| Noun | 1. | catchment area - the entire geographical area drained by a river and its tributaries; an area characterized by all runoff being conveyed to the same outlet; "flood control in the Missouri basin"detention basin - a storage site (such as a small reservoir) that delays the flow of water downstream retention basin - a storage site similar to a detention basin but the water in storage is permanently obstructed from flowing downstream geographic area, geographic region, geographical area, geographical region - a demarcated area of the Earth |