The average annual water availability of the country is assessed as 1869 billion cubic metres (BCM). Of this, total utilisable water resource is assessed as 1123 BCM, surface water 690 BCM and ground water as 433 BCM. The per capita availability of water at national level has been reduced from about 5177 m3 (cubic metres) in 1951 to the estimated level of 1,820 m3 in 2001 with variation in water availability in different river basins.