Home Text size go
Willamette Basin Explorer Home
Willamette Basin Watersheds
Willamette Basin Watersheds
Watersheds ImagemapLower WillametteClackamasTualatinMiddle WillametteYamhillMolalla/PuddingNorth SantiamSouth SantiamUpper WillametteMcKenzieMiddle Fork WillametteCoast Fork Willamette

Watersheds in the Willamette Basin

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, Middle Willamette, Upper Willamette, Coast Fork Willamette, Middle Fork Willamette, McKenzie, South Santiam, North Santiam, Clackamas, Molalla/Pudding, Yamhill, and Tualatin.

Watershed thinking challenges our conceptions of place. The word “watershed” can relate to the physical boundary of a hydrologic drainage, or it infers the complexity and interrelationships that exist in the ecological and social systems within that area, or it is a metaphor in our language for a dramatic moment. 

Watershed thinking allows us to move beyond political boundaries. American explorer, John Wesley Powell, argued that the counties of the West should be organized by small watershed boundaries, because the success of agricultural settlements lay in wise management of local water resources.

Sources:

Chow, Ven Te, 1964. Handbook of applied hydrology. McGraw-Hill.