bengal. In Rajasthan and Madhya Pradesh, the problem is not so serious but in
some of the recent years, these States have also experienced some incidents of heavy
floods.
In Bihar, floods are largely confined to the rivers of North Bihar and are, more or less,
an annual feature. Rivers such as Burhi Gandak, Bagmati, Kamala Balan, other smaller
rivers of the Adhwra Group, Kosi in the lower reaches and Mahananda at the eastern
end spill over their Ganga in some years causing considerable inundation of the
marginal areas in Bihar. During last few years, erosion has also been taking place along
Ganga and is now prominent on the right bank immediately downstream of the
Mokamah bridge and in the vicinity of Mansi Railway Station on the left bank.

In Uttar Pradesh, flooding is frequent in the eastern districts, mainly due to spilling of
Tapti, Sharada, Ghagra and Gandak. Problems of drainage congestion exists in the
western and northwestern areas of Uttar Pradesh, particularly in Agra, Mathura and
Meerut districts. Erosion is experienced in some places on the left bank of Ganga, on
the right bank of Gharga and on the right bank of Gandak.
In Haryana, flooding takes places in the marginal areas along the Yamuna and the
problem of poor drainage exists in some of the southwestern districts.
In south and central West Bengal, Mahananda, Bhagirathi, Ajoy, Damodar etc. cause
flooding due to inadequate capacity of river channels and tidal effect. There is also the

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problem of erosion of the banks of rivers and on the left and right banks of Ganga
upstream and downstream respectively of the Farakka barrage.
In Delhi, a small area along the banks of the Yamuna is subjected to flooding by river
spills. In addition local drainage congestion is experienced in some of the developing
colonies during heavy rains.

Northwest River Region

Main rivers in this region are the Sutlej, Beas, Ravi, Chenab and Jhelum, tributaries of
Indus, all flowing from the Himalayas. These carry substantial discharges during
monsoons and also large volumes of sediment. They changes their courses frequently
and leave behind vast tracts of sandy waste. The region covers the States of Jammu
and Kashmir, Punjab, parts of Himachal Pradesh, Haryana and Rajasthan.
Compared to Ganga and Brahmaputra River regions, flood problem is relatively less in
this region. Major problem is that of inadequate surface which causes inundation and
water logging over vast areas.
At present, the problems in the States of Haryana and Punjab are mostly of drainage
congestion and water logging. Floods in parts of Rajasthan were rare in the past.
Ghaggar River used to disappear in the sand dunes of Rajasthan after flowing through
Punjab and Haryana. In recent years, it has become active in Rajasthan territory,
occasionally submerging large areas.
Jhelum, floods occur periodically in Kashmir causing rise in the level of the Wullar Lake
there by submerging marginal areas of the lake.

Central India and Deccan Region

Important rivers in this region are Narmada, Tapi, Mahanadi, Godavari, Krishna and
Cauvery. These rivers have mostly well defined stable courses. They have adequate
capacity within the natural banks to carry the flood discharge except in the delta area.
The lower reaches of the important rivers on the east coast have been embanked, thus
largely eliminating the flood problem.
This region covers all the southern States, namely Andhra Pradesh, Karnataka, Tamil
Nadu and Kerala and the States of Orissa, Maharashtra, Gujarat and parts of Madhya
Pradesh. The region does not have serious problem except for some of the rivers of
Orissa state, namely Brahmani, Baitarni, and Subernarekha. The delta areas of
Mahanadi, Godavari and Krishna rivers on the east coast periodically face flood and
drainage problems in the wake of cyclonic storms.
Tapi and Narmada are occasionally in high floods affecting areas in the lower reaches
in Gujarat.
The flood problem in Andhra Pradesh is confined to spilling by the smaller rivers and
submergence of marginal areas along the Kolleru Lake. In addition, there is a drainage
problem in the deltaic tracts of the coastal districts.
In Orissa, damage due to floods is caused by Mahanadi, Brahmani and Baitarni which
have a common delta where the floodwaters intermingle and when in spate
simultaneously cause considerable havoc. The problem is accentuate when the flood

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synchronizes with high tides. Silt deposited constantly by these rivers in the delta area
raises the flood level and the rivers often over-flow their banks or break through new
channels causing heavy damage. Lower reaches of Subernarekha are affected by
floods and drainage congestion. Small rivers of Kerala when in high floods cause
considerable damage occasionally.
Details of annual damage due to floods in any one of the years under consideration is
taken as the area liable to flood in that State. Considering all such figures for all the
States for the period from 1953 to 1978, Rashtriya Barh Ayog (National Commission on
Floods) has assessed the total area liable to flood in the country as 40 m.ha. out of
which 32m.ha area could be provided with reasonable degree of protection. The
severity of the problem can be seen from the fact that this area constitutes one eighth of
total geographical area of the country.

6.2.3 The concept of drought

Drought has many definitions, but mostly it originates from a deficiency of precipitation
over an extended period of time, usually a season or more. This deficiency results in a
water shortage for some activity, group, or environmental sector. Drought should be
considered relative to some long term average condition of balance between
precipitation and evapotranspiration (i.e., evaporation+transpiration) in a particular area,
a condition often perceived as “normal”. It is also related to the timing (i.e., principal
season of occurrence, delays in the start of the rainy season, occurrence of rains in
relation to principal crop growth stages) and the effectiveness (i.e., rainfall intensity,
number of rainfall events) of the rains. Other climatic factors such as high temperature,
high wind, and low relative humidity are often associated with it in many regions of the
world and can significantly aggravate its severity. There are four disciplinary definitions
of drought, which are as follows:

Meteorological Drought
Meteorological drought is defined usually on the basis of the degree of dryness (in
comparison to some “normal” or average amount) and the duration of the dry period.
Definitions of meteorological drought must be considered as region specific since the
atmospheric conditions that result in deficiencies of precipitation are highly variable from
region to region. For example, some definitions of meteorological drought identify
periods of drought on the basis of the number of days with precipitation less than some
specified threshold.

Agricultural Drought
Agricultural drought links various characteristics of meteorological (or hydrological)
drought to agricultural impacts. Focusing on precipitation shortages, differences
between actual and potential evapotranspiration. Soil water deficits, reduced ground
water or reservoir levels, and so forth. Plant water demand depends on prevailing
weather conditions, biological characteristics of the specific plant, its stage of growth,
and the physical and biological properties of the soil. A good definition of agricultural

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drought should be able to account for the variable susceptibility of crops during different
stages of crop development, from emergence to maturity. Deficient topsoil moisture at
planting may hinder germination, leading to low plant populations per hectare and a
reduction of final yield. However, if topsoil moisture is sufficient for early growth
requirements, deficiencies in subsoil moisture at this early stage may not affect final
yield if subsoil moisture is replenished as the growing season progresses or if rainfall
meets plant water needs.

Hydrological Drought
Hydrological drought is associated with the effects of periods of precipitation (including
snowfall) shortfalls on surface or subsurface water supply (i.e., streamflow, reservoir
and lake levels, ground water). The frequency and severity of hydrological drought is
often defined on a watershed or river basin scale. Although all droughts originate with a
deficiency of precipitation, hydrologists are more concerned with how this deficiency
plays out through the hydrologic system. Hydrological droughts are usually out of phase
with or lag the occurrence of meteorological and agricultural droughts. It takes longer for
precipitation deficiencies to show up in components of the hydrological system such as
soil moisture, streamflow, and ground water and reservoir levels. As a result, these
impacts are out of phase with impacts in other economic sectors.

Socioeconomic Drought
Socioeconomic definitions of drought associate the supply and demand of some
economic good with elements of meteorological, hydrological, and agricultural drought.
It differs from the aforementioned types of drought because its occurrence depends on
the time and space processes of supply a demand to identify or classify droughts. The
supply of many economic goods, such as water, forage, food grains, fish, and
hydroelectric power, depends on weather. Because of the natural variability of climate,
water supply is ample in some years but unable to meet human and environmental
needs in other years. Socioeconomic drought occurs when the demand for an economic
goods exceeds supply as a result of a weather-related shortfall in water supply.
The sequence of impacts associated with meteorological, agricultural, and hydrological
drought further emphasizes their differences. When drought begins, the agricultural
sector is usually the first to be affected because of its heavy dependence on stored soil
water. Soil water can be rapidly depleted during extended dry periods. If precipitation
deficiencies continue, then people dependent on other sources of water will begin to
feel the effects of the shortage.

6.2.4 Indices for drought monitoring

Drought indices are numbers on a certain scale, which defines drought quantitatively.
The most commonly used indices world wide, which are based on a number of data on
rainfall, snowpack, streamflow, and other water supply indicators, are discussed in the
following paragraphs.

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Percent of normal
Percent of normal precipitation is one of the simplest measurements of rainfall for a
location. Analyses using the percent of normal are very effective when used for a single
region or a single season. Percent of normal is also easily misunderstood and gives
different indications of conditions, depending on the location and season. It is calculated
by dividing actual precipitation by normal precipitation-typically considered to be a 30
scales range from a single month to a group of months representing a particular
season, to an annual or water year. Normal precipitation for a specific location is
considered to be 100 percent.
One of the disadvantages of using the percent of normal precipitation is that the mean,
or average precipitation is often not the same as the median precipitation, which is the
value exceeded by 50 percent of the precipitation occurrences in a long-term climate
record. The reason for this is that precipitation on monthly or seasonal scales does not
have a normal distribution. Use of the percent of normal comparison implies a normal
distribution where the mean and median are considered to be the same.

Standardized Precipitation Index (SPI)

The understanding that a deficit of precipitation has different impacts on groundwater,

reservoir storage, soil moisture, snowpack, and streamflow led scientists to develop the
Standardized Precipitation Index (SPI). The SPI was designed to quantify the
precipitation deficit for multiple time scales. These time scales reflect the impact of
drought on the availability of the different water resources. Soil moisture conditions
respond to precipitation anomalies on a relatively short scale. Groundwater, streamflow,
and reservoir storage reflect the longer-term precipitation anomalies.
The SPI calculation for any location is based on the long-term precipitation record for a
desired period. This long-term record is fitted to a probability distribution, which is then
transformed into a normal distribution so that the mean SPI for the location and desired
period is zero. Positive SPI values indicate greater than median precipitation, and
negative values indicate less than median precipitation. Because the SPI is normalized,
wetter and drier climates can be represented in the same way, and wet periods can also
be monitored using the SPI.

Palmer Drought Severity Index (PDSI)

The PDSI is a meteorological drought index, and it responds to weather conditions that
have been abnormally dry to abnormally wet. When conditions change from dry to
normal or wet, for example, the drought measured by the PDSI ends without taking into
account streamflow, lake and reservoir levels, and other longer-term hydrologic impacts.
The PDSI is calculated based on precipitation and temperature data, as well as the local
Available Water Content (AWC) of the soil. From the inputs, all the basic terms of the
water balance equation can be determined, including evapotranspiration, soil recharge,
runoff, and moisture loss from the surface layer. Human impacts on the water balance,
such as irrigation, are not considered. The classification of a region according to this
index is as follows:

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 4.0 or more Extremely wet
3.0 to 3.99 Very wet
2.0 to 2.99 Moderately wet
1.0 to 1.99 Slightly wet
0.5 to 0.99 Incipient wet spell
0.49 to -0.49 Near normal

Crop Moisture Index (CMI)

The Crop Moisture Index (CMI) uses a meteorological approach to monitor week-to-
week crop conditions. It was developed from procedures within the calculation of the
PDSI. Whereas the PDSI monitors long-term meteorological wet and dry spells, the CMI
was designed to evaluate short-term moisture conditions across major crop-producing
regions. It is based on the mean temperature and total precipitation for each week
within a climate division, as well as the CMI value from the previous week.
Because it is designed to monitor short-term moisture conditions affecting a developing
crop, the CMI is not a good long-term drought monitoring tool. The CMI’s rapid
response to changing short-term conditions may provide misleading information about
long-term conditions. For example, a beneficial rainfall during a drought may allow the
CMI value to indicate adequate moisture conditions. For example, a beneficial rainfall
during a drought may allow the CMI value to indicate adequate moisture conditions,
while the long-term drought at that location persists. Another characteristic of the CMI
that limits its use as a long-term drought monitoring tool is that the CMI typically begins
and ends each growing season near zero. This limitation prevents the CMI from being
used to monitor moisture conditions outside the general growing season, especially in
droughts that extend over several years. The CMI also may not be applicable during
seed germination at the beginning of a specific crop’s growing season.

Surface Water Supply Index (SWSI)

The objective of the SWSI was to incorporate both hydrological and climatological
features into a single index value resembling the Palmer Index for each major river
basin in the state of Colorado in U.S.A. These values would be standardized to allow
comparisons between basins. Four inputs are required within the SWSI: snowpack,
streamflow, precipitation, and reservoir storage in the winter. During the summer
months, streamflow replaces snowpack as a component within the SWSI equation.
The procedure to determine the SWSI for a particular basin is as follows: monthly data
are collected and summed for all the precipitation stations, reservoirs, and
snowpack/streamflow measuring stations over the basin. Each summed component is
normalized using a frequency analysis gathered from a long-term data set. The
probability of non-exceedence (the probability that subsequent sums of that component
will not be greater than the current sum) is determined for each component based on
the frequency analysis. This allows comparisons of the probabilities to be made
between the components. Each component has a weight assigned to it depending on its
typical contribution to the surface water within that basin, and these weighted
components are summed to determine a SWSI value representing the entire basin. Like

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the Plamer Index, the SWSI is centered on zero and has a range between -4.2 and
+4.2.

Reclamation Drought Index (RDI)

Like the SWSI, the RDI is calculated at a river basin level, and it incorporates the supply
components of precipitation, snowpack, streamflow, and reservoir levels. The RDI
differs from the SWSI in that it builds a temperature-based demand component and a
duration into the index. The RDI is adaptable to each particular region and its main
strength is its ability to account for both climate and water supply factors.

Deciles
Arranging monthly precipitation data into deciles is another drought-monitoring
technique. It was developed to avoid some of the weakness within the “percent of
normal” approach. The technique they developed divided the distribution of occurrences
over a long-term precipitation record into tenths of the distribution. They called each of
these categories a decile. The first decile is the rainfall amount not exceeded by the
lowest 10% of the precipitation occurrences. The second decile is the precipitation
amount not exceeded by the lowest 20% of occurrences. These deciles continue until
the rainfall amount identified by the tenth decile is the largest precipitation amount within
the long-term record. By definition, the fifth decile is the median, and it is the
precipitation amount not exceeded by 50% of the occurrences over the period of record.
The classification of a region according to deciles is as follows:

Deciles 1-2: Much below normal

lowest 20%
Deciles 3-4: Below normal
next lowest 20%
Deciles 5-6: Near normal
middle 20%
Deciles 7-8: Above normal
next highest
Deciles 9-10: Much above normal
highest

6.2.5 Tackling drought through water management

Mean annual rainfall over the country is around 119 centimeters, out of which about 80
percent rainfall occurs only during the 4 monsoon months of the year. However, this
rainfall varies widely from region to region, season to season and year to year. While
some of the regions of the country receive as much as 10,000 millimetres (mm) or more
like the hills of Assam, a major part of Rajasthan gets only 100mm or even less. Low
rainfall leads to arid conditions which persist almost throughout the year. Nearly 9
percent area of the country is arid and 40% is semi-arid (annual rainfall between 500

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and 1000 mm). Because of large variability of rainfall both in space and time, semi-arid
regions are subjected to the problems of drought. The problems of arid areas wherever
one good crop is not possible in normal years is quite different from those of semi-arid
areas where one good crop is normally expected but it is frequently lost due to scanty
rainfall or due to variability of rainfall. Even normally high rainfall areas face failure of
rains and consequent upsetting of human water requirements. Water conservation and
water management measures are need of the day to achieve a strong and stable
economic base, especially in the arid and drought prone areas of the country. There are
no general solutions possible. They will have to be area specific, because of the
hydrological peculiarities. It has also to be remembered that development of drought
prone areas cannot be modelled on the lines of the development of other favourably
placed areas. The pattern of development of the drought-prone areas will have to be
quite different from that of the others.
Some of the methods that may be suggested as technical strategies to mitigate the
adversities of drought are mentioned in the following paragraphs.

Creation of surface storage

Conventional approach to water conservation has been to go in for water development
projects – creating reservoirs by building dams, big and small, and diversion canals – to
supply water wherever and in whatever amounts desired. The total storage capacity of
all the reservoirs (major, medium and minor) in the country has been assessed as 400
cubic kilometer. Central Water Commission is regularly monitoring the storage
availability of 70 selected major and medium reservoirs with a storage capacity of about
131 cubic kilometer, out of which reservoirs with storage capacity of about 50 cubic
kilometer are located in the drought prone areas. Comparing this with the overall
utilisable potential of 690 cubic kilometer of surface water apparently shows that to
overcome our water supply problems, we have to go in for creation of more storages.
However, this will not solve the main problems raised due to large spatial and temporal
variations in rainfall. One is that the overall figure of availability of water resources
presents a misleading picture. In some regions there is scope of storage but so much of
water is not needed. Many river basins like Cauvery, Sabarmati have already exhausted
the available water resources. In many other basins, water is fast becoming scarce. The
second problem is that building dams and canals has become an extremely costly
proposition. This is partly due to the increase in the basic cost of construction and partly
due to the necessity to tackle more complex projects involving difficult foundations etc.

Planning for less dependable yield

In India normally the drinking water supplies are planned for almost 100 percent
dependability, hydro-power systems for 90 percent dependability and the irrigation
systems for 75 percent dependability. However, for the drought areas, planning of
average flows or 50 percent dependability has been recommended by many
Commission and Committees to increase the availability of water mainly for the
agricultural purposes. Minor irrigation tanks (i.e. which have culturable command area
of 2,000 hectare or less) are already being planned for 50 percent dependability.

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Prevention of evaporation losses from reservoirs
It is seen that shallow tanks having large surface areas located in the drought affected
areas lose nearly half the water storage by evaporation in summer months. To save
water in a critically water short region, an application of a layer of chemicals like cetyl,
stearyl and fatty alcohol emulsions can effectively retard evaporation and savings in the
field can be around 40 percent of the normal evaporation losses.

Adjustment in sanctioned water to a reservoir or its releases

The trend of reservoir filling or the ground water position for a water year gets fairly
known by the middle of August. Re-adjustment of sanctions and releases have to be
carefully carried out at this time keeping a close watch on the behaviour of the
monsoon. The modern management techniques using probability analysis may help in
assessing the situations of ‘supply-variability’ in the drought areas.

Reduction in conveyance losses

Reduction in conveyance losses in the conveyance system is an important facet of the
water conservation techniques because losses due to seepage are found to vary widely
in an irrigation system ranging from 35 percent to 45 percent of the diverted water.
Lining of the canal system could be an appropriate step to conserve this precise
resource in such a situation.
Considering the high degree of losses in dry summer months, running a canal system in
the drought areas during the hot dry months will not be an economical proposition. As
an alternative, it will be better to transport as much water during the wet monsoon
months or later during the winter period thereafter and to store water in small tanks or
ponds near the point of consumption for later use during the summer months. Similarly,
practice usually adopted for releasing water through the river channel itself for
transporting over long distances during the dry months should be discouraged.
However, in cases where releases have to be made during summer months through the
river channel instead of resorting to releasing continuous low flows over long periods it
would be better to rush the requisite quantity in a small period and then hold it up in
small storages near the points of consumption. Such rush systems are being
successfully practiced in Maharashtra.

Equitable distribution
Many of the existing canal systems are not able to supply an adequate and equitable
quantum of water to all the farmers in the command areas. A rotational system of supply
of water if strictly implemented will not only meet the ends of equity but will also
economise use of water. Lack of adequate control arrangements in the canal systems
also adds to the problem of equitable distribution of water. Another important aspect of
water management is the prevention of loss of water to drains during transit from outlet
to field. This can be eliminated by farmers active participation in water distribution and
maintenance of distribution network in good shape.

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Maintenance of irrigation systems
Over the years, maintenance of irrigation systems has deteriorated mainly due to the
fact that water rates charged are not sufficient for carrying out the maintenance for
keeping the system fit and efficient. In some States, leave alone the operation and
maintenance, the revenue collected from irrigation rates does not even cover the
expenses incurred on collection of revenue. Whole range of activities covering
operation, routine maintenance, special and major repairs, replacements etc. are now
covered under “ maintenance” and funds are allocated to it from non-plan. Due to
shortages of funds and restrictions on non-plan activities, most of the allotted money
under this is being spent on staff salaries. Unless adequate allocations are earmarked
for maintenance of irrigation systems, gradual deterioration of the existing irrigation
systems cannot be controlled.

Better irrigation practice

On farm irrigation practices prevailing in the country also result in wastage of water
leading to poor irrigation efficiency. Most farmers still irrigate as their predecessors did
hundreds of years ago by flooding or channeling water through parallel furrows.
Absence of field channels for adopting to field irrigation adds to the problem. Simple
measures like leveling of the fields so that water gets more evenly distributed can
greatly improve the performance. Wastage due to absence of field channels and lack of
field leveling are now being eliminated through the Command Area Development (CAD)
programmes.

Irrigation scheduling
Better irrigation scheduling practices can also improve the irrigation efficiency. For
example, it is now well established that water is required more at critical stages of crop
growth and water stress during other period has negligible impact on yields. Addition
waterings do not add proportionately more to the yield. Greater effort should be made to
train farmers in the use of irrigation scheduling methods appropriate to their mode of
production. Agricultural extension programmes could help spread the benefits of these
water management techniques.

Cropping pattern
Better water management involves all stages i.e. from pre-project formulation to
operation and maintenance. In the project formulation stage, a suitable cropping pattern
in conformity with soil and climatic conditions taking into account the farmers
preferences should be evolved. While designing the canal capacities, peak demand of
water in critical periods by the high yielding varieties of crops should be kept in view.

Conjunctive use of surface and ground water

The concept of conjunctive use of surface and ground water resources is very essential
especially in drought areas in order to increase the production per unit of water. The
manner of using ground water and surface water varies considerably from region to
region. Where ground water quality is not good, canal water can be mixed in suitable
proportion. Conjunctive use makes possible same flexible of cropping pattern and multi-

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cropping in the canal command. For the proper water management, it is necessary to
treat command areas as one composite unit and two resources should be judiciously
managed to achieve optimization of benefits. Costs of exploiting the two sources vary
considerably and efforts are necessary to lay uniform charges for providing irrigation to
serve the area in an optimal manner and to achieve maximum food production. The
concept of conjunctive use has been successfully implemented in various States.
Conjunctive use of surface and ground water supplies needs careful planning on more
scientific lines to achieve full benefits particularly in all drought management
programmes. Suitable legislation is called for to regulate over-exploitation of ground
water, which at present is developed and used on individual ownership basis.

Watershed development
Planning of watershed development involves an integrated approach upon
physiographic and hydrologic characteristics which include construction of soil
conservation works on crop lands; Construction of structures, like check dams, Nalla
bunding, contour bunds, Gully plugging, percolation tanks, development of rainwater
harvesting and construction of wells etc.
Ministry of Agriculture’s proposal of National Watershed Development Projects focuses
on aspects from the angle of agriculture environment, forests and rural development
and heavy investment is envisaged for macro level development. Pilot projects for
Watershed Development in Rainfed areas in Andhra Pradesh, Karnataka, Madhya
Pradesh and Maharashtra have already been implemented with World Bank assistance.
This is a long term development, whereas watershed development at micro level will
lead to quick results in increasing the water availability and leading to sustainable
development. Presently, there are several externally aided projects sponsored by the
Central Government and funded by the World Bank and other Organisations which are
going on in various parts of the country. Some State Governments namely Andhra
Pradesh, Karnataka, Madhya Pradesh, Maharashtra, Orissa and Rajasthan have also
started watershed development programmes on their own, with some success as at
Jhabua in Madhya Pradesh. In this connection, it is worth mentioning that watershed
development in drought prone areas needs involvement of both Government and Non-
Government agencies using Non-Government Organisations (NGOs) as an interface
between the Government and the local village communities for revival, restoration and
development of the watersheds. Examples of Ralegaon-Shindi, Adgaon, Rendhar,
Sukhomajri, Tejpura, Nalgaon, Daltonganj, Sidhi, Jawaja and Alwar show that Voluntary
organizations and Non-Government Organisations can play a major role in the
watershed development and management.

Creation of large storages

While planning various projects particularly in the regions depending on rainfall, it is
preferable to go in for large storages rather than a large number of small storages on
the tributaries, since small tanks are particularly vulnerable to drought. This is also
essential in view of the fact that about 80 percent of the river flow occurs only during the
four monsoon months and this flow requires to be stored for irrigation and power
generation. The present storage capacity of all the reservoirs including major, medium
and minor schemes is 400 cubic kilometer as against the potential of 690 cubic

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kilometre which means the water scarcity problem may be solved to a great extent by
creation of more storages.

Integrating small reservoirs with major reservoirs

Of late, there are persistent demands to abandon the schemes of large storages as it is
feared that they cause environmental disaster leading to non-sustainable development
of water resources. Instead, number of small reservoirs are being advocated to replace
a single large reservoir. However, in many cases, a group of small schemes may not
provide the same benefits as a large project can. It is, therefore, very important that
minor schemes are integrated with the canal systems of major reservoirs.

Transfer of water from water excess basins to water-deficit basins

A permanent long term solution to drought problem may be found in the basic principles
of transfer of water from surplus river basins to areas of deficit. For this purpose, it is
essential to take an overall national view for the optimum utilisation of available water
resources. With this aim in view, Ministry of Water Resources and Central Water
Commission have formulated a national perspective plan for water resources
development which consists of two components: Himalayan Rivers Development and
Peninsular Rivers Development.
The national perspective of water resources development envisages construction of
about 185 cubic kilometre of storages. These storages and the interlinks will enable
additional utilisation of nearly 210 cubic kilometre of water for beneficial uses, enabling
irrigation over an additional area of 35 million hectare, generation of 34 million kilowatts
of hydro power and other multi-purpose benefits.
In order to give concrete shape to these proposals, Government of India has set up
National Water Development Agency in 1982 which is carrying out
prefeasibility/feasibility level studies of linking of various rivers both in Peninsular as well
as Himalayan Rivers Development Components based on internationally accepted
norms.

6.2.6 Flood protection measures in India over the years

In India, flood protection measures using embankments were in existence for centuries.
This is evident from the old embankments constructed by private individuals for the
protection of their lands.
The inadequacy of the individual efforts in the sphere of flood control led to
governmental interest in the problem chiefly during the past century. As a result of this,
a number of well-planned embankments were constructed on some of the rivers, which
were causing recurrent flood damage. These measures were largely to give protection
to the commanded areas of the canal systems in northern India, and the deltaic tracts of
east flowing rivers in Orissa, Andhra Pradesh and Tamil Nadu.

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In the fifties, the Damodar Valley Dams, viz., Tilaiya Dam (1953), Maithon Dam (1957)
and Panchet Dam (1959) were constructed for multipurpose development of Damodar
Valley, which included flood control also. A barrage at Durgapur downstream of the
Maithon and Panchet Dams and an upstream dam at Tenughat were also constructed
and are operating as a unified system for flood control apart from other major purposes
of irrigation, power generation and water supply requirements. The system has helped
to moderate the intensity of the floods in the lower valley considerably and the Damodar
is no longer, a ‘river of sorrow’ of the pre-project era.
Kosi Flood Control Schemes (1959) have certainly helped in checking the movement of
the river in westward direction and provided better protection to a large area of about
2.5 lakh hectares which used to be ravaged by floods. Large-scale economic
development has come up in this area.
Similarly, storage reservoirs such as Hirakud, Ukai, Bhakra, Beas, Chambal Dam and
Nagarjunsagar have either protected some areas from floods or have reduced their
intensity considerably. In addition to these, Baigal reservoir in Uttar Pradesh, Rengali
Dam and Bhimkund project in Orrisa, Multipurpose reservoirs on the Subernarekha for
the benefit of Orissa, Bihar and West Bengal, Halai Dam in Madhya Pradesh and
Mecharbali Dam in Karnataka have been useful for reduction of flood fury. The
Kangasabati Reservoir in West Bengal also takes care of flood problem in the
downstream.
A number of drainage schemes have been taken up in the States of Punjab, Haryana,
Rajasthan and Gujarat. Such schemes have also benefited the States of Uttar Pradesh
and West Bengal and water logged areas in Punjab and Haryana. The Krishna
Godavari Delta Drainage Scheme in Andhra Pradesh has also resulted in positive
developments.
Similarly, a number of schemes for channel improvements, raising of villages, anti-
erosion and town protection works have been taken up towards protection from floods.
In addition to the above for tackling the flood problem in Ganga and its tributaries and to
facilitate effective coordination of flood management among the Ganga Basin States,
Government of India set up Ganga Flood Control Board and its Secretariat, namely
Ganga Flood Control commission in April, 1972. The Ganga Flood Control Commission
has prepared comprehensive plans for flood management for all the 23 river systems of
Ganga by the year 1990. The Comprehensive Plans have been sent to State
Governments for preparing detailed schemes based on actual ground surveys and
investigations and implementation. Similarly, Government of India had set up
Brahmaputra Board under an Act of Parliament (46 of 1980) in December, 1981. The
objective of the Board is mainly to prepare a Master Plan for the control of floods and
bank erosion and improvement of drainage in the Brahmaputra and Barak Valley. The
Board has prepared Master Plans for Main Brahmaputra River (1986) and Barak Valley
(1988) and 38 tributaries. These have been also forwarded to States for taking further
action towards their implementation.
Flood management schemes are taken up by respective State Governments in their
successive plans. It is estimated that a total of 16,199 km length of embankments and
32,003 km length of drainage channels were constructed; a total of 906 towns were

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protected and 4,721 villages were provided protection from floods upto the year 1997.
From the above works, it is estimated that an area of 14.37m.ha has benefited.
The evolution of flood management policy in India can be summarized as below:

Before 1947 Main emphasis on flood embankment

1954 Policy statement in Parliament: Two document presents
“ Floods in India-problems and Remedies” and “The Floods in
the Country”
- absolute immunity from flood damage is not physically possible
even in the distant future.
1957 High level committee on floods
-Non structural measures were recommended
1964 Ministerial committee on flood control
-Non structural measures were emphasized
1972 Ministers Committee on floods and flood relief
-additional storage for flood moderation
-Legislation to prevent encroachment of river
-Restricting the costly anti erosion works to important locations
1980 Rashtriya Barh Ayog (National flood commission): A
comprehensive report
207 recommendations covering entire gamut of flood problems
CWC in 1987 reviewed implementation status of these
recommendations and found not much progress. even now (in
2005) not much progress.
1987 National water policy
-Basin master plans, watershed management catchment area
treatment
1999 National commission for integrated water resources development
-Efficient management of flood plains and other non structural
measures
-Performance of embankments to be evaluated
-Flood forecasting network to be extended

It may be mentioned here that the organizations that are responsible for the
management of flood in the country are the following.

State Flood Control Department Planning and execution of flood

management works

Central Water Commission (River Management Wing)

Coordination
and guidance

Ganga Flood Control Commission Master plans for flood control in 23

sub

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 basins of Ganga have been prepared

Ganga Flood Control Commission (1981) Survey and Investigation,

Preparation of plans for flood control
and bank erosion in Brahmaputra
and Barak Valleys.

6.2.7 Flood management initiatives

Flood management activities can be broadly classified into four major groups:
i. Attempts to modify the flood
ii. Attempts to modify the susceptibility to flood damage
iii. Attempts to modify the loss burden
iv. Bearing the loss

All these measures for flood management can be classified as under:

• Structural measures
• Non-structural measures

Broadly, all measures taken up under the activity of “Modifying the flood” which are in
the nature of physical measures are “Structural measures”, while the others which are
taken up as management tools without major construction activity are grouped as “Non-
structural measures”. These are explained in the subsequent sections.

6.2.8 Structural measures for flood mitigation

The general approach to tackle the problem of floods in the past has been in the form of
physical measures with a view to prevent the flood waters from reaching potential
damage centres. This approach had been extensively constructed in the Godavari,
Krishna and Cauvery Deltas in South India and also in some areas of Indo-Gangetic
plain.
The main thrust of the flood protection programme undertaken in India so far has been
in the nature of taking structural measures like:
i) Embankments, flood walls, sea walls.
ii) Dams and reservoir
iii) Natural detention basin
iv) Channel improvement
v) Drainage improvement
vi) Diversion of flood waters

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Embankments, flood walls, sea walls
The most common and generally economical form of protection to provide immediate
relief from inundation is construction of embankment. The embankment system along
the river is planned to restrict the river in its existing course and they are designed to
avoid over-flowing of banks by increasing the channel capacity to pass the probable
floods. Generally, these are constructed with easily available earth in the nearby area.
The embankments of the pre-independence period and those came up after
independence through plans have provided considerable protection to life and property
of people living in flood plains.
As embankments prevent passage of river water into adjoining area even during high
floods which otherwise could have been inundated by silt laden river water, the
adjoining land is deprived of the fertilizing effect of silt, But there is no conclusive
evidence to establish the so-called fertilizing effect of silt. It is also a fact that sometimes
flood waters when spread over the flood plains adversely affect productivity of the land.
Also, in the case of embankments when constructed along the river banks, the flood
wave movement becomes restricted which causes general increase in flood stages
upstream of the embanked section. In alluvial reach, the embankments are continuously
threatened by erosion. The progressive of bed level requires progressive rise of the
embankment to ensure protection.
Embankments attract new settlements as a result of protection from floods offered by
them. State Governments have been very slow on maintenance of these structures due
to inadequacy of funds. Another problem is that due to unprecedented rains, if a breach
occurs, the effect of such a flood to the settlements will be unexpected and devastating.
Such breaches are reported from the States of Bihar, Assam, U.P. and West Bengal.
Proper maintenance of the embankments involving the beneficiaries and educating the
masses on the consequences of occupying the flood plains are necessary.
The benefits of embankments and embankment scheme in reducing distress and
damage due to floods are very evident. The benefits achieved for the some case of the
kosi project is as follows:
Kosi is a perennial river originating from Himalayas in Nepal whose three main streams
viz. the Sun Kosi, the Arun Kosi and the Tamur Kosi meet at Triveni in Nepal to form
Sapta Kosi or simply called as Kosi in the plains of Bihar. The notorious meandering
behaviour of Kosi is apparent from the fact that it has changed its course for a width of
about 112 km its lower reach in Bihar in a period of about 250 years, as a result of
which the flood problem faced by people living in the area was acute. A barrage was
constructed in 1963 for irrigation, power and regulated flow downstream. Flood
embankments on both sides of the river were constructed arresting its unique
translatory movements giving a great sense of security to the people of the area which
is apparent from the fast changing outlook in the districts of Purnea, Saharsa and
Darbhanga and, therefore, giving protection to an area of about two lakh ha in Bihar.

The flood embankments on both the banks of Kosi river which were mostly completed
as early as 1957 have on an average protected 1.17 lakh acres of land in Darbhanga
and 4.11 lakh acres in Saharsa districts of Bihar from the ravages of flooding. Kharif
crops on this land were formerly badly damaged and even Rabi sowing was sometimes
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affected by standing water and excessive moisture. Severe damage was also caused to
properties like building, orchards etc. Prevention of flooding in this area on account of
the project has rendered following incidental benefits:
i) Construction of a network of metalled roads improved communication and there by
addition to the convenience and prosperity of the people.
ii) Communications on the Mansi-Supaul and Saharsa-Purnea sections of the North
Eastern Railway, which were formally cut off in the wet season, are now possible
throughout the year. The longer running period will mean a rise in railway earnings from
fares and freights. Villagers served by these lines will have better facilities for carrying
their produce to markets.
iii) Replacement of improvised and temporary thatched houses of private individuals,
commercial concerns and govt. Departments by pucca buildings reflecting a better
standard of living and sense of security.
iv) Reclamation for cultivation of large areas of land which were formerly infested with
‘Kans and Pater’
v) Opening of small-scale industries and even major factories like the sugar factory
proposed at Banmankhi.
vi) Reduction of flood and waterlogging and consequential improvement in general
health.
vii) Kosi barrage has opened up all weather communication between Saharsa-Purnea
district on the bank and Darbhanga district on the other bank.
viii) A metalled road from Bathnaha to Bhimnagar had been constructed by the project.
This road provides much-needed means of communication in this locality.
In addition to benefits to Bihar (India) from the project, Nepal is also drawing large
benefits from it through protection from flood, stability of river in the upstream to some
extent and better communication system at flood time apart from power and irrigation
facility.
The Programme Evaluation Organisation of the Planning Commission undertook
evaluation of the embankment projects with a view to assess the economic benefits of
the projects. They also substantiated benefits from the project.
The embankments, however, have created some potential dangers to the zone inside
embankments, which is liable to experience greater threats of floods than before. The
area lying within 5 km of left embankment is submerged under water. Besides, the
problem of water logging also needs to be separately addressed and necessary
measures taken.

Dams and reservoir

Human issues involved in the case of dams and reservoirs are evacuation and
resettlement of people in the reservoir area, environmental impacts due to
developmental activities and increase in population etc. Consequences of dam failure-
possible damages to life and property in the downstream and human encroachment on
the flood plains due to the security provided by dams are also to be taken into account.
While planning all the above works, impact due to the scheme on its surrounding and on
the settlements in the downstream area need be taken into account.

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Maximum attention is to be given while framing reservoir regulation policies so that
optimum utilisation of water resources is possible and at the same time flood control
and issues related to the people living in the downstream of the reservoir are taken care
of.
Construction of dams and reservoirs is adopted as a major activity to control floods by
storing flood water so that the stored water could be released subsequently when the
flood has receded and the downstream river channel is in a position to contain the flow
without causing floods. The main advantage reservoirs is that apart from moderating the
flood peaks, the stored water can be used for multipurpose uses such as irrigation,
power generation, industrial requirements and domestic uses etc. In the case of flood
control reservoirs, proper reservoir regulation schedule can be worked out for optimum
benefit from the project as a whole from the flood control point of view, and it is
advisable that specific flood cushion is allocated in the reservoir although incidental
benefit of flood control to some extent is available from any reservoir scheme.

6.2.9 Non-structural measures for flood management

The present trend to reduce the losses incurred by flooding is equally towards non-
structural measures. This section examines some such techniques.

Flood plain management and zoning

Heavy encroachment of flood plains has been responsible for increasing trend of
damage over the years. The basic concept of flood plain management is to regulate the
land use in the flood plains in order to restrict the damage due to floods, while deriving
maximum benefits from the same. This is done by determining the locations and the
extent of areas likely to be affected by floods of different magnitudes/frequencies and to
develop those areas in such a fashion that the resulting damage is minimum in case
floods do occur. Flood plain zoning, therefore, aims at disseminating information on a
wider basis so as to regulate indiscriminate and unplanned development in flood plains
and is relevant both for unprotected as well as protected area. Flood plain zoning
recognizes the basic fact that the flood plains are essentially the domain of the river,
and as such all developmental activities in flood plains must be compatible with the
flood risk involved.
The basic concept of flood plain zoning is to regulate the land use in the flood plains in
order to restrict the damage by floods which are bound to occur from time to time. Flood
plain zoning, therefore, aims at determining the locations and the extent of areas likely
to be affected by floods of different magnitudes/frequencies and to develop those areas
in such a fashion that the resulting damage is reduced to the minimum. It, therefore,
places limitations on indiscriminate and unplanned development of both the unprotected
as well as protected areas. In the former case, boundaries of restricted areas are
established to prevent indiscriminate growth; while in the protected areas, only such
categories of development can be allowed which will not involve unduly heavy damage

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in case of failure of the protection provided, while ensuring that the valuable flood plains
are simultaneously put to development use.
Flood plain zoning is not only necessary in the case of floods caused by rivers but is
also useful in reducing the damage caused by drainage congestion, particularly in urban
areas, where on grounds of economy and other considerations, urban drainage system
is not designed for the worst possible conditions and presupposes some damage during
storms whose magnitude exceeds that for which the drainage system is designed.
The steps involved in implementation of flood plain zoning measures could be broadly
indicated as follows:
i) Demarcation of areas liable to floods
ii) Preparation of detailed contour plans of such areas on a large scale (preferably
1:15,000) showing contours at an interval of 0.3 to 0.5 metres
iii) Fixation of reference river gauges and determination of areas likely to be
inundated for different water levels and magnitudes of floods
iv) Demarcation of areas liable to flooding by floods of different frequencies like
once in two years, ten, twenty, fifty and hundred years. Similarly, area likely to be
affected on account of accumulated rainwater for different frequencies of rainfall like
5,10,25 and 50 years
v) Delineation of the types of use to which the flood plains can be put to in the light
of (i) to (iv) above with indication of safeguards to be ensured.
The need for flood plain zoning has been recognized in the past also. As far back as
1973-74, Central Water Commission had prepared guidelines for flood plain zoning
which were approved by the Central Board. Since the implementation of these
guidelines needed statutory backing, CWC also prepared a model draft bill which was
circulated in 1957 by the then Ministry of Irrigation, to all the States for enacting
legislation.
The Rashtriya Barh Ayog (1980) in its report has recommended that Flood Plain
Management measures should be undertaken, wherever necessary legislation enacted
in other States. However, the response from States except Manipur has not been
encouraging. Manipur enacted a legislation in Sept., 1978 which came into force in
Dec., 1985.
One of the reasons advanced by the State Governments for non-implementation of
flood plain zoning measures has been the non-availability of survey maps on suitably
large scale to enable proper demarcation of flooded areas. To overcome this difficulty,
Central Water Commission had initiated in 1978 programme for such surveys under the
Central Sector through the Survey of India to assist the State Governments in the
preparation of flood risk maps. These surveys cover areas along main Ganga, Yamuna,
Ramganga, Roopnarayan, Jalangi and other flood prone rivers of West Bengal,
tributaries of Brahmaputra like Burhi Dehing, Desang and Dikhoo, Sutlej and Ravi etc.,
which were taken up in a phased manner as per the priorities indicated by the States.
However, the programme has now been discontinued at Central level. With the
available data/maps, it should now be possible for the State Govts. to make a start and
demarcate the zones for different flood frequencies.
This is an area where immediate attention of all the State Governments has to be
attracted considering the extent of human issues involved. With the availability of
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remote sensing maps, preparation of flood risk maps has become easier. The need of
the hour is to prepare flood risk maps for all the frequently flood prone river plains in the
country, enact and enforce laws for implementing the zoning regulations, constant
monitoring of the flood situation using remote sensing and to plan mitigating measures
accordingly.

Flood Proofing
Flood proofing measures help greatly in the mitigation of distress and provide
immediate relief to the population in flood prone areas. It is essentially a combination of
structural change and emergency action, not involving any evacuation. The techniques
adopted consist of providing raised platforms for flood shelter for men and cattle and
raising the public utility installations above flood levels and other facilities to make
various essential services flood proof so that the miseries of people can be reduced to
minimum even when flooding occurs.

Flood forecasting and warning

Flood forecasting enables forewarning as to when the river is going to use its flood
plain, to what extent and for how long. As per strategy of laying more emphasis on non-
structural measures, Central Water Commission has established a nationwide flood
forecasting and warning system. With reliable advance information/warning about
impending floods, loss of human lives and moveable properties, human miseries can be
reduced to a considerable extent. People and cattle can be shifted to safer places.
Similarly, valuable moveable properties can be removed to safer places beyond area to
be inundated. Large number of reservoir schemes to harness water resources for
irrigation, power etc. were undertaken in the country during various plan periods.
Realising the great potential of reservoirs in impounding floods and regulating the flows
downstream for flood moderation, flood control has been sought to be achieved as one
of the objectives in multi-purpose dams by providing flood cushion. Inflow forecasting for
these reservoirs is very important for optimum reservoir operation.

Present flood forecasting network in India

Flood forecasting and flood warning in the country commenced in a small way in the
year 1958 with the establishment of a unit in the Central Water Commission (CWC),
New Delhi, for flood forecasting for river Yamuna at Delhi. This has by now grown to
cover most of the flood prone interstate river basins in the country. This organization is
presently responsible for issuing flood forecasts at 157 stations of which 132 stations
are for river stage forecast and 25 for inflow forecast.
The flood forecasting system of CWC functions under Member (River Management).
Seven field offices of Chief Engineers, ten offices of Superintending Engineers and
nineteen divisional offices are in charge of management of the forecasting work. These
offices are responsible for hydrological and hydro meteorological data collections such
as gauge, discharge and rainfall data, their transmission from field stations to the central
control rooms, formulation of forecasts and dissemination to various concerned
Central/State Governments, Media and other users. Forecast about water level in river
likely to be attained as a result of flood and volume of inflow to reservoir is issued by

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concerned officers everyday in the morning. The forecasts are also transmitted to CWC
headquarters at New Delhi where daily bulletins are prepared for the country as a whole
and sent to all concerned departments of the Government.

According to the present norms of the Central Water Commission, a forecast is

considered to be reasonably accurate if the difference between forecast and
corresponding observed level of the river lies within ± 15 cm. In case of inflow forecasts,
variation within ± 20 percent is considered acceptable. On an average, about 6,000
flood forecasts are issued every year with a maximum of 7,943 forecasts issued during
the year 1998. The forecasts issued by CWC have been consistently accurate as a
result of which the flood forecasting and warning services have rendered immense
benefit to the people in the flood prone areas.
Like the river stage forecasts, the inflow forecasts issued by CWC have also been
consistently accurate. This has provided immense benefit to the authorities of
concerned dams and barrages for systematic operation of the reservoirs for optimum
utilization of the water resources and for the control of floods.
However, proper integration of the flood forecasting system with disaster mitigation
works can go a long way to reduce flood damage and alleviate distress to the people
affected by flood. Also, where the warning messages are utilized with other non-
structural measures like flood plain zoning activity and flood fighting in a comprehensive
manner, the outcome of the forecasting and warning system can become more
effective.

Flood fighting
Flood fighting covers building temporary dykes along the river, dowel bunds on the
banks, closing small breaches immediately, attending to scour, wave wash, sand boils
etc. evacuating goods and equipment out of the reach of flood zone, protecting
equipment with plastic sheets etc. When floods occur, the existing facilities for water
supply and sewerage get disrupted affecting the health of the population. The
inundation and deterioration of the quality of food grains, destruction of agricultural
crops and health of livestock may lead to famine or at least nutritional deficiencies.
Stagnant water becomes the breeding ground for mosquitoes affecting public health.
Public health operations should ensure availability of supplies and equipment, co-
ordination with other organisations engaged in disaster relief and procedure for
immediate mobilisation of personnel to eliminate health hazards. Flood fighting
measures normally involve:
• Strengthening of Central, State and District Flood Control Rooms.
• Evacuation of flood victims.
• Air dropping of food packers.
• Close review of flood relief measures.
• Release of emergency funds to local bodies and thence to the flood victims.
• Supply of food and other rations.
• First aid and health operations.
• Supply of essential commodities like Kerosene, oil, petrol etc.
• Plugging of breaches.

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• Restoration of road/rail links.
• Restoration of tube wells and other agricultural machinery.
• Pumping out water from ponds and low-lying areas in cities/villages.
• Restoration of public assets such as roads, bridges, irrigation systems and
structures, power installations, public buildings, municipal roads, sewerage and water
supply schemes, paved streets and drains etc.
• Voluntary efforts by Red-Cross, Home-Guards, Panchayats, local people etc.
Most of the above activities are of immediate nature. Participation by voluntary
organisations and local people are necessary for flood fighting. There is a need to give
training to voluntary organisations and other non-governmental organisations in the
field. All the above issues are directly aimed at reducing the losses due to flood to life
and property.

Flood insurance
Flood insurance has several advantages as means of modifying loss burden. The
insurance does not reduce the flood loss potential directly, but it provides a mechanism
for spreading the loss over large number of individuals. It is advantageous both to the
public and the Government.
So far, flood insurance has not been adopted widely in India. Though flood risk has
been included in ‘cover’ issued by the General Insurance Companies in India, it is more
popular in urban areas and big towns where damage due to inundation caused mostly
by excessive rainfall is taken care of. The insurance companies have also not been able
to arrive at different rates of insurance premium for different flood prone regions in the
country. As such, they continue to charge uniform rate irrespective of the fact that
property was located in high flood risk area compared to the other areas. The insurance
companies are facted with a difficult choice. If they levy uniform rates in all areas, the
people in flood prone areas would most likely take out the policy which may become too
large a burden. If an attempt is made to charge rates proportionate to the flood risk, the
premium may work out much more than what the property owner might be willing to
pay. Another problem being faced by the insurance companies is regarding the
assembling of basic data for working out a fair and equitable premium for all areas
according to flood risk. The insurance cover works successfully for a class of people
who are subjected to such risks more or less equally. In case of floods, the risk of loss
even in areas liable to flood is not equal. For example, those owning land or property at
lower elevation in a flood plain are subject to higher risk both in magnitude as well as in
frequency. Therefore, those living at high levels would not be equally willing to obtain
insurance cover, at the same rate. It is quite a difficult task to accurately adjust
insurance premium. All these difficulties need to be sorted out and there is an urgent
need to make insurance schemes attractive to insures and the insured.

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 Module
6
MANAGEMENT OF
WATER RESOURCES

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 LESSON
3
REMOTE SENSING AND
GIS FOR WATER
RESOURCE
MANAGEMENT
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Instructional objectives:
On completion of this lesson, the student shall learn about:

1. The techniques of Remote Sensing and Geographic Information System (GIS)

2. Different types of remotely sensed images
3. Application of Remote Sensing in water resources engineering
4. Application of GIS in water resources engineering

6.3.0 Introduction
The term Remote Sensing is applied to the study of earth’s features from images taken
from space using satellites, or from nearer the earth using aircrafts. The technique of
remote sensing has picked up in the past half a decade, largely due to the availability of
digital computers, improved communication systems, digital imaging techniques and
space technology. Remotely sensed data can be said to have its origin in photography,
where the information about a target area is interpreted from photographs. Later this
technique was extended to aeroplane - borne cameras giving rise to the science of aerial
photography. This technique is still used, but largely the signal cameras have been
replaced by Laser operated ones where the reflectance of a Laser beam projected from
the bottom of the aircraft is sensed by electronic sensors.
In this chapter we shall discuss remote sensing using satellite as India has strived ahead
in this field and made good use of satellite images. The satellite launching program of our
country is one of the most ambitious in the world, and is still continuing to be so in the
future as well. Amongst other fields, the Water Resources Engineers have benefited
greatly by using satellite imaging techniques, some applications of which have been
highlighted in this chapter.
The other topic that is discussed in this lesson is the Geographic Information System
(GIS) that has wide applications in planning any spatially distributed projects.
Fundamentally, a GIS is a map in an electronic form, representing any type of spatial
features. Additionally, properties or attributes may be attached to the spatial features.
Apart from its spatial data analysis capabilities, it provides an interface to remotely
sensed images and field surveyed data. This technique has specifically benefited the
Water Resources Engineers, which has been discussed in some detail.

6.3.1 Remote sensing through satellites

Remote sensing means assessing the characteristics of a place (usually meant as the
surface of the earth) from a distance. Though this term was coined during the 1960’s,
similar technology had been practiced earlier like fitting a camera to a balloon and
allowing it to float over the earth’s surface taking pictures, which may then be developed
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and interpreted for specific purpose like geology, agriculture, forestry etc.
Photogrammetry, that is, taking pictures of the land surface from a low flying aircraft and
comparing subsequent pictures to obtain the terrain relief has been extensively used in
the last century and many books have been written on the subject.
In satellite remote sensing, too, cameras are fitted to the orbiting satellite and are
focussed towards the earth. However, the cameras are special in the sense that they are
sensitive to other wavelengths of the electromagnetic spectrum as well. As may be
observed from Figure1, the electromagnetic spectrum identifies the wavelength of the
electromagnetic energy, of which the visible portion (or light) occupies only a small
portion. Actually, electromagnetic energy refers to light, heat and radio waves. Ordinary
camera or the human eye are sensitive only to the visible light. But the satellites are
equipped with Electromagnetic Sensors that can sense other forms of electromagnetic
radiations as well. This includes not only the Blue (0.4-0.5μm), Green (0.5-0.6μm) and
Red (0.6-0.7μm) of the spectrum but also longer wavelength regions termed as the
Infrared (IR) spectrum (0.7-1000μm), which can again be further subdivided into the
following:
a) Photographic IR : 0.7-0.9μm
b) Very near IR : 0.7-1.0μm
c) Reflected/Near IR : 0.7-3.0μm
d) Thermal IR : 3.0-1000μm
Still longer wavelength is the microwave portion of the spectrum, which extends from
3000μm to 3m. The common remote sensing systems operate in one or more of the
visible, reflected-infrared, thermal-infrared and microwave portions of the spectrum.

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6.3.2 Interaction of electromagnetic radiation and earth
Electromagnetic energy of the sun incident on the earth’s surface reaches fully upto the
top of the atmosphere. However, as illustrated in Figure 2, not all of this energy reaches
the surface of the earth, since part of the energy gets either scattered, absorbed or
reflected by the atmosphere or cloud cover, if any. Only a part is transmitted upto the
earth’s surface. Specifically, it may be said that although the electromagnetic radiation
reaching the top of the atmosphere contains all wavelengths emitted by the sun, only
specific wave bands of energy can pass through the atmosphere. This is because the
gaseous components of the atmosphere act as selective absorbers. Molecules of different
gases present in the atmosphere absorb different wavelengths due to the specific
arrangement of atoms within the molecule and their energy levels. The main gaseous
component of the atmosphere is nitrogen, but it has no prominent absorption features.
Oxygen, Ozone, Carbon Dioxide and Water Vapour, the other major components absorb
electromagnetic wavelengths at certain specific wavelengths. The wavelengths at which
electromagnetic radiation are partially or wholly transmitted through the atmosphere to
reach the surface of the earth are known as atmospheric windows, as shown in Figure 3.
Since these radiations reach the surface of the earth, they are useful for remote sensing
as they would be reflected or absorbed by the features of the earth giving the typical
signatures for the sensors in the satellite (or any other space borne device) to record.
This is shown graphically in Figure 4.
The remote sensing system sensors are designed in such a way that can capture
information for those wavelengths of electromagnetic radiation that occur within the
atmospheric windows.

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6.3.3 Interaction of electromagnetic radiation with a surface
When electromagnetic radiation strikes a surface, it may be reflected, scattered, absorbed
or transmitted. These processes as not mutually exclusive: a beam of light may be
partially reflected and partially absorbed. Which processes actually occur depends on the
wavelength of the radiation, the angle at which the radiation intersects the surface and the
roughness of the surface. Reflected radiation is returned from a surface at the same
angle as it approached, the angle of incidence thus equals the angle of reflectance.
Scattered radiation, however, leaves the surface in all directions. Whether or not incident
energy’s reflected or scattered is partly a function of the roughness variations of the
surface compared to the wavelength of the incident radiation. If the ratio of roughness to
wavelength is low (less than one), the radiation is reflected whereas, if the ratio is greater
than one, the radiation is scattered. A surface which reflects all the incident energy is
known as a Specular reflector whereas one which scatters all the energy equally is a
Lambertian reflector. Real surfaces are neither fully specular nor fully lambertian.
However, for remote sensing purposes, a Lambertian nature is better. A remotely sensed
image of a fully specular surface gives a bright reflectance (or signature) for one position
of the camera and dark image at other positions. If the surface is uniform lambertian, then
the reflectance obtained for the surface will be same irrespective of the location of the
camera because the radiation from the surface would be scattered equally in all
directions. Most natural surfaces that are observed using remote sensing systems are
approximately lambertian at visible and infrared wavelengths.

6.3.4 Interaction of electromagnetic radiation with earth surface

features
From the general discussion on the nature of interaction of electromagnetic energy with
any surface, we turn on to the earth features as these would be useful in Water
Resources Engineering.
As observed from Figure 5, it is seen that a part of the electromagnetic energy reaches
the earth’s surface, a part of it gets absorbed by the body, a part gets transmitted within
the body, and a part gets reflected from the surface of the body. The proportion of energy
that is reflected, absorbed and transmitted varies with the particular earth feature, like
whether it is vegetation, water, urban landscape, etc. Besides, the proportion of energy is
also dependent on the wavelength of the electromagnetic spectrum that is interacting with
the surface. Thus, for a particular feature, the proportion of energy that is reflected,
absorbed or transmitted varies with the wavelength that is interacting.
This means that two different features may reflect equal proportion of energy in one
wavelength range and may not be separately identified but for another wavelength range
their difference reflectance may allow a sensor to distinguish between the two features.
This variation in interaction of electromagnetic energy with any surface can be explained
in the way we distinguish objects by separate colours. As we know, the wavelengths in
the visible range of the spectrum strike all surfaces, but we observe different colours
because each surface reflect only a particular wavelength and absorb the rest.
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Most of the sensors in remote sensing systems also operate in the wavelength regions in
which the reflected energy predominates and thus the reflectance property of surfaces is
very important. Of course, the sensors do not capture only the reflected energy in the
visible range of wavelength but different sensors are designed to capture the reflected
energy in other ranges of wavelengths as well.
The reflectance characteristics of the different features of the earth surface may be
quantified by measuring the portion of incident energy that is reflected by a surface. This
reflected energy is measured as a function of the wavelength and is called Spectral
Reflectance. Quantitatively this is defined as the ratio of the energy of the wavelength
reflected from an object and the energy that is incident upon it.
Spectral reflectance of any object usually varies according to the wavelength of the
electromagnetic radiation that it is reflecting. A graph showing the spectral reflectance of
an object for various wavelength is known as a Spectral Reflectance Curve (Figure 6).
The pattern of a Spectral Reflectance Curve gives an insight into the spectral
characteristics of the object. It also helps in selecting the wavelength bands which may be
suitable for identifying the object.

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6.3.5 Spectral signature of earth features
For optimum use of remotely sensed data in various wavebands in identification and
differentiation of different objects or features on earth, it is important to have a thorough
knowledge and understanding of their spectral reflectance characteristics. Usually, the
features that are classified through satellite remote sensing may be grouped into
inanimate objects like soil, minerals, rock, water, etc. or animate object which is usually
vegetation. Soil is a heterogeneous mixture of minerals, containing considerable amount
of organic matter and often moisture. The proportion of these determine the spectral
characteristics of the particular soil type. Rocks are assemblages of minerals and hence
the reflectance spectrum of rocks is a composite of individual spectra of its constituent
minerals. As for vegetation, the reflectance spectra vary according to the freshness of the
leaves. Thus the characteristics of the reflectance of various earth features for different
electromagnetic wavelength bands is used to identify different earth objects and are
hence also known as Spectral Signatures. A study of the spectral reflectance
characteristics of natural earth surface features shows that the broad features are
normally separable. In the following paragraphs, we discuss the spectral signatures of
certain typical earth features, natural and artificial.

Vegetation
The spectral signature or reflectance of healthy green vegetation is as given in Figure 6.
In the visible range of electromagnetic wavelength spectrum, it has an absorption band in
the blue and red parts because of the presence of chlorophyll. One may notice these at
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0.45μm and 0.65μm. Even within the green part of the spectrum, only 10 to 15 percent of
the incident light is reflected. The reflectance peak is seen to be at 0.54μm, which is in
the green wavelength region.

The reflectance property of healthy vegetation is seen to be much larger (40 percent or
more) in the infrared portion of the spectrum and is nearly constant from 0.7μm to about
1.3μm. In this range of electromagnetic spectrum, the reflectance variation is different for
different plants and also between healthy vegetation and stressed vegetation. Hence, a
reflectance measurement in this range permits one to discriminate between different
species of vegetation, though this differentiation is not very apparent in the visible range
of the spectrum.
Beyond 1.3μm, low spectral reflectance for vegetation is noticed at 1.4μm, 1.9μm and
2.7μm with intermediate peaks at about 1.7μm and 2.2μm.

Soil
The spectral signature of soil is simpler in soils compared to that by vegetation since all
the incoming radiation is either reflected or absorbed due to very little transmittance. A
typical reflectance curve for soil shows increase in wavelength in the visible and near-
infrared regions (Figure 6).

The reflectance property of soil varies with soil moisture content, texture (that is, the
relative content of sand silt and clay that makes up the soil), surface roughness, colour,
content of organic matter, presence of sesquioxides, etc. In the visible portion of the
spectrum, there is a distinct decrease in reflectance as moisture content increases, since
more moisture in soil makes a soil appear darker causing less reflectance. Soil texture
influences the spectral reflectance by the way of difference in moisture holding capacity
and due to difference in the size of the particles. Soils with higher organic matter appears
as light brown to grayish in colour. The reflectance characteristics in the visible region of
the electromagnetic spectrum has been observed to be inversely proportional to the
organic matter content. The presence of iron oxide in soil also significantly reduces the
reflectance, at least in the visible wavelength.

Water
For water resources engineer, locating areal extent of water bodies like lakes, rivers,
ponds, etc. from remotely sensed data is an important task. The spectral response from a
water body is complex, as water in any quantity is a medium that is semi-transparent to
electromagnetic radiation. Electromagnetic radiation incident on water may be absorbed,
scattered and transmitted. The spectral response also varies according to the
wavelength, the nature of the water surface (calm or wavy), the angle of illumination and
observation of reflected radiation from the surface and bottom of shallow water bodies.
Pure clear water has a relatively high reflectance in the visible wavelength bands between
0.4 and 0.6μm with virtually no reflectance in the near-infrared (0.7μm) and higher
wavelengths (Figure 6). Thus clear water appears dark on an infrared image. Therefore,
location and delineation of water bodies from remotely sensed data in the higher wave
bands can be done very accurately.

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Water containing heavy sediment load, as in the water in the estuary, has a turbid
composition. The sediment suspended within the body of water tends to increase the
reflectivity at longer wavelengths of the visible part of the spectrum, that is, in the
yellow/red range.

Man-made structures
Sometimes it is required to identify artificial structures that is useful to an engineer. For
example roads, paved surfaces, canals, and even dams and barrages can be identified
from remotely sensed images by their reflectance characteristics. Many of these,
especially linear features, are clearly discernible in the visible waveband of
electromagnetic spectrum.

6.3.6 Remote sensing and imaging systems

The remotely sensed images are captured by sensors fitted to satellites (and at times
below aircrafts) that work on two basic technologies (Figure 7). One of these, the Passive
System, records the reflected electromagnetic energy of the earth, the source of the
energy being the radiation of the Sun. The other, called the Active System, employs its
self-generated pulses and records the reflected pulse. These two systems may be
compared to taking photographs in sunlight and with flashlight respectively. The active
remote sensing systems mostly use radars that emit radiation in the microwave band of
the electromagnetic spectrum. This system is useful in cases where passive systems do
not give sufficient information. For example, images of flood inundated areas are
important to a Water Resources Engineer. However, most of these images taken by the
passive systems are blocked by cloud cover since incidents of floods are most common
during the monsoons and are almost coincident with heavy cloudy days. Radar based
systems, on the other hand, are able to penetrate the cloud cover and give a clear picture
of the flood inundation extent.

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The images recorded by a remote sensing sensor is a digital map of the scene that
comprises of a regular grid array of squares, called pixels, with an unique value attached
to each (Figure 8). The value of each pixel is proportional to some property, like average
reflectance, recorded by the sensor for the equivalent area on the ground. The pixel
values normally range from 0 to 255. For example, images recorded in the visible
spectrum are usually a combination of three values for each pixel, one each for blue,
green and red colours. For each colour, the pixel has a value ranging from 0 to 255. A
pixel that records the image of a pure white area, will have the pixel values of all the three
bands as 255. For a pure black region, the three individual bands would have values of 0.
A blue looking area shall have the value 255 for the image that records the blue colour,
and 0 for green and red.

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Similarly, sensors record pixel values in the infrared areas of the electromagnetic
spectrum in passive systems and in the microwave areas in the active systems. The
Indian Remote Sensing (IRS) satellites are, till now, equipped with active sensors that
record images in four wave bands and others that record in a single wave band. The
latest group of satellites available for earth imaging are the IRS-IC/ID. There are three
sensors in these satellites, and each has its own characteristics, as given below.
• LISS (Linear Imaging Self-Scanning Sensor)-III. This medium resolution sensor that
records data in four spectral bands: Two in visible range (0.52-0.59μm and 0.62-0.68μm),
one in near infrared range (0.77-0.86μm), and one in short wave infrared (1.55-1.70μm)
region. The spatial resolution, that is, the pixel size of the images are 23m for the first
three bands and 69m in the last band.

• PAN (Panchromatic, or single wave band). This is a high resolution (5.8m pixel size)
sensor operating in the 0.50-0.75μm range.

• WFS (Wide Field Sensor). This is a coarse resolution (188m) sensor operating in two
bands: visible (0.62-0.68μm) and near infrared (0.77-0.86μm).

6.3.7 Spectral signatures

By deducing earth features from Multi Spectral Scanned (MSS) images the Water
Resources Engineer may derive various important information of a wide region of the
earth that may be useful for analysis. Hence, primarily, the earth features have to be
identified from MSS images based on the Spectral Reflectance characteristics or
signatures of various objects as discussed in Section 6.3.5.

An MSS data of a region comprises of two or more images of the same area that has
been scanned by the remote sensing sensor. For example, the LISS-III sensor shall give
four images of the area corresponding to the four spectral bands in which the data is
collected. Each of these images comprise of data stored for each pixel, which is in the
form of a Digital Number (DN) corresponding to the pixel’s average reflectance property in
the particular waveband. The DN varies from 0 to 255, and hence, each image may be
printed or discussed in a gray-scale. However, all the four images for a region printed or
displayed in gray-tone may not be useful individually. Hence, a combined image is
produced, called the False Colour Composite (FCC) image, which combines the
characteristics of the images of all the four bands.
An FCC image which simulates a colour infrared image, the visual interpretability of
features is better than that from image of each band taken separately. The typical colour
signatures of some of the features on the surface of the earth in standard FCC is given in
the following table:

Features on the earth surface Colour signature

Healthy reflection
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 Broad leaf type Red to magenta
Needle leaf type Reddish brown to purple
Stressed vegetation
Pre-visual stage Pink to blue
Visual stage Cyan
Water
Clear Dark blue/black
Turbid due to sediments Light blue
Soil
Red soil/red bed outcrop Yellow
Moist soil Distinct dark tong
Sand-dunes Yellow/white
Land-use
Uncultivated land Blue/white
City/town Blue
Others
Cloud/snow White
Shadow* Black with a few visible details
∗Shadow is not very significant in MSS satellite images with the present day spatial
resolution as the scales of features are too small to aid in recognition.

Digital interpretation
Visual image interpretation requires the person to have thorough knowledge of the
features being identified and their spectral reflectance characteristics. The technique is
subject to human limitation. Hence, another technique – the Digital method of image
interpretation – is often used in identifying earth surface features from remotely sensed
images. Infact, this comprises of a very important area, the details of which may be
obtained in standard textbooks on Remote Sensing and Image Processing. Here only a
brief account of the process is given below.
Primarily, this is possible due to the fact that an image actually comprises of a number of
pixels, each being assigned a Digital Number (DN) according to the average reflectance
of the corresponding ground area in the particular spectral band. Thus, an image is
nothing but a matrix of DNs. Computer algorithms are available in Image Processing
Software Packages that make use of these numbers to identify the feature of land
corresponding to each pixel. The numerical operations carried out on these digital images
are grouped as follows:
1. Pre-processing: Removal of flawed data, correction of image.
2. Image registration: Translation, solution or stretching of the image to match earth’s
true geometry.
3. Image enhancement: Improving images or image patches that suffer from low
contrast between pixel DN values.
4. Image filtering: Methods to identify clearly the boundary between two district
regions of separate reflectance characteristics.
5. Image transforms: Combination of one or more images of different spectral bands
of the same area.

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6. Image classification: Automatic categorization of pixels into various land-cover
classes.
Though digital image interpretation has the capability to classify earth surface features
with the help of a computer, it must be supplemented with ground truthing, that is,
verification of the interpreted regions with actual information gathered from the ground by
field survey.

6.3.8 Application areas of Remote Sensing in Water Resources

Engineering
The interpretation of remotely sensed images may provide valuable information to the
Water Resources Engineer, some of which are discussed below for various fields of
applications

Sl. Field of application Useful interpreted Helpful in

No. information
1. Irrigation Engineering Crop area, Crop yield, Estimating the amount
Crop growth condition, of irrigation water that
Crop areas that are water is to be supplied to an
stressed and are in need irrigated area over
of water different seasons
2. Hydrology Different types of soils, Estimating runoff from
rocks, forest and a watershed, where
vegetation of a water the land-cover type
shed, soil moisture and soil moisture
would decide the
amount that would
infiltrate
3. Reservoir Plan views of reservoir Estimating the extent
sedimentation extent at different times of of sedimentation of a
the year and over several reservoir by
years comparing the extent
of reservoir surface
areas for different
storage heights
4. Flood monitoring Flood inundated areas Flood plain mapping
and zoning
5. Water Resources Identification of wasteland Recent information
Project Planning (from MSS images), helpful in planning and
mapping of infrastructure designing of a water
features (from PAN resources project
images) like existing based on the present
roads, embankments, conditions of the
canals, etc. apart from project area
plan view of a river

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6.3.9 Geographic Information System (GIS)
A GIS is a computer application program that stores Spatial and Non-Spatial information
in a digital form. Spatial information for an area is what is traditionally represented in
maps which for a region, may broadly be classified as given in the following table. The
corresponding source of such data for our country is also indicated.

Sl. No. Spatial features of a region May be obtained from

1. • Elevation contours Survey of India, in the
• Drainage form of Topo-Sheets
• Location of roads, towns, villages
2. Soil map National Burean of Soil
Survey and Land Use
Planning
3. Geological map Geological Survey of
India
4. Latest information on land-use and land- Satellite imageries
cover, like
• Vegetation, forest, crops, etc.
• Towns, villages and other human
habitation
• Roads, Embankments, Canals
• Rivers
5. Maps of District, Block, Thana, Mouza, State Land Record office
Taluk, etc.
6. Location of ground water wells and Central or State Ground
corresponding water tables as observed Water Boards
over time

Non-Spatial data, also called Attributes, refer to information like demographic distribution
of a town or a village, width or identification tag of a road (like NH-6), daily discharge of a
river at a particular place, etc.
Thus, a GIS conveniently manages all variety of data of a given region in a single
electronic file in a computer. This is helpful to any regional planner, including that of a
Water Resources Project since all information is conveniently stored and accessed with
the computer. Further, though the scales of various printed maps may be different, a GIS
stores all of them in the same scale. Normally, different spatial features are stored in sub-
files, called layers. Hence, one may use the GIS to open all the layers showing all
thematic features. Else, one may display one or a few themes at a time by activating the
respective layers. For example, the land-use layer may be displayed along with elevation
contours, the other layers being kept off.
Important features of GIS software includes handling of spatial and attribute data, data
input and editing, data analysis and output of data, which are discussed briefly in the
following sections.
A GIS may be considered to comprise of the following components:

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• A software package, the components of which include various tools to enter,
manipulate, analyse and output data
• A computer system, consisting of the hardware and operating systems.

6.3.10 Handling of spatial and attribute data in GIS

There are two types of data storage structures in a GIS-Raster and vector. According to
the Raster system, the space is assumed to be divided into a grid of cells, with a certain
value attached to each cell according to the data that is represented by a grid of cells,
would be done by marking the corresponding cells black (and assigning a value 1), with
all other cells remaining vacant (that is, assigning a value of 0). In the vector system of
data storage, the particular point would be stored by the coordinates of the location. This
was an example of a point feature. Other types of geographic features include line, area,
network of lines and surface, which have been shown in Figure 9.

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It may be noticed that in the raster grid representation of an area, the size of the grids is a
choice of the person using the GIS. For example, in representing the spatial information
of a town, a grid size of 10 to 25 m may be sufficient but for a state, 100 to 250 m would
be enough. Adopting a finer grid size would, naturally, provide a better representation of
data. But that would require a higher computer storage space, which therefore has to be
judged optimally.
For vector data representation, too, a better resolution of data may be achieved for line
features by selecting more number of points closely. This applies also for representing the
lines defining the boundary of an area. For surface representing more number of points
defining the elevation contours would result in a more precise definition of the region.
Attribute data is non-spatial, that is, it is not something that varies continuously in space.
This is actually the database that defines the spatial data. For example, the location of
ground water wells is a spatial data, but the water level record or variation of water level
with time is an attribute data of the particular well. Similarly, rivers may be represented as
a network of lines, but the width and average depth at different points would be
represented as attribute data.

6.3.11 Input and editing of data in GIS

The user of a GIS has to input data, whether Spatial (in Raster or Vector formats) or Non-
Spatial (usually in the form of tables). Spatial data, as shown in section 6.3.9, may be
obtained from different sources and in different formats. They may be input into a GIS in a
variety of methods, depending on the format in which they are being supplied. For
example, maps would usually be supplied in printed sheets but the satellite image of an
area or the land-use map derived from it would be in electronic, that is digital, form. The
latter may be directly transferred to a GIS but the former has to be Scanned and then
Digitized. Scanning means producing an electronic file of the image, which would usually
be a raster representation of the map. This may be done with the help of scanners that
are available from sizes of A4 (the smallest) to A0 (the largest). The scanned images are
not of much use to a GIS since it does not differentiate between the different objects
indicated in the image. For this, manual help is required in the form of Digitization, where
by a person uses a mouse over the scanned image to physically point to the various
features and store them in GIS format. In order to do this, the vectorization tools of the
GIS software would be used. Tabular attribute data may be directly transferred to a GIS
and attached to the corresponding spatial data with certain tools provided by the GIS
software. All the various data are stored in a GIS as layers, or themes.
After data input, the uses might have to edit some of the data to remove duplicacy,
redundancy, etc. of some of the vector data or to remove specks or ‘noise’ in raster data.
The errors in the vector data appear while undergoing the process of digitization and
therefore, has to be corrected before an analysis with the data is made. For example,
while digitizing the boundary of a reservoir from a map, the starting and ending points
may not be located right over one another. The GIS would not recognize the outline as a
closed boundary, and the reservoir plan cannot be defined as an area. Hence, an editing
has to be done to correct this deficiency. Errors in raster data appear due to a variety of
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reasons, one being the presence of aberration during data capture. For example, LISS-III
MSS imagery of an area used to classify land-use may be misrepresented by the
presence over some places, unless these are removed, they may lead to false
interpretation of land-use classification.
Once spatial and attribute data have been enclosed and edited, it may be necessary to
process the different data obtained through various sources in such a way, that all are
geometrically compatible.
Some of the mathematical transformations used in this process are:
1. Translation and scaling
2. Creation of a common origin
3. Rotation

6.3.12 Analysis of data in GIS

Once the derived data has been input in a GIS, they are analysed to derive meaningful
information. Infact, analysis is essential for any decision-making strategy that may be
derived from the stored GIS data. For example, imagine a GIS data that provides
locations of ground water wells of a region and their corresponding water levels measured
every month. This is overlain with the village boundary data of the region. By plotting the
ground water table surface for every month, it may be seen which villages consume more
water and when. In this simple example, the analysis is between two different data sets
but overlain in the same GIS.
More complicated analysis may be done by interacting more themes or data layers. For
example, if it is required to obtain the names of the villages that suffer from excess
groundwater depletion in summer and also whose population is more than 10,000 then
the population attribute data has to be considered in the query. Another example of using
three layers for data analysis includes that of finding the names of the villages that are
within 1 km distance from a river and also located at an elevation of 50 m or less. In this
case, the river feature has to be ‘buffered’ with a 1 km zone on either bank and the
surface area below 50 m elevation has to be plotted from the digitized contour map. On
top of this, the layer representing digitized boundaries of villages has to be overlain to get
the desired output.

Though the above examples are only limited to analysis of recorded data, considerable
scope lies in the use of GIS data along with mathematical modeling tools that mimic
physical processes. For example, watershed runoff model may be conveniently integrated
with GIS to provide answers like:
• Which areas of a watershed produce more runoff if a rainfall of a particular intensity is
given?
• If the land-use map of the area is overlain on the above is it possible to find out the
areas that are prone to excessive soil erosion?
Hence, a GIS database may become extremely useful, if coupled with a modelling
software. Much work on similar lines has been done by Prof. Maidment of University of
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Texas by integrating GIS with hydrologic process models. Interested users may visit the
following site for more information in the following web-site:
http://www.ce.utexas.edu/prof/maidment/GISHYDRO/home.html

6.3.13 Data output in a GIS

The most common form of output from a GIS is a map. In many cases, a thematic map
would be that illustrate the spatial variation or pattern in a particular variable. Apart from
maps, a GIS output may be in the form of table, like that that showing the names of
villages whose groundwater drawdown is more understandable may be output for the
decision-makers. For example, the ground water table contour may be output as a three
dimensional surface, which may provide a visual guide to the trend of the water table’s
dip.

6.3.14 Application areas of GIS in Water Resources

Engineering
There are many areas in Water Resources Engineering where GIS may be successfully
applied. Some examples have been given in this lesson in the previous sections, and
some more are illustrated below.

Project planning for a storage structure

In this example, a dam is proposed to be constructed across a river, for which the
following information may be desired:
• Watershed area contributing to the project site
• Reservoir surface area and volume, given the height of the dam
• villages that may be inundated under reservoir

For the above, the following themes may be stored in a GIS:

• Elevation contours of the watershed area, including the project site
• Satellite image derived land-use map of the watershed
• Village boundary map, showing location of habitation clusters

Using the above data, one may obtain desired in information as follows:
• Watershed area may be found by using the elevation contour data, and using a
suitable GIS software that has a tool to delineate the watershed boundary. Once the
boundary is identified, the area calculation tool may be used in the GIS software to
calculate the watershed area.

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• Reservoir surface area can similarly found using the area calculation tool. Volume
calculation tool of the GIS software may be used to find out the storage volume, which is
the space between a plane at the reservoir surface and the reservoir bottom.
• By overlying the reservoir extent over the village boundary map and the locations of
habitation clusters one may identify the villages that are likely to be inundated once the
reservoir comes up. The area of the cultivable village farms that would be submerged
may also be similarly identified, as it would be required to pay compensation for the loss
to the villagers.
• The amount of forest land that is going to be submerged may be identified by
overlaying the reservoir area map over the land use map, for which compensatory
afforestation has to be adopted.

Project planning for a diversion structure

Here, a barrage is proposed across a river to divert some of its water through a canal, for
which the following information may be desired:
• Location site of the barrage
• Location and alignment of the off taking canal
• Command area that may be irrigated by the canal

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