Land area where water converges to a common outlet
The Basin
A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean.
A basin is separated from adjacent basins by a perimeter, the drainage divide, made up of a succession of elevated features, such as ridges and hills. A basin may consist of smaller basins that merge at river confluences, forming a hierarchical pattern.
Text adapted from Wikipedia, CC BY-SA 4.0. Photograph: Wolfgang Moroder (see Commons), Wikimedia Commons.