The total estimated annual precipitation of India including snowfall is about 4000 billion cubic metre BCM.
A part of this recharges ground water,
a part of this is lost as evapo-transpiration
and the remaining flows a surface water.
The largest estimate of surface runoff water is 1869 BCM (1993) including annual recharge of ground water.
Out of 1869 BCM fresh water only 1123 BCM can be put to beneficial use because of many constraints.
Increase in population of India from 361 million in 1951 to 1130 million in 2007 is one of the major causes of the decrease of average per capita water availability from 5177 cum/year to 1654 cum / year.
The Falkenmark Water Stress Indicator is 1700 cum/year, so on an average India is water-stressed.
9 out of 20 river basins fall into the water-scarce condition : below 1000 cum per annum.
Further reductions below 1000 cum per year per person, can cause chronic shortages of fresh water, adversely impact food production, restrict econonic growth and damage ecosystems.
Since clean fresh water is a limited resource, water governance, management and efficient use is the only alternative.
Reference : Water Resources of Andhra Pradesh : Gupta, Chappuis, Tucker