Everyone lives in a watershed. A watershed is an area of land that drains all the streams and rainfall to a common outlet such as the outflow of a reservoir, mouth of a bay, or any point along a stream channel. The word watershed is sometimes used interchangeably with drainage basin or catchment. Ridges and hills that separate two watersheds are called the drainage divide. The watershed consists of surface water--lakes, streams, reservoirs, and wetlands--and all the underlying groundwater. Larger watersheds contain many smaller watersheds or subwatersheds. Smaller watersheds become part of larger watersheds, as streams feed into rivers and rivers flow into lakes and oceans. Human impacts on our watersheds can negatively affect the health of our streams, rivers, and lakes.