India has plenty of freshwater. The sub-continent receives most of its fresh water during monsoon months (almost 75%). Rest of the months is drier which necessitates the use of ground water or stored water during the dry spells.
The uneven distribution of rains in different months of the year is matched by its equally uneven distribution over different regions of the country. Parts of Rajasthan receive very little rains while there are places like Cherapunji which had the reputation of being the wettest place in the world.
(1) The Resource B ase:
India receives about 4,000 cubic kms of fresh water as precipitation every year. About 700 cubic kms of water thus received evaporate immediately and are lost to the atmosphere. About 2,150 cubic kms go to the soil whereas about 1,650 cubic kms are retained as soil moisture while about 500 cubic kms permeate through the soil surface to underground water deposits. Only 1,150 cubic kms of fresh water received annually are retained on land surface. Water resources in our country can be grouped as under:
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1. Surface Waters:
To 1,150 cubic kms of fresh water which appear as surface water may be added about 200 cubic kms of surface flow which comes from outside India. The surface flow is further enlarged by addition of about 450 cubic kms of fresh water from ground water flow while about 50 cubic kms are added as runoff from irrigated areas. The surface loses almost 50 cubic kms of its water which percolates down to the ground water deposits. The total surface flow per year is about 1,800 cubic kms which are distributed among a number of river basins.
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Distribution of surface flow in rivers of India.
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All quantities in Cubic Kilometres. (Source: Kathpalia 1983)
2. Ground Water:
The major portion of fresh water which goes to earth’s crust is retained by its upper layers as soil moisture (about 1,650 cubic kms). Only 500 cubic kms percolate down to the ground water deposits. A large amount of fresh water applied to agricultural fields (about 120 cubic kms) moves down to ground water table while about 50 cubic kms of surface flow also end up as ground water. Therefore, a total of about 670 cubic kms of fresh water enters the ground water annually. It is upto this amount that we can withdraw fresh water from our sub-surface deposits. Any withdrawal above this limit shall be detrimental to the resource base.
(2) Requirement of Fresh Water in India :
Like rest of the world, agriculture sector is the major consumer of fresh water in India. It is followed by domestic needs and requirement for live-stock management which taken together use about 13.5 cubic kms of fresh water. Thermal power generation sector is the next biggest consumer of fresh water which is followed closely by industries. It summarizes the approximate requirement of fresh water in India as estimated for the years 1974 A.D., 2000 A.D. and 2025 A.D.
Estimates of fresh water requirement in India.
|
Water needed for |
1974 |
2000 |
2025 |
|
|
1. |
Irrigation. |
350.0 |
630.0 |
770.0 |
|
2. |
Thermal power generation. |
11.0 |
60.0 |
160.0 |
|
3. |
Industries |
5.5 |
30.0 |
120.0 |
|
4. |
Domestic requirements |
8.8 |
26.6 |
39.0 |
|
5. |
Livestock management |
4.7 |
7.4 |
11.0 |
|
Total |
380.0 |
754.0 |
1100.0 |
All quantities in cubic kilometres (Source: Kathpalia 1983).
The approximate distribution of total annual fresh-water resources in India is summarised in Fig. 6.3. In 1974 A.D. we used about 380 cubic kms of water. It is interesting to note that nearly 65% of country’s water requirement was met with by surface waters which contributed about 250 cubic kms while ground water provided about 130 cubic kms of fresh waters.
By 2000 A.D. the total water requirement is expected to double itself while about 2025 A.D. we shall be requiring almost thrice as much water as we did in 1974 A.D. This extraordinary rise of demand for fresh water shall not be uniform in various sectors of our economy. In 2025 A.D. the requirement for irrigation water will be doubled whereas our domestic needs as well as water requirement for livestock management shall be about four times than those of 1974 A.D.
By the third decade of next century industrial sector in India shall require about 20 times and power-generation sector about 15 times more water than it did in 1974. A glance at Table 6.3 reveals that the utilizable surface flow in India amounts to about 700 cubic kms only. Our requirement shall exceed this amount by 2000 A.D. We shall have to bank more and more upon our ground water resources.
(3) Fresh Water Conservation in India:
India has a long history of water resource development and conservation. Due to concentration of major portion of precipitation during monsoon months (75%) much of the fresh water is lost as flood flows and during the remaining months scarcity of water develops. Ponds, tanks, embankments have been made since time immemorial to resolve the water crisis during the drier months. The Delhi Sultanate and the late Moghuls engaged in large-scale irrigation works in Northern India during 1350 to 1780 A.D. By-1900 A.D., irrigation facilities already covered an area of about 40 thousand sq. kms.
After independence as food problems plagued the Nation, huge irrigation projects were undertaken to raise agricultural productivity under a series of Five Year Plans. These projects involved an enormous amount of public money which was largely diverted to raise the surface storage capacity of our country and dig huge canals for irrigation purposes.
The Ministry of Water Resources, Govt. of India classifies various projects undertaken from| time to time under the following two major headings:
1. Minor surface irrigation sector.
2. Major and Medium irrigation sector
Minor surface irrigation sector (MSI) comprises of small projects which irrigate only 2,000 hectares each. Ground water irrigation sector is also placed under this category. This sector employs wells, tube wells, tanks, bunds, traditional lift irrigation etc. to provide water for agriculture purposes. As a matter of fact, Minor surface irrigation sector seems to be in a very poor shape,! However, because of its grouping with ground water irrigation sector which is almost doubly efficient and productive, the actual performance of MSI is masked from general observation.
Major and medium irrigation sector involves huge projects under which huge dams and bunds are constructed with a capacity to hold billions of cubic metres of water and to irrigate millions of hectares of land surface. These projects have enhanced country’s surface storage capacity to about 180 cubic kms and a net potential to irrigate about 78.1 million hectares of land.
Some of the major projects completed till date are : Damodar valley project, Bhakranangal dam, Kosi project, Hirakudl dam, Tungbhadra project, Nagarjuna sagar dam, Rehand dam etc. Along with these dams a network of canals has been dug to cater to the needs of farmers in drier regions. The energy of flowing water from these dams is used to generate hydro-electric power which is a completely pollution-free source of energy. By 1986-87 A.D. alone, India had developed an installed capacity to generate about 19,20,000 KW of hydro-electricity. These waters are also used to breed fishes.