1. The two main sources of water in India are rainfall and the snowmelt of glaciers in the Himalayas. Although reliable data on snow cover in India are not available, it is estimated that some 5000 glaciers cover about 43000 km$^2$ in the Himalayas with a total volume of locked water estimated at 3870 km$^3$. considering that about 10000 km$^2$ of the Himalayan glacier is located within India, the total water yield from snowmelt contributing to the river runoff in India may be of the order of 200 km$^3$/year. Although snow and glaciers are poor producers of fresh water, they are good distributors as they yield at the time of need, in the hot season.

2. The total surface flow, including regenerating flow from ground water and the flow from neighbouring countries is estimated at 1869 km$^3$ /year, of which only 690 km$^3$ are considered as utilizable in view of the constraints of the present technology for water storage and inter – state issues. An important part of the surface water resources leaves the country before it reaches the sea.

The water resources of India may be summarized as follows: