Subbasins

Part of speech: noun

Definitions

1. A smaller basin that drains into a larger watershed or river system
2. An area of land that collects and channels water to a main drainage system
3. A subregion within a larger hydrological basin contributing to the flow of water and sediment

Etymology: "Subbasins" is the plural of "subbasin," a compound formed from the prefix "sub-" (from Latin "sub," meaning "under" or "below," and here used in the sense of "subordinate to" or "smaller than") and "basin." The base word "basin" comes from Old French "bacin," a vessel for holding liquid, and originally named a shallow container. Its geographical sense, a tract of land drained by a river system, grew from the image of land sloping down to collect water the way a bowl collects it. Attaching "sub-" to "basin" gives a term for a smaller drainage area nested inside a larger one. Hydrologists use it so that a river system can be divided into a hierarchy of basins and their tributary catchments, each contributing water and sediment to the one downstream. The plural form simply counts these nested units, which is why the term is most often used when describing a large watershed broken into several parts.