India is an agricultural country. About seventy per cent of its people depend on agriculture. Watering is essential for the crops. Agriculture is not possible without water. We have to depend on rains for water for our fields, but we do not get rains throughout the year. India gets almost all of its rainfall during the rainy season from June to September. The rainfall is not uniform. Some parts get heavy rainfall. The rivers get flooded and damage the life, property and crops. Some parts get moderate rainfall and some parts are left without rainfall. The rainfall also varies from year to year. In some years we get heavy rainfall, while in some other we do not get sufficient rainfall.
We need regular watering for our crops. The watering of crops is known as irrigation. There are various means of irrigation used in our country.
Means of Irrigation
1. Tanks :
Rain water collects in the low lands in the form of tanks and ponds. This is perhaps the oldest means of irrigation in India. This means of irrigation is used in the Deccan Plateau and in the States of Andhra Pradesh, Karnataka and Tamil Nadu. The land is uneven and rocky. It can store water for irrigation. Huge tanks have been constructed for irrigating the land. About 12% of the agricultural land is being irrigated by tanks in India.
2. Wells :
Most of the rain water flows down the rivers and streams. Some of the water gets soaked by the soil. It goes on collecting on the hard rocky bed under the soil. This underground water is brought to the surface by wells and tube-wells. A large and deep hole is made in the earth's surface upto the water level. These are known as artesian wells. The water collects in the wells.
This water is used for drinking as well as for irrigating the land. This water is drawn out of the well by means of a pulley, wheel or lever. Various names have been given to the wells with these devices. Persian wheel was used for irrigating the fields for a long time. It is an old device now.
3. Tube-wells :
This is the means of irrigation of about 40% land in the plain areas. A deep bore is made in the earth's surface upto the water table. A pipe or a tube is fixed in this bore. An electric pump-set or a diesel pump-set is used to pump out water through this tube or pipe. It is known as a tube-well. This is the most commonly used means of irrigation in the Gangetic Plain or the Northern Fertile Plain. The underground water is available there because the land is even and soft. A bore hole can be made easily and electricity is available. Tube-wells are mostly used for irrigation in Punjab, Haryana, Uttar Pradesh, Bihar and West Bengal.
4. Canals :
Canals are a means of irrigation of almost 40% of agricultural land in India. The rivers in the Northern parts of India flow down the Himalayas and have water throughout the year. This water is taken through canals to irrigate the land in far away areas. Canals are used for irrigating the land in Punjab, Haryana, Delhi, Uttar Pradesh, Bihar and Northern - Rajasthan.
5. Dams :
Dams are huge and high walls, which are built across the rivers to hold water. The water of the river collects in the form of a lake, it is taken through canals to irrigate the fields when required. Such dams have been built across many of the rivers in Northern as well as Southern parts of India. The water in these dams is used to generate electricity. This electricity is then supplied to nearby places. Electricity generated from water is called Hydro-electricity.
Multipurpose Power Projects
There are some 600 projects big and small in India. Some of these projects serve more than one purpose. They control floods, store water for irrigation and generate hydro-electric power. The water of the dam forms a lake, where fish is reared. It is developed as a tourist resort and boating is done. Since they serve a number of purposes, they are known as the Multipurpose Power Projects. Some of the most important multipurpose projects are the Bhakra Nangal Project, Damodar Valley project, Hirakud Dam, Nagarjuna Sagar Dam, Krishna Sagar Dam, Farakka Barrage, Pong Dam, Thein Dam, Tungbhadra Project, Kosi Project, Sone Canal Project and the Rajasthan Canal Project.
BHAKRA NANGAL PROJECT :
This is the biggest multipurpose river valley project in India. It has been built across the river Sutlej at a place called Bhakra in Himachal Pradesh.
It is a joint project of Punjab, Haryana, Himachal Pradesh and Rajasthan costing about 175 crores. If is the highest dam in Asia and the second highest in the world. If is 226 metres high. The dam forms a huge lake called the Gobind Sagar behind it. If is the biggest man made lake in the world. Some power houses have been built on both sides of the dam which produce electricity.
At Nangal which is about 13 km. downstream from Bhakra Dam, a 29 metre high barrage has been built. It is called the Nangal Dam. It supplies water to Bhakra Canal, which carries water to Punjab, Haryana and Rajasthan. This canal is about 1100 km. long and the length of its distributaries is about 3000 km.
This dam has been built across the river Mahanadi. It is the longest dam in the world. It has been built for the prosperity of Orissa. It controls floods, supplies water for irrigation and generates hydro-electric power.
DAMODAR VALLEY PROJECT
Damodar was the most- turbulent river in Bihar. It caused great havoc through floods in Bihar. A number of dams have been built across the tributaries of this river which control floods, produce electricity and supply water for irrigation to Bihar and West Bengal.
Tungbhadra is a tributary of river Krishna. A dam has been built across Tungbhadra. If produces electricity and stores water for irrigation of land in Karnataka and Andhra Pradesh.
River Kosi is a tributary of the Ganga. The Kosi Project across the river Kosi, benefits Nepal and Bihar. Some environmental scientists and social workers are protesting against the construction of new dams. They fear that the construction of dams will disturb the environmental balance. A large area of the land under the forests and a large tract of fertile land along with villages and towns will be submerged in water. This will add to the miseries of the people living in those areas. Activists like Sunderlal Bahuguna and Medha Patekar are protesting against the construction of Tehri Dam and Narmada Project.