WILLAMETTE BASIN WATERSHEDS

Watershed Map

A watershed is the divide separating one drainage area from another (Chow, 1964). The term "watershed" is commonly used to refer to an area; specifically, the area in which all surface waters flow to a common point.

The U.S. Geological Survey (USGS) has developed a hierarchy for defining watersheds of varying sizes. The smallest subdivision in the USGS hierarchy is the Subbasin. Almost all of the subbasins are larger than 700 square miles in size. Subbasins are equivalent to "fourth field watersheds.

Twelve 4th field watersheds are located within the Willamette Basin.

Lower Willamette Clackamas Tualatin Middle Willamette Yamhill Molalla/Pudding North Santiam South Santiam Upper Willamette McKenzie Middle Fork Willamette Coast Fork Willamette