CHAPTER-6 WATER RESOURCES Topic-1 Sources of Water and Need for Conservation Concepts Covered  Watershed

Management  Aquifer  Percolation Pits  Surface Runoff Harvesting  Rooftop Rainwater Harvesting  Regional Names of
Rainwater Harvesting Systems

*Surface Water : Water that is available on land in form of Rivers, Oceans, Seas, Lakes and Ponds.
*Ground Water : Underground water that seeps into soil and is located in large aquifers under the ground.
*Industrialisation : Process by which an economy is transformed from agriculture to manufacturing goods with help of
machines in factories thus replacing manual labour by mechanized mass production.
*Urbanisation : Growth in number of people living in town and cities.
*Rainwater harvesting : It is a technique through which rainwater is collected from surfaces, filtering it and then storing it for
future use.
* The activity of collecting rainwater directly or recharging it into the ground to improve groundwater storage in the aquifer is
called Rainwater Harvesting.

Rainwater harvesting is the method of collecting rainwater for use before it reaches the ground. Generally, rainwater is
collected from the rooftop through pipes and stored in underground storage structures.

A well is a small hole dug in the surface of the Earth to obtain water from subsoil for irrigational and other purposes. It is a
traditional method of irrigation.

Wells are usually found in regions having a high groundwater table.

Elements of Rainwater Harvesting:

Catchment: Catchment is an area or a surface which receives direct rainwater.

Conduits: The pipelines or drains through which rainwater

Rainwater Harvesting is carried from the catchment to the water harvesting system are known as conduits.

Storage Facility: Rainwater can be stored in storage containers of RCC and masonry or in plastic water tanks.

Recharge Facility: Rainwater harvesting also recharges the groundwater aquifers.

Borewell  Tube-wells are used extensively in UP and Bihar and are very popular

*Watershed Management : It refers to the efficient management and conservation of both the surface and groundwater
resources.
*Aquifer : An underground layer of permeable rock, sediment or soil that yields water.
*Percolation Pits : It is used to collect rain water by percolation through the bottom or sides of the pits into surrounding soils.
*Surface runoff harvesting : System of catching and conserving rainwater where it falls that includes both natural and man-
made surface for its eventual reuse.
*Rooftop rainwater harvesting : It is the technique through which rain water is captured from the Roof catchments and stored
in Reservoirs.
*Irrigation : It is the supply of water to the plants through artificial methods from Wells, Tanks, Tube-wells, Canals, etc.
*Irrigation : The process of artificial application of water from canals, wells, tube wells, lakes etc.; to the soil for growing crops.
*Well : A pit or a hole created in the ground by digging, boring or drilling to access groundwater. It is drawn by a pump or by a
pulley.
*Persian Wheel Method : It is a mechanical water lifting device operated by draught animals like bullocks, buffaloes or camels.
*Tube-well : Tube-wells are deeper wells from where the water is lifted from a great depth of 20-30 m by the use of power
pumps.
*Inundation Canals : These are those canals which are taken out directly from the rivers without any regulating systems like
barrage or dam.
*Perennial Canals : These are those Canals which taken off from Perennial Rivers by Constructing a Dam or a Barrage across
the River.
*Drip Irrigation : It supplies the water to the roots of the plants slowly through pipes, valves, tubing, etc. and thus saves water
and fertilizer.
*Sprinkler Irrigation : It is a method by which water is supplied to the plants uniformly through a nozzle fitted in a pipe.
*Our Earth is surrounded by water from all sides but only about 0.03% of water is available to us as Freshwater in Rivers, Lakes
and Streams.
*About 97% water supply is from the Oceans and Seas and due to high salt content water is unfit for drinking and for
agricultural purposes.
*Sources of Fresh Water : (i) Surface Water (ii) Ground Water (iii) Rain Water
*Surface Water : Water that collects on the surface of the earth such as Oceans, Seas, Lakes, Rivers, Streams etc
*Ground Water : Water from rainfall that collects or flows beneath the Earth’s surface, sinks into the soil, filling the porous
cracks and spaces in soil, sediment and rocks. *Groundwater constitutes about 0.66% of usable water on the Earth.
*Water is the most essential element on earth. Life is impossible without it.
*The Increasing Population, Industrialization, Urbanisation and Agricultural Irrigation, have reduced the per capita availability
of water.
 Andhra Pradesh and Telangana are two states where tank irrigation and well irrigation is practised.
 Two methods of drawing water from the well are Persian wheel or Rehat and Moat.

*We need to Conserve Water due to the following reasons : (i) High demand of water due to Increasing Population is leading
to the lowering of the ground water levels. (ii) Rainfall in India is seasonal, erratic and unreliable thus, the farmers cannot
wholly depend on rain. (iii) More than 90% of water is utilized for irrigation. (iv) The Industries also utilizes a lot of water and
pollute it too. (v) A large amount of ground water like Lakes, Rivers, Streams, etc. are polluted which cannot be used without its
proper treatment. (vi) Scanty rainfall affects the growth of vegetation which results in drought and lowering of ground water
levels. (vii) Water is essential for generating Hydro-electric power.
*In order to overcome the shortage of water due to its increasing demands, we need to manage our water resources.
*A number of practices have been initiated and measures have been adopted to conserve water effectively.
*Some of these effective measures are- Rainwater Harvesting, Watershed Management, Water Saving Technologies, Recycling
of Water and Prevention of Water Pollution.
*Rainwater harvesting is a technique through which rainwater is collected from surfaces on which rain falls, filtering it and then
storing it for future use.
Rainwater harvesting is done by
 Storing rainwater and later using it in dry season - Harvesting of rainwater is done by storing it in tanks, ponds and
Dams. The stored water is used directly for irrigation and other domestic purposes.
 Recharging of groundwater - It is done by Rooftop rainwater Harvesting Method. Rainwater can be collected over the
rooftops and can be channelized through small PVC pipes into the underground pits, sump, wells or borewells.

*In other words, it is a technique of increasing the recharge of ground water by capturing and storing Rain water.
*It includes activities that are aimed at : (i) Harvesting surface and groundwater. (ii) Prevention of losses through evaporation
and seepage. (iii) Other techniques aimed at conservation and efficient utilization of limited water endowment.
*Rain water harvesting has become a necessity and we need to understand its value by making optimum use of rainwater
where it falls.
*The main objective of rainwater harvesting is to make water available for future use and to avoid flooding of roads.
*Water harvesting has many advantages like: (i) No land is wasted for storage purpose (ii) No population displacement is
required (iii) Ground water is not directly exposed to evaporation and pollution increases the productivity of aquifer (iv)
Reduces soil erosion (v) Recharges Groundwater resource
*In olden days there was different water harvesting mechanisms carried out in different regions of the country. They were (i)
Surface Runoff Harvesting (ii) Rooftop Rainwater Harvesting
The advantages of rooftop rainwater harvesting are:
 Utilization of rainwater to its maximum
 Easy and cost effective technique
 Recharges groundwater
 Avoids wastage of water due to run off

*In olden days in different parts of the country, rainwater storing mechanisms were known by different names. They were
called Water Harvesting in Western Himalayas- KUL / GUL. Kul in Western Himalayas, Zing in Ladakh, Baolis in the Gangetic
Plains, Johads in Central India and Rajasthan, Surangam in Western Ghats, Korambu in the Eastern Ghats and Bhandaras in
Deccan Plateau.
*Two states which suffer periodically from drought are Rajasthan and Gujarat. Rajasthan and Gujarat receive scanty rainfall
because the monsoon winds have very less moisture left by the time they reach there. Also, the position of Aravalis direct the
winds towards punjab.
 *Watershed Management refers to the efficient management and conservation of both the surface and groundwater
resources.
*It includes prevention of runoff as well as storage and recharge of groundwater by various methods like percolation pits,
recharge wells, borewells, dug wells, etc.
*The elements of Water Harvesting mechanisms are as follows : (i) Catchments : The catchment of a water harvesting system
is the surface drainage which collects rainfall.
(ii) Conduits : These are the pipelines or drains that carry rainwater from the catchment or rooftop area to the harvesting
system. (iii) Storage Facility : Rainwater can be stored in any available storage container like, Masonry or Plastic tanks, RCC
(Reinforced Cement Concrete), etc. (iv) Recharge Facility : Rainwater can be used to recharge groundwater aquifers through
any suitable structures like Dug wells, Borewells, Recharge Trenches and Recharge Pits.
Why is irrigation necessary for a country like India?
Irrigation is necessary for a country like India because of following reasons:
Monsoon is seasonal and rainfall is erratic, sporadic and unevenly distributed.
Irrigation is required to grow crops throughout the year as rainfall is seasonal.
Some crops like paddy, sugarcane and jute need more water which has to be supplied through irrigation.
Commercialization of agriculture and the pressure of growing population.
With proper irrigation, some crops like rice and wheat can have two growing seasons in a year.

Persian Wheel Method: It is a water-lifting device which has a partly submerged vertical wheel with buckets attached to the
rim. Animals such as buffaloes and camels are used to rotate the wheel. As they rotate the wheel, the buckets are filled, and
water is then emptied into a trough above which carries water to fields. Lever Method: It is an economical and efficient
method of lifting water from wells. It is widely practised in Bihar and Andhra Pradesh. Inclined Plane Method: This method is
also known as mhote. In this method, a pair of bullocks is used to lift water from wells.
Topic-2 Importance and Methods of Irrigation Concepts Covered  Persian-wheel Method  Wells  Tube-Well Irrigation 
Inundation Canals  Perennial Canals  Drip Irrigation  Sprinkler Irrigation

*Irrigation refers to the process by which a controlled amount of water is artificially supplied to the plants at regular intervals
to help in the production of crops.
*In other words, Irrigation is the supply of water to the plants through artificial means such as wells, tanks, tube wells, canals,
from the sources of water like surface water or ground water.
Despite big river projects, irrigation through groundwater has still been growing in popularity because of following reasons:

 Irrigation projects are still not available in many remote areas of India whereas
 ground water is available in most parts.
 It is easy and cheap to harvest ground water.
 The erratic and variable rainfall has made ground water more popular.
 Advantages of Surface water resource:

The surface water is easily available for drinking and irrigation.

The surface water is used for thermoelectric power.
 Advantages of Groundwater resource:

The ground water is reliable source of water for drinking.

It is not wasted by evaporation.

Water Resources in India India is a land of many rivers, lakes, lagoons and ponds. These resources account for 4% of the world’s
water resources. In India, water is mainly used for drinking, irrigation, household and industrial purposes. Currently, about 92%
of water is used for agricultural purposes, 2% in industries and the remaining 6% is used for drinking and household purposes.
The process of watering agricultural plants through artificial means such as tanks, wells and canals is known as irrigation.
Agriculture in India is largely dependent on rainfall to sustain crop production. To reduce the dependence of agriculture on
rainfall, many tanks, wells and canals have been laid. Several multipurpose dams have also been constructed. Emphasis has
been laid on building artificial means of irrigation because of the following reasons:

*Agriculture is the backbone of Indian economy and about 70% people are engaged in it.
*92% of water is utilized for irrigating the agricultural fields.
*Though rainfall is still an important source of water for a successful farming yet these artificial means of irrigation support
farming to a large extent.
*Irrigation is the most essential requirement for the development of agriculture in India due to the following reasons : (i)
Uncertainty of rainfall. (ii) Uneven distribution of rainfall. (iii) Requirement of different quantities of water for various crops for
their growth. (iv) Dependence of crops on rainfall. (v) Utilization of river water effectively. (vi) To increase or maximise
production.
*There are various methods of irrigation- Traditional and Modern methods.
The different methods of irrigation are classified into two groups:
Primitive Methods - Canal irrigation, Tank irrigation, Wells
Modern Methods- Sprinkler Irrigation,Drip Irrigation, Bamboo Irrigation

*Traditional methods of irrigation includes wells, tanks and inundation canals and modern methods include tube wells,
perennial canals, drip irrigation, spray irrigation, furrow irrigation and sprinkler irrigation.
. Well irrigation is the oldest method of irrigation. A well is a hole, dug in the ground to obtain the underground water. It is
generally carried out in the places where the soil is soft and easy to dig.
*Well irrigation is practised in the states of Uttar Pradesh, Punjab, Haryana, Bihar, Goa, Gujarat, Rajasthan, Maharashtra,
Madhya Pradesh, Andhra Pradesh, Karnataka and Tamil Nadu.
*There are different methods of lifting water from the wells for irrigation in India. They are : (i) Persian Wheel Method. (ii)
Lever Method. (iii) Inclined Method. Iv) Table Wells: In this method, power-driven pumps are used to lift water from tube wells
from depths below 15 m. *There are many advantages and disadvantages of Well Irrigation.
Advantages of Using Wells  They can be dug at very low costs and hence can be used even by poor farmers.  Oxen which are
used for ploughing the land can also be used for drawing water from wells.  Pumps and tube wells can be used for lifting
water from great depths. Disadvantages of Well Irrigation  It is difficult to dig wells in the hilly regions of the north and stony
areas of the peninsula.  Wells can dry up because of the lowering of the water table.  Use of electricity and diesel to operate
tube wells makes irrigating fields expensive.
*Advantages of Well Irrigation : (i) Simplest and cheapest method. (ii) Can be dug anywhere where the soil is soft. (iii) Oxen
kept for ploughing of field can be utilized for drawing water from the wheel at no extra cost. (iv) By using pumps and tube
wells, water can be lifted from great depths.
*Disadvantages of Well Irrigation: (i) It is difficult to dig wells in the hilly regions and in the rocky areas of Southern Peninsula.
(ii) Due to uneven distribution of underground water resources in different areas, wells do not function effectively. (iii) Owing
to excessive withdrawal of underground water and lowering of water table, the conventional wells dry up.
*Tube wells are deeper wells from where the water is lifted from a great depth of 20 m - 30 m by using power pumps.
*The tube wells can be drilled in places which have the following conditions : (i) Availability of plenty of water. (ii) Soft soil,
level land and fertile area. (iii) Availability of cheap electricity at a regular basis to run tube wells.
•Of the two types of wells, tube wells are best because they can irrigate larger area and they occupy less area as compared to
surface wells. They are also helpful in drought affected areas.
Tanks A tank is an artificial reservoir built across a stream to impound water. Water from the tank is then carried to the fields
through narrow channels. Tanks are used for irrigation in peninsular India including Maharashtra and Gujarat. Tanks are
extensively used in Deccan because of the following reasons:  The Deccan has many natural depressions where tanks can be
easily built.  The rivers of the region are not perennial and become dry during the summer.  Wells cannot be dug in the
stony regions of the Deccan. Tanks however can be easily built by making small dams of stones in the depressions where
rainwater collects. Tank irrigation is largely practised in Andhra Pradesh, Tamil Nadu, West Bengal, south Rajasthan and south
Bihar.
*Advantages of Tube Well Irrigation : (i) It is able to irrigate a larger agricultural land. (ii) Large amount of underground water is
easily available. (iii) It is reliable during dry season when the surface water dries up since the tube well is drilled deeper up to
the permanent water table. (iv) A good amount of water can be pulled out in a short period of time. (v) They have played
important role in the Green Revolution.
*Disadvantages of Tube Well Irrigation : (i) Irrigation is not possible if the groundwater is brackish. (ii) It requires cheap and cost
effective power which is not available in most of the states. (iii) Irrigation is not possible if the underground water level is low.
(iv) Excessive use of tube well leads to lowering of groundwater level.
Advantages of Tank Irrigation  Tank irrigation is useful in Deccan regions where rainfall is seasonal and uncertain.  In the
rocky terrain of the Deccan Plateau, it is difficult to build wells and canals. In such regions, tanks are an important source of
irrigation.  Rainwater could be stored in the tanks which otherwise flow out and get wasted. This water is then used for
irrigation. Disadvantages of Tank Irrigation  Tanks can easily get silted up. Thus, regular desilting of tanks is required.  In case
of failure of rains, tanks also remain dry and hence are not a dependable source of irrigation.  Because of large area coverage
and shallow depth, water from tanks either evaporates or sinks underground.  Tanks can use a large infertile area which
otherwise could be used for growing crops.  The lifting of water from tanks and bringing it to the fields is a strenuous and
costly task.
For an Indian farmer state two advantages that well irrigation has over canal irrigation.
 Well irrigation is generally found in the alluvial plains where they can be easily dug because of the soft nature of the soil.  In
India, well irrigation is generally practised in Uttar Pradesh, Goa, Punjab, Haryana, Bihar, Rajasthan, Gujarat, Maharashtra,
Andhra Pradesh, Karnataka and Tamil Nadu.
  Well is simplest and cheapest source of irrigation and the poor Indian farmer can easily afford it.
 Well is an independent source of irrigation and can be used as and when the necessity arises. Canal irrigation, on the
other hand, is controlled by other agencies and cannot be used at will.
Reasons why tube well irrigation is more important in northern India than in southern India.
 Tube well irrigation is more important in northern India than in southern India because:
 The land in southern India is rocky while the land in norther India is softer, which makes it easy and cheap to dig tube
wells.
 The southern India has other water sources like sea, tanks, ordinary wells etc.
Tank irrigation is more popular in southern India because of following two reasons:
 Most of the area of peninsular India is uneven with many natural depressions where the tanks can be built.
 The Deccan plateau consists of underlying hard rocks which are impervious or non-porous. These rocks do not allow
the water to seep through.
 Drip irrigation A plastic tube which has small holes through which water keeps on dripping
 Bamboo irrigation  An ancient irrigation system in North East part of India.

*Tube well irrigation is mainly prevalent in the states of Punjab, Haryana, Uttar Pradesh, Bihar, West Bengal, Rajasthan,
Madhya Pradesh and Gujarat. II. Canal is an important and effective method of irrigation in India.
The two types of canal irrigation are Inundation canal and Perennial canal. Out of these, Perennial canal is better because it
provides water throughout the year while Inundation canal provides water only at the time of floods.
*Canal irrigation is mainly concentrated in Uttar Pradesh, Punjab and Haryana.
*Since digging is difficult in the rocky and uneven surfaces of land, canals are practically absent in the Southern Peninsular
region.
*There are two types of Canals in India : (i) Inundation Canal (ii) Perennial Canal
*Inundation Canals are those Canals which are taken out directly from the rivers without any regulating systems like barrage or
dam.
*This type of canal provides water for irrigation only during the rainy season and at times of flood.
*Since the level of water drops after the rainy season is over, the canal dries up and thus it has limited use.
*Perennial Canals are those Canals which are taken off from perennial rivers by constructing a dam or a barrage across the
river.
*These Canals help to irrigate large areas and can draw water throughout the year.
*Today in India most of the canals are Perennial.
 Canal irrigation leads to the ground around it becoming unproductive because
 due to waterlogging the capacity of the soil to absorb water decreases and the water which collects can ruin the crop
 percolation of water through canal can lead to swamps
 problem of salt effervescence due to over-flooding of the fields make the soil unsuitable for farming

*Canal irrigation is practiced in Uttar Pradesh, Punjab, Haryana, Bihar, Madhya Pradesh, Rajasthan, Andhra Pradesh.
*Uttar Pradesh has constructed a large number of canals to irrigate around 3,091 thousand hectares of land which is about
30.91% of the total canal irrigated area of the country.
*The important canals of Uttar Pradesh are Upper Ganga Canal, Lower Ganga Canal, Sharda Canal, Eastern Yamuna Canal, Agra
Canal and Betwa Canal.
*The important canals in Punjab are Upper Bari Doab Canal, Sirhind Canal, Bhakra Canal, Bist Doab Canal. , Makhu Canal

*In Haryana, the Western Yamuna Canal, Bhakra Canal, Jui Canal and Gurgaon Canal are the main canals.
*The important canals of Rajasthan are Indira Gandhi Canal, Gang or Bikaner Canal and Chambal Canal Projects.
Canals Canals are also an important means of irrigation in India. There are two main types of canals. These are Inundation
Canals: These are long canals directly taken off from large rivers. They receive water when the river is high enough and
especially when in flood. Thus, these canals have limited use only.
Perennial Canals: These canals are taken out from the perennial rivers by constructing small dams and barrages to regulate the
flow of rivers. Most canals in India are perennial. Some important canals in India are Upper Bari Doab, Bist Doab, Sirhind,
Bhakra and Western Yamuna Canals in Punjab and Haryana; the Indira Gandhi Canal and Bikaner Canal in Rajasthan; Eastern
Yamuna Canal, Sharda Canal, Ramganga Canal and Betwa Canal in Uttar Pradesh; and Damodar Canal and Mayurakhi Canal in
West Bengal.
In south India, canals are extensively used for irrigation. Nagarjunasagar and Tungabhadra projects are major canals in the
south. One-third of the net irrigated area in Tamil Nadu is under canal irrigation. The state of Mizoram is solely dependent on
canals for irrigation.
Advantages of Canal Irrigation  Canals irrigate fields in regions which get scanty rainfall.  In dry regions of Rajasthan, canals
irrigate fields which are yielding good agricultural harvests.  Canals have irrigated major parts of Punjab and Haryana. These
two states have become the nucleus of the Green Revolution.  Tamil Nadu gets rainfall during winters. Canals irrigate the
fields during summer and make up for the lack of rainfall.
Disadvantages of Canal Irrigation  In canal irrigation, where the water table is only few feet below the ground, the alkaline
salts may come to the surface, mix with the soil and make it unproductive.  Because of waterlogging of canals, the capacity of
the soil to absorb water decreases which can damage the crops in the absence of a proper drainage system.
Major Drawbacks of Conventional Methods of Irrigation  In the agricultural fields, about 10–15% of land is used for preparing
water channels, decreasing the effective area of cultivation.  In tanks and canals, owing to the evaporation of water, the soil
may silt.  The fields in the low-lying areas always get excess water resulting in waterlogging and subsequently the
accumulation of salt which damages the quality of soil.  In the conventional system of irrigation, a large quantity of water is
not properly used and gets wasted.
*Advantages of Canal Irrigation : (i) The perennial canals provide constant supply of water and save the crops from drought
situations. (ii) Canal irrigation has proved to be a boon to the sandy areas of Rajasthan which are yielding good agricultural
crops. (iii) Canal irrigation has converted Punjab and Haryana into ‘the Granary of the country’. (iv) Canals carry a lot of
sediment brought down by the rivers which get deposited in the agricultural fields and add to the fertility of the soil. (v)
Although the initial investment for constructing a canal is high but it is quite cheap in the long run.
*Disadvantages of Canal Irrigation : (i) During rainy season, many canals overflow and flood the already cultivated areas. (ii) In
areas where the water is excessively flowing in fields, it raises the ground water level and results in bringing the alkaline salts to
the surface, thereby making the field unfit for agriculture or unproductive. (iii) Due to waterlogging, the capacity of soil to
absorb water reduces and thus ruins the standing crops, stored grains, etc. (iv) Canal irrigation is suitable mainly in plain areas.
III. Tank Irrigation comprises an important source of irrigation mainly in the southern part of the country.
*Tank Irrigation is one of the oldest irrigation systems in India.
*It is mainly carried out in the rocky plateau region of South India where the rainfall is highly seasonal and uneven.
*Tank Irrigation is practiced in Andhra Pradesh, Telangana, Tamil Nadu, Maharashtra, Gujarat, Madhya Pradesh, etc.
 Tanks are most widely used in peninsular India because natural pits and depressions are easily available in this area
and the rocky base of tanks does not allow wastage of water due to percolation.

*Tank irrigation is mainly prevalent in South India due to the following reasons : (i) Due to hard rocks, non-porous and rocky
surface the water doesn’t penetrate through the layers of the soil. There is no loss of water through seepage. (ii) The Deccan
terrain is uneven with many natural depressions which facilitate the construction of tanks
*Advantages of Tank Irrigation: (i) It is inexpensive as there are mostly natural depressions. (ii) It is highly beneficial in the
uneven rocky plateau of Deccan since rainfall is seasonal. (iii) Since wells and tube wells cannot be dug in the rocky surface of
the Deccan Plateau, tanks are easily constructed.
*Disadvantages of Tank Irrigation: (i) In the absence of rainwater during dry season, the tanks become dry and fail to provide
water for irrigation. (ii) Due to deposition of sediments, the tanks get silted up soon and de-silting is necessary for maintaining
the storing capacity of tank. (iii) Tanks occupy large fertile areas which otherwise could be used for agricultural purposes. (iv)
Since tanks are very extensive and shallow, huge quantities of stored water go waste as it gets evaporated or sinks
underground.

Advantages of tank irrigation are:

 Tank irrigation is cheaper and is prevalent in Deccan plateau where natural pits and depressions are found.
 As the water is collected and used in dry season, it uses the water table of the surrounding region.
 It is difficult to build canals in the Deccan plateau regions.
 The tank water is used for domestic purposes in villages.
 In the absence of perennial rivers and canals, tanks provide a source of water during the dry season.
Disadvantages of tank irrigation are:
 Since tanks are shallow, large amount of water is wasted through evaporation.
 Tanks are non-perennial and dry up in summer. Considering this and the large area they occupy, they become costly in
comparison to wells and tube wells.
 Tanks use up large areas of land which could be used for agriculture.

Modern Methods of Irrigation

Furrow Irrigation: It is a type of surface irrigation in which furrows or trenches are dug between rows of crops in the field
instead of distributing water throughout the fields. It is useful in areas where water is easily available.
Spray Irrigation: In spray irrigation, water is released in an agricultural field by spray guns.
In spray irrigation, water is used efficiently in irrigating the fields. One limitation of this method is that it is expensive as it
requires complex and sophisticated machinery. Further, plants may suffer from many diseases because of overwatering of
fields.
Furrow Irrigation
Drip Irrigation: In this system of irrigation, water is given directly to the crops through perforated pipes which are placed
between rows of crops. This method reduces the rate of evaporation and helps in conserving water. This is the most advanced
and efficient means of irrigation. We need to conserve water as the population is growing at an extremely fast pace.
Overexploitation of underground water has resulted in lowering the water table. Further, the demand of water for domestic
and industrial use has also increased. Many water bodies such as rivers, lakes and tanks have been polluted and hence cannot
be used for basic purposes.

*The Conventional System of Irrigation or the Traditional Method of Irrigation has a number of disadvantages. They are : (i)
These methods are not dependable as rainfall is seasonal. (ii) Waterlogging is caused in the low-lying agricultural fields due to
the flowing of excess water which damage the crops and gives poor yield. (iii) Due to accumulation of salts in arid and semi-
arid regions of India, large tract of lands are left barren and cannot be utilized for cultivation.
*Modern methods of/irrigation are efficient and supply water to the fields more uniformly as compared to the Traditional
Methods of Irrigation.
*The important modern methods of Irrigation are : (i) Drip Irrigation : This method is considered to be the most efficient and
advanced system of irrigation. It supplies the water to the roots of the plants slowly through pipes, valves, tubing, etc. and thus
saves water and fertilizer. This helps in the reduction of evaporation. (ii) Sprinkler Irrigation : It is a method by which water is
supplied to the plants uniformly through a nozzle fitted in a pipe. It is widely used in the arid areas as it checks and controls the
wastage of water through evaporation and seepage.
One advantage of this type of irrigation is that there is no loss of water through evaporation and seepage and one
disadvantage is that it is expensive and can water only a small area. (iii) Furrow Irrigation : It is a type of surface irrigation in
which furrows are dug between the rows of the crops and water is evenly distributed to the entire field. It is one of the oldest
methods of irrigation and is cheap. (iv) Spray Irrigation : In this type of irrigation, water is shot from high pressure sprayers onto
the crops through a long hose pipe. It is expensive but utilizes water more efficiently. Since it is sprayed so a good amount of
water gets evaporated.
Inundation canals are being converted to perennial canals because: With Inundation canals, there is uncertainty of water
supply. They are useful only during floods. Only low-land areas can be irrigated.

Recharging Groundwater Aquifers

Some commonly used water recharging methods are digging of  Bore wells  Recharge pits  Percolation pits  Recharge
trenches

 Irrigation in India is indispensable for sustained agricultural development because of India experiences tropical
monsoon climate which is unevenly distributed, unreliable and erratic in nature
 The perennial canals can be built in the areas of low level relief with deep fertile soil
 A tank can be constructed in the area of undulating relief,underlying hard rocks&natural depressions.
 The tank irrigation is practiced mostly in TN
 A tube well is a borewell
 The given type of modern irrigation is useful for arid region is sprinkler irrigation


 Irrigation by canals is more suitable in Northern India because the surface of the northern plain is flat with soft soil
 Rainwater harvesting is useful for recharging ground water

Two problems faced by India regarding irrigation are:

 The rainfall is highly uneven and is mostly received in four months. Most of the rivers are seasonal.The irrigation
projects are still not available in most of the parts of India.
  The objectives of National Water Policy are: To analyze the existing situation of water & To propose a framework for
creation of a system of laws and institutions for water management. & To recycle and treat waste water
 River Damodar is called "river of sorrow".  River Damodar was earlier called "river of sorrow" because of its ravaging
floods in the plains of West Bengal which caused heavy losses and destruction. With the construction of several dams
the floods of Damodar river have been greatly reduced but even now the floods sometimes affect the lower Damodar
Valley.

 Irrigation by canals is more suitable in northern India as compared to the south  Canal irrigation is more suitable in
northern India as compared to the south because the northern rivers are perennial and can supply water to canals
throughout the year but the rivers of south India are seasonal and therefore, canals are of no use in dry season.

 Tank irrigation is used in peninsular India because The peninsular India has natural depressions which act as natural
tanks and the rocky surface does not allow percolation of water. Therefore, tank irrigation is used in peninsular India.

Advantages of Sprinkler Irrigation are: This type of irrigation does not involve any wastage of water by seepage or evaporation
as water is supplied through pipes and not exposed to the sun. This is the best method for conservation of water. It is best
suited for arid and semi-arid regions.

Water management is easier than surface irrigation system.

Higher application efficiency.
Frequent application is possible.
Does not interfere with the cultivation.
Easy mechanization and automation.
Chemical and fertilizer application can easily be used with sprinkler system.
Disadvantages of Sprinkler Irrigation:
High initial cost.
High operating cost.
Water application efficiency under sprinkler irrigation is strongly affected by direction of the wind.
Some crops are sensitive and may suffer leaf scorch because of salt deposited on the leaves after the water evaporates.
High maintenance requirements as constant and meticulous maintenance of sprinkler system is very important.
Saline water may cause problems.
Water must be free from sand debris and salt.

Why is it necessary to conserve water?

It is necessary to conserve water because

There is uncertainty in rainfall and distribution of water is uneven.
There is over-exploitation and excessive use of water.
Contamination of water due to pollution, use of pesticides and fertilizer.
There is scarcity of water due to large and growing population.
Increasing industrialization and rapid urbanization is exerting pressure on water resources.

 Name the type of irrigation  Drip Irrigation

 Advantages of Drip Irrigation are:

 Fertilizer and nutrient loss is minimized due to localized and reduced leaching.
 Water application efficiency is high if managed correctly.
 Field levelling is not necessary.
 Recycled or non-potable water can easily be used.
  Moisture within the root zone can be maintained at field capacity.
 Soil erosion is less.
 Water distribution is highly uniform.
 Labour cost is less.
 Variation in supply can be regulated by regulating the valves and drippers.
 Fertilization can be included with minimum waste of fertilizers.
 Usually operated at low pressure thereby reducing energy costs.

 Question 13
 What is the difference between surface water resource and groundwater resource? State two advantages of each.


 S.
 Surface water resource  Groundwater resource
No.

 Groundwater is the part of

 Surface water is available on the
rainwater that seeps into the
 1. surface of earth in the form of
ground through the cracks and
rivers, lakes, ponds and canals.
crevices.

 Ground water is available

 Surface water resources are mostly
 2. throughout the year and is
seasonal.
recharged every monsoon.

 3.  Can be used directly  Requires pumping

 4.  Usually contaminated  Usually fit for drinking

 Question 16
 Differentiate between inundation canal and perennial canal.
 Answer

 S.
 Inundation canal  Perennial canal
No.

 Inundation canals are taken out

 Perennial canals are taken
from the rivers without any
 1. out from the rivers with
regulating systems like weirs and
regulating system.
barrages.

 Inundation canals are useful only  Perennial canals supply

 2.
during floods. water throughout the year.

 They are expensive to

 3.  They are easy and cheap to built.
construct.

Mechanism
of Rainwater Harvesting  Rainwater on the rooftop is first collected using a PVC pipe. Water is then filtered by using sand and
bricks.  Water is taken down to either a sump (a hollow structure or a depression where liquids collect) for immediate use or
is taken to a well or any other structure which is dug on the premises.  Water from this well can be used later for domestic
consumption. It also recharges the water table.
The Central Pollution Control Board (CPCB) of India is a statutory organisation under the Ministry of Environment, Forests and
Climate Change in sep 1974