As per a report of the National Commission on Integrated Water
Resources Development (NCIWRD), the total water availability of
India received through precipitation is about 4000 billion cubic
meter per annum. After evaporation, 1869 billion cubic metres water
is available as natural run off. Due to topographical and other
factors, the utilizable water availability is limited to 1122
billion cubic metres, comprising of 690 billion cubic metres of
surface water and 432 billion cubic metres of rechargeable ground
water. As per NCIWRD (1999), the total water demand of the country
has been estimated as 710 billion cubic metres, 843 billion cubic
metres and 1180 billion cubic metres for the years 2010, 2025 and
2050 respectively. Availability of water is highly uneven in both
space and time, with monsoon confined only to four months in a
year. Precipitation varies from 100 millimeter (mm) in the Western
parts of Rajasthan to over 10,000 mm in Meghalaya.
