Water is the most precious resource for mankind. It determines the health, metabolism and survival of all living species.
Without water no life form can survive on the earth. Being essentially a water planet plenty of water is available on the earth and, hence, its reckless use is prevalent and scarcity is not correctly assessed. With growing population and increasing use of water for domestic, irrigation and industrial purposes the scientists are forewarning about a severe water crisis and famine in the future.
This needs proper survey and assessment of the water resources of a region or country and suitable measures for their scientific planning, management and conservation. The Government of India for the survey and balanced utilisation of water resources of the country and devising a water resource management policy has constituted an independent department of water resources.
There are two main sources of water resources: (a) surface water, and (b) ground water. Rivers are the principal source of surface water. According to K.L. Rao (1975) the total quantity of water annually carried by the rivers of the country is about 16, 45,000 million cum (by S.P. Das Gupta, 1989 as 18, 58,100 million cum).
It is also estimated by Rao (1975, p.217) that the utilis- able water of all the surface river systems and 75 per cent of the utilisable underground waters will be 1,000,000 million cum or a little over about half of the total water in India. Following table estimates the utilization of water in different sectors by 2000 A.D.
Source: Rao. K.L. (1975): India's Water Wealth
Another method to assess the water budget is to quantify the hydrological cycle as proposed by B.S. Nag and G.N. Kathapalia. The Chart depicts that out of 400 m ham of annual precipitation 180 m ham is available as surface flow, while 67 m ham is the total groundwater percolation. This may increase to 185 and 85 m ham respectively owing to better conservation methods by 2000 A.D. while reducing evaporation losses. The maxmum usable potential, thus, comes to 105 m ham. Of this only 9.5 per cent was being utilised in 1975. This utilization ratio is estimated to increase to 26% by 2000 A.D.
In water utilization the irrigation consuming 92 percent in 1974, comes on the top followed by the domestic and industrial consumption. Due to increasing use of water in power and industries (13%
and 3% respectively) the share of agriculture is likely to be slightly reduced (77%) by 2000 A.D. (Table 4.II)
According to one estimate the total ground water reserve at a depth of 300 m is estimated at 3700 m ham, almost ten times the annual rainfall. The recent survey shows that the peninsular region is supposed to store more ground water than earlier estimated.
The Central Ground Water Board (CG WB) estimates the annual exploitable potential at 42.3 m ham of which less than 1/4 is presently being exploited. In terms of exploitation of ground water potential Punjab comes on the top (93.85%), followed by Haryana (83.88%), Tamil Nadu (60.44), Rajasthan (50.63), Gujarat (41.45), Uttar Pradesh (37.67), Maharashtra (30.39), West Bengal (2.4.18), and Andhra Pradesh (23.64). States like Assam (4.48), Orissa (8.42), Madhya Pradesh (16.49) and Bihar (19.19) have not been able to utilise even 20 per cent of their total ground water potential.
Amongst the problems of surface water resources mention may be made of their highly fluctuating regime, uneven spatial distribution, and wastage during floods, reckless and unscientific utilization, pollution problems, river water disputes between different states and lack of suitable measures for conservation and planning.