Topic summary
Drainage basins
Extracted from the Wikipedia article Drainage basin.
Drainage basins are similar but not identical to hydrologic units, which are drainage areas delineated so as to nest into a multi-level hierarchical drainage system. Hydrologic units are defined to allow multiple inlets, outlets, or sinks. In a strict sense, all drainage basins are hydrologic units, but not all hydrologic units are drainage basins.