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(geography) An extent of land where water from rain or snow melt drains downhill into a river or series of rivers.

The Amazon river basin

(geography) An extent of land where water from rain or snow melt drains downhill into a river or series of rivers.

The Mississippi River drains the largest area of any U.S. river, much of it agricultural regions. Agricultural runoff and other water pollution that flows to the outlet is the cause of the hypoxic or dead zone in the Gulf of Mexico.

(geography) An extent of land where water from rain or snow melt drains downhill into a river or series of rivers.

Major continental divides, showing how terrestrial drainage basins drain into the oceans. Grey areas are endorheic basins that do not drain to the oceans