Water Resources

The process of artificial application of water from canals, wells, tube wells, lakes etc.; to the soil for growing crops is called irrigation.

Irrigation is necessary for a country like India because of following reasons:

1. Monsoon is seasonal and rainfall is erratic, sporadic and unevenly distributed.
2. Irrigation is required to grow crops throughout the year as rainfall is seasonal.
3. Some crops like paddy, sugarcane and jute need more water which has to be supplied through irrigation.
4. Commercialization of agriculture and the pressure of growing population.
5. With proper irrigation, some crops like rice and wheat can have two growing seasons in a year.

The different methods of irrigation are classified into two groups:

1. Primitive Methods
   1. Canal irrigation
   2. Tank irrigation
   3. Wells
2. Modern Methods
   1. Sprinkler Irrigation
   2. Drip Irrigation
   3. Bamboo Irrigation

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.

Tank irrigation refers to irrigation in which water stored in artificially constructed tanks is used for irrigation. Tanks are constructed in areas of natural depression by building earthen embankments or masonry walls to collect water.

Advantages of tank irrigation are:

1. Tank irrigation is cheaper and is prevalent in Deccan plateau where natural pits and depressions are found.
2. As the water is collected and used in dry season, it uses the water table of the surrounding region.
3. It is difficult to build canals in the Deccan plateau regions.
4. The tank water is used for domestic purposes in villages.
5. In the absence of perennial rivers and canals, tanks provide a source of water during the dry season.

Disadvantages of tank irrigation are:

1. Since tanks are shallow, large amount of water is wasted through evaporation.
2. 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.
3. Tanks use up large areas of land which could be used for agriculture.

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.

Of the two types of wells, tube wells are 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.

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.

Despite big river projects, irrigation through groundwater has still been growing in popularity because of following reasons:

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

Two advantages that well irrigation has over canal irrigation for an Indian farmer are:

1. Well is simplest and cheapest source of irrigation and the poor Indian farmer can easily afford it.
2. 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.

Advantages of Surface water resource:

1. The surface water is easily available for drinking and irrigation.
2. The surface water is used for thermoelectric power.

Advantages of Groundwater resource:

1. The ground water is reliable source of water for drinking.
2. It is not wasted by evaporation.

Canal system in Uttar Pradesh are:

1. Ganga canal
2. East Yamuna canal

Canal system in Punjab are:

1. Sirhind Canal
2. Makhu Canal

Two problems faced by India regarding irrigation are:

1. The rainfall is highly uneven and is mostly received in four months. Most of the rivers are seasonal.
2. The irrigation projects are still not available in most of the parts of India.

Inundation canals are being converted to perennial canals because:

1. With Inundation canals, there is uncertainty of water supply. They are useful only during floods.
2. Only low-land areas can be irrigated.

Tube well irrigation is more important in northern India than in southern India because:

1. 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.
2. 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:

1. Most of the area of peninsular India is uneven with many natural depressions where the tanks can be built.
2. The Deccan plateau consists of underlying hard rocks which are impervious or non-porous. These rocks do not allow the water to seep through.

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.

The objectives of National Water Policy are:

1. To analyze the existing situation of water
2. To propose a framework for creation of a system of laws and institutions for water management
3. To recycle and treat waste water

The activity of collecting rainwater directly or recharging it into the ground to improve groundwater storage in the aquifer is called Rainwater Harvesting.

It is necessary to conserve water because

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

Rainwater harvesting is done by

1. 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.
2. 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.

The advantages of rooftop rainwater harvesting are:

1. Utilization of rainwater to its maximum
2. Easy and cost effective technique
3. Recharges groundwater
4. Avoids wastage of water due to run off

Tamil Nadu and Andhra Pradesh.

1. 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.
2. 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.
3. 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.

1. Drip irrigation
2. Bamboo irrigation
3. Borewell

Advantages of Sprinkler Irrigation are:

1. 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.
2. This is the best method for conservation of water.
3. It is best suited for arid and semi-arid regions.
4. Water management is easier than surface irrigation system.
5. Higher application efficiency.
6. Frequent application is possible.
7. Does not interfere with the cultivation.
8. Easy mechanization and automation.
9. Chemical and fertilizer application can easily be used with sprinkler system.

Disadvantages of Sprinkler Irrigation:

1. High initial cost.
2. High operating cost.
3. Water application efficiency under sprinkler irrigation is strongly affected by direction of the wind.
4. Some crops are sensitive and may suffer leaf scorch because of salt deposited on the leaves after the water evaporates.
5. High maintenance requirements as constant and meticulous maintenance of sprinkler system is very important.
6. Saline water may cause problems.
7. Water must be free from sand debris and salt.

The modern methods of Irrigation are

1. Sprinkler Irrigation
2. Drip Irrigation
3. Bamboo Irrigation

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

India experiences tropical monsoon climate which is unevenly distributed, unreliable and erratic in nature

low level relief with deep fertile soil

all the above

Tamil Nadu

borewell

sprinkler irrigation

the surface of the northern plain is flat with soft soil

all the above

recharging ground water