Project Watershed Central New York

A watershed or water basin is the region of land that drains into a specified body of water, such as a river, lake, sea, or ocean. Rain that falls anywhere within a given body of water's watershed will eventually drain into that body of water.

The term watershed can also mean the topographical dividing line between water basins: watersheds usually run along mountain ridges. Current usage is watershed divide.

Each area of a drainage basin has its own drainage system.