Basin wise water resource project development
Ø The total land area that contributes water to a river is called a Watershed, also called differently as the Catchment, River basin, Drainage Basin, or simply a Basin.
Ø A watershed may also be defined as a geographic area that drains to a common point, which makes it an attractive planning unit for technical efforts to conserve soil and maximize the utilization of surface and subsurface water for crop production.
Ø Thus, it is generally considered that water resources development and management schemes should be planned for a hydrological unit such as a Drainage Basin as a whole or for a Sub-Basin, multi-sectorially, taking into account surface and ground water for sustainable use incorporating quantity and quality aspects as well as environmental considerations.
Ø Let us look into the concept of watershed or basin-wise project development in some detail
Ø The objective is to meet the demands of water within the Basin with the available water therein, which could be surface water, in the form of rivers, lakes, etc. or as groundwater
Ø The source for all these water bodies is the rain occurring over the Watershed or perhaps the snowmelt of the glacier within it, and that varies both temporally and spatially.
Ø Further due to the land surface variations the rain falling over land surface tries to follow the steepest gradient as overland flow and meets the rivers or drains into lakes and. ponds
Ø The time for the overland flows to reach the rivers may be fast or slow depending on the obstructions and detentions it meet on the way.
Ø Part of the water from either overland flow or from the rivers and lakes penetrates into the ground and recharge the ground water.
Ø Ground water is thus available almost throughout the watershed, in the underground aquifers. The variation of the water table is also fairly even, with some rise during rainfall and a gradual fall at other times.
water in the rivers is mostly available during the rains. When the rain stops,
part of the ground water comes out to recharge the rivers and that results in
the dry season flows in rivers.