| the area drained by a river and all its tributaries. Also called catchment area, drainage area. Compare watershed (def. 2). |
| drainage basin n. An area drained by a river system. |
drainage basin  (drā'nĭj) Pronunciation Key
An area drained by a river system. A drainage basin includes all areas that gather precipitation water and direct it to a particular stream, stream system, lake, or other body of standing water. |
drainage basin
area from which all precipitation flows to a single stream or set of streams. For example, the total area drained by the Mississippi River constitutes its drainage basin, whereas that part of the Mississippi River drained by the Ohio River is the Ohio's drainage basin. The boundary between drainage basins is a drainage divide: all the precipitation on opposite sides of a drainage divide will flow into different drainage basins.
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