A
drainage basin is an extent of
land where
water from
rain or
snow melt drains downhill into a body of water, such as a
river,
lake,
reservoir,
estuary,
wetland,
sea or
ocean. The drainage basin includes both the streams and rivers that convey the water as well as the land surfaces from which water drains into those channels, separated from adjacent basins by a
drainage divide,water Shed or Water table .
[1]The drainage basin acts like a funnel - collecting all the water within the area covered by the basin and channeling it into a waterway. Each drainage basin is separated topographically from adjacent basins by a ridge, hill or mountain, which is known as a water divide. Other terms that can be used to describe the same concept are catchment, catchment area, catchment basin, drainage area, river basin and water basin.[2]
In the technical sense, a watershed refers to a divide that separates one drainage area from another drainage area.[3] However, in the United States and Canada, the term is often used to mean a drainage basin or catchment area itself. Watersheds drain into other watersheds in a hierarchical form, larger ones breaking into smaller ones or sub-watersheds with the topography determining where the water flows. Understanding geomorphology is essential in understanding how watersheds interconnect.[4]
Drainage basins of the principal oceans and seas of the world. Grey areas are endorheic basins that do not drain to the ocean.
