Abstract:
Hydrology is a branch of Earth Science. The importance of hydrology in the assessment,
development, utilisation and management of the water resources, of any region is being increasingly realised at all levels. It was in view of this that the United Nations proclaimed the
period of 1965-1974 as the International Hydrological Decade during which, intensive efforts
in hydrologic education research, development of analytical techniques and collection of hydrological information on a global basis, were promoted in Universities, Research Institutions,
and Government Organisations.
1.1 WORLD’S WATER RESOURCES
The World’s total water resources are estimated at 1.36 × 108 Μ ha-m. Of these global water
resources, about 97.2% is salt water mainly in oceans, and only 2.8% is available as fresh
water at any time on the planet earth. Out of this 2.8% of fresh water, about 2.2% is available
as surface water and 0.6% as ground water. Even out of this 2.2% of surface water, 2.15% is
fresh water in glaciers and icecaps and only of the order of 0.01% is available in lakes and
streams, the remaining 0.04% being in other forms. Out of 0.6% of stored ground water, only
about 0.25% can be economically extracted with the present drilling technology (the remaining being at greater depths). It can be said that the ground water potential of the Ganga Basin
is roughly about forty times the flow of water in the river Ganga.
