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Hydrology and Irrigation
Unit-4
Irrigation Engineering
Introduction
History of Irrigation
– As old as the civilization
– Originated in the semi-tropical and relatively arid regions
• Periodic overflow of the large rives followed by dry period
• Guide the overflow in ditches and bring it through canals to the fields
• Diversion of water from streams through canals
• These temporary dams were constructed using sand bags
– Reference to well irrigation in Rigveda
• Wells were full with water. Rope and pulley were used to fetch water
from the well. Water is then directed to broad channels, from there to
diverting channels and finally into the fields.
– 3rd and 4th Century BC
• Indian scholar Panini mentioned tapping several rivers for irrigation.
• Texts from the Maurya Empire era (3rd century BCE) mention that the
state raised revenue from charging farmers for irrigation services from
rivers.
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What is Irrigation?
• Process of artificially supplying water to the soil for growing
crops
– In accordance with the crop water requirement
– Throughout the crop period
• Includes
– Conservation and storage of the water,
– Carrying water from the source of supply to the irrigable area
– Distributing water to the lands
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Irrigation during Medieval India
• Rapid advances in the construction of canals and bunds
• Irrigation is said to be one of the major reasons for the
expansion of the Vijayanagar Empire in the 15th century
Irrigation in British India
• Major famines mandated irrigation
• Renovation , improvement and extension of existing works
• New projects: Upper Ganga Canal, Upper Bari Doab Canal
and Krishna and Godavari Systems
• Major canal works
Why irrigation?
1. Less rainfall
– When total rainfall is less than the water requirement of the crop
2. Non-uniform rainfall
– Non-uniform rainfall during the crop period
– Excess water during the rainfall period may be collected and used for
irrigation during the non-monsoon period
3. Growing perennial crop
– Perennial crops require water throughout the year
4. Multiple cropping
– More than one crop in a year🡪 non-monsoon crop requires irrigation
5. Commercial crop with additional water
– Commercial and cash crops requires more water
6. Controlled water supply
– Controlled supply 🡪 better yield
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Annual rainfall
Crop Water requirement
(mm)
Rice 900-2500
Wheat 450-650
Maize 500-800
Sugar cane 1500-2500
Groundnut 500-700
Tomato 600-800
Sunflower 350-500
Ragi 400-450
Benefits of Irrigation
1. Increase in Food Production
2. Protection from Famine
3. Cultivation of Cash Crops
4. Addition to the wealth of the country, Increase in prosperity of people
5. Generation of hydro-electric power
6. Domestic and industrial water supply
7. Elimination of mixed cropping
8. Inland navigation
9. Improvement in communication
10. Canal plantation
11. Improvement in groundwater storage
12. Aid in civilization
13. General development of the country
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ILL-EFFECTS OF IRRIGATION
1. Water-logging
– Over irrigation raises GWT- completely saturates crop root
zone- cut off normal air circulation in root zone-crop yield
reduces – later land becomes saline or alkaline and unfit
for cultivation.
2. Breeding Places for Mosquitoes
– Excess application of water, and leakage of water – ponds
and depressions get filled up – create breeding places for
mosquitoes – spread malaria.
3. Water pollution
Seepage to the groundwater carries nitrates leading to
GW pollution
3. Damp Climate
– Already damp and cold areas become more damper and
colder unhealthy climate – results in outbreak of diseases.
Cropping seasons in India
• Kharif Season
– Grown with the onset of monsoon and are harvested in September-
October
– Paddy, maize, jowar, bajra, tur (arhar), moong, urad, cotton, jute,
groundnut, soyabean etc.
– Mostly rainfed agriculture
– Supplementary irrigation may be needed to cope up with the in-between
dry spells
• Rabi Season
– Sown in winter (October to December) and harvested in summer (April to
June)
– Wheat, barley, peas, gram, mustard etc.
– Depends on the availability of precipitation during winter months
– Irrigation is an important factor for the success of rabi crops.
• Summer crop
– Grown In between the rabi and the kharif seasons
– Short duration crops such as watermelon, muskmelon, cucumber and
vegetables
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Sources of irrigation water
1. Surface water
2. Groundwater
• In India, more than 90% of the groundwater extraction
is for irrigation
• Supply water to more than 60% of the irrigated area in
the country
Classification of irrigation projects
Major irrigation schemes : CCA>10000 ha
Medium irrigation schemes: 10000 ha>CCA>2000 ha
Minor irrigation schemes: CCA <2000 ha
Gross irrigated area in India > 96.46 Mha and
Net irrigated area > 68.38 Mha
Net irrigated area from various sources in 2014-15
Source NIA (M.ha) % Contribution
Canal 16.18 23.66
Tank 1.72 2.52
Wells 42.96 62.82
Others 7.52 11
Total 68.38 100
https://www.researchgate.net/publication/340234257_Irrigation_in_India_Status_challenges_and_options
Jain et al., (2019) “Irrigation in India: Status, challenges and options” Journal of Soil and
Water Conservation,18 (4): 354-363, October-December 2019
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Sustainable irrigation
• Irrigation water demand is increasing rapidly
• Resources are degrading (both surface and ground
water resources)
• Sustainable methods
– Increase the irrigation efficiency
– Reduce the conveyance and application losses
– Conjunctive use of surface and groundwater resources
Learning Resources
1. Irrigation Engineering and Hydraulic Structures – S.K. Garg
2. Irrigation and water power Engineering- B.C. Punmia
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SYSTEMS AND TYPES OF
IRRIGATION
Scope of Irrigation
• Engineering aspects
– Storage, Diversion or lifting of canal
– Conveyance of water to the agricultural fields
– Application of water to agriculture field
– Drainage and relieving water logging
– Development of water power
• Agricultural aspects
– Depth of water necessity to various crops
– Distribution of water uniformly and periodically
– Capacities of different crops for irrigation water
– Flow of water in soil
– Reclamation waste and alkaline lands
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Learning objectives
• At the end of the class you will be able to
– Explain various types of irrigation
– Various methods of applying water to the fields
1. Types of irrigation
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Types of Irrigation
FLOW IRRIGATION
Water is supplied from a higher
elevation to lower elevation by
the mere action of gravity
LIFT IRRIGATION
• Water is lifted by some mechanical
or manual means such as pumps
• When water supply is at too low
level to run by gravity on to the
land
• Irrigation from well is an example
Flow Irrigation- Flow under gravity
Perennial irrigation
• Continuous supply in accordance
to the crop water requirement
throughout the crop period
• Through storage canal head works
and canal distribution system
Flood (inundation)irrigation
• Soil is kept submerged and
thoroughly flooded with water
• Soil is saturated
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Flow irrigation classification- Depending
upon the source
• Direct irrigation
• Storage irrigation
• Combined system
Flow irrigation
- Direct irrigation
• Water is directly diverted to
the canal without storing.
• A low diversion weir / barrage
across the river🡪 raises water
level 🡪 diverts the water to
the canal taking off from
upstream of the weir.
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Flow irrigation
- Direct irrigation
• Water is directly diverted to
the canal without storing.
• Smaller scale as there is no
control over the supply
• 1-2 main canals take off from
the river/ branch canal taking
off from main canal.
When to adopt?
• River is perennial and has a
normal flow throughout the
irrigation season.
• Flow is never less than the
irrigation requirement
Flow irrigation
- Storage irrigation
• A dam / storage weir is
constructed across the river to
store the water in the reservoir
• Bigger magnitude and expensive
• Various regulatory works and
cross-drainage works are
constructed
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Flow irrigation
- Storage irrigation
• Storage volume is decided
depending upon the water
requirement of crops,
hydroelectric power generation
and flow through river.
When to adopt ?
• It is adopted when river is not
perennial or
• Insufficient flow in the river
during certain period
Flow irrigation
- Combined system
• Water is first stored in reservoir
formed at the u/s of the dam 🡪
water power generation.
• The discharge from the power
house is fed back into the river
to the d/s of the dam.
• Pick-up weir is constructed in
the d/s to divert the water from
river to canal.
• Ex:- Kota dam and Kota barrage
on Chambal river in Rajasthan.
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Tone-diversion weir – Minumadai Canal
Types of irrigation
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2. Methods/ models of water application
• Surface irrigation
• Sub surface irrigation
• Sprinkler irrigation
• Drip irrigation
Uncontrolled or wild flooding
• Water is spread or flooded on a smooth flat land, without much
control or prior preparation
• Used where water is
abundant and
inexpensive
• Wasteful use of water
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Controlled Flooding
• Water is spread over the land, with proper methods
to control the depth of application
– Free flooding
– Contour laterals flooding
– Border strip flooding
– Check basin flooding
– Ring basin flooding
Free Flooding (Irrigation by plots)
• Commonly used in India
• Field is divided into a number of small sized level plots
• Water is admitted to the land at higher end and it is cutoff
once the lower end has sufficient depth of water
• Supply channels 🡪 Field channel
🡪 Waste channel
• Water is applied through the
feeding points along the laterals
• Applicable for both flat lands and
relatively steep lands
• For steeper slopes closely placed
laterals is required (Normal
spacing vary from 10 to 50m)
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Flooding by contour laterals
• Special case of free flooding
• Field channels or laterals are aligned approximately along
the contour lines
• Applicable for steeper terrains
Boarder strip flooding
• Land is divided into long parallel strips 🡪 borders
• Borders are separated by low ridges
• Boarders have uniform gentle slope in the direction of irrigation
• Each strip is irrigated independently by turning the water in the
upper end.
• Water spreads and flows down the strip in a sheet confined by
the border ridges
• Larger areas can be irrigated within a
short time
• Length of the border strip depends on
how quickly it can be wetted over the
entire length
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Check basin irrigation
• It is the most common method, also known as irrigation by plots
• The field is divided into smaller unit areas of nearly level surface
• Bunds or ridges are constructed around the area forming basins
• Water is applied to each basins to a desired depth can be
retained until it infiltrates into the soil.
Size of the basin
varies from 10m2
to 25 m2
depending upon
soil type,
topography,
stream size and
crop.
Ring basin flooding
• Special form of check basin flooding adapted for orchards
• Ring basin are formed for each or 2-3 trees
• Water is supplied to these basins through supply ditches
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Furrow irrigation
• Used for row crops. (cotton, maize, sugarcane, groundnut potatoes)
• Furrows are formed between crop rows. Water is applied in these
furrows
• Water infiltrates into soil and spreads laterally to wet the area
between the furrows
Furrow irrigation
• Dimension of furrows depend on the crop grown, equipment
used and soil type
• Furrows may vary from 8-30 cm deep and may be as much as
400 m long
• The land is wetted only along the furrows
• Used for crops which may damage when in contact with
water
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Furrow irrigation Advantages
• Water contacts only 1/5 to ½ of the land surface, thereby
reduce the puddling and crusting of the soil. Labour
requirement in land preparation can be reduced
• Evaporation losses are reduced
• Earlier cultivation is possible
• May be adopted over a wide range of slopes without the
erosion problems
• Suitable for crops that are injured by contact with water
Contour farming
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Contour farming
• It is followed in hilly areas having steep slope with quickly
falling contours.
• Area is divided into longitudinal curved plots, the bunds of
the plot following the contour
• These contour lines 🡪 water break 🡪 reduces the formation
of rills and gullies during times of heavy water run-off🡪
reduces soil erosion
• Field operations are carried along the slope rather than up
and down the hill
– The first contour1.2 to 1.5m vertically below the top of hill
Sub surface irrigation
• Water does not wet the soil
• Underground water nourishes the plant roots by capillary
action
Natural sub surface irrigation
• Achieved by natural process
without additional efforts
• Leakage from channels etc.
Artificial sub surface irrigation
• A system of open jointed
drains is artificially laid below
the soil
• Very costly and hence
practiced only at a small scale
in India
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Sub surface irrigation
Advantages
1. Minimum water requirement for raising crops
2. Minimum evaporation and deep percolation losses
3. No wastage of land
4. No interference to movement of farm machinery
5. Cultivation operations can be carried out without concern
for the irrigation period.
Drawbacks
1. Requires a special combination of natural conditions.
2. There is danger of water logging
3. Possibility of choking of the pipes lay underground.
4. High cost.
Sprinkler irrigation
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Sprinkler irrigation
• Conveys water to the field through pipes (aluminium or PVC)
under pressure with a system of nozzles.
• A kind of artificial rain
• Costly process, widely used in USA
• This system is designed to distribute the required depth of
water uniformly, which is not possible in surface irrigation.
• Water is applied at a rate less than the infiltration rate of
the soil hence the runoff from irrigation is avoided.
• Can be used for all types of soils and on different
topographies and slopes
More useful where
• Topography is irregular , where surface irrigation is not
possible
• Land gradient is steeper and soil is easily erodible
• Soil is excessive permeable or highly impermeable
• When the water table is high
• Where the seasonal water requirement is low
• Where water is scarce
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Sprinkler irrigation
Advantages Drawbacks
• Water saving of about 35-40% • High initial cost
compared to surface irrigation • Efficiency is affected by
wind
• Saving in fertilizers - distribution • Higher evaporation losses in
and avoids wastage. spraying water
• Suitable for undulating and • Not suitable for tall crops
slopping lands
like sugarcane
• Not suitable for heavy clay
• Reduces erosion soils
• Suitable for coarse textured soils • Poor quality water can not
(sandy soils) be used
• Drainage problems eliminated
• Saving in land
Drip irrigation
• Drip or trickle irrigation is one of the latest methods of
irrigation.
• It is suitable for water scarcity and salt affected soils.
• Water is applied in the root zone of the crop
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Components of a drip irrigation system
• Pump or overhead tank
• Main line : Delivers water to the sub-mains
• Sub-mains: Delivers water to the laterals
• Laterals and emitters attached to laterals: distribute water for irrigation.
• Regulator, filters, valves, water meter, fertilizer application components,
etc.
Sprinkler Irrigation
Advantages Drawbacks
• Water saving: Losses due to deep • High initial cost
percolation, surface runoff, • Drippers are
transmission, and evaporation losses susceptible to
are minimum blockage
• Uniform water distribution • Interferes with farm
• Application rates can be adjusted by operations and
movement of
using different size of drippers machineries
• Suitable for wide spaced row crops, • Frequent
particularly coconut and other maintenance
horticultural tree crops • Trees grown may
• Soil erosion is reduced develop shallow
• Better weed control confined root zones
resulting in poor
• Land saving anchorage
• Less labour cost
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Summary
• Types of irrigation
– Flow irrigation
• Perennial
• Inundation / flood
• Depending on the source
– Direct, storage and combined
– Lift irrigation
• Methods of irrigation
– Surface
• Flood irrigation
– Wild flooding
– Controlled flooding
» Free flooding, contour laterals, boarder strip, check basins, ring
basins
• Furrow irrigation
• Contour farming
– Subsurface
– Sprinkler
– Drip
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