| the area drained by a river and all its tributaries. Also called catchment area, drainage area. Compare watershed (def. 2). |
| catchment area n.
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catchment area
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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