WATER AND AIR

The stereotype of western Oregon is that it's rainy and wet--and thus water is plentiful. However, 70-80% of the annual precipitation in the Willamette Basin falls between October and March; less than 5% in July and August. Low levels of rainfall during summer result in low stream flows and constrained water supplies at the time of the year when demands are often highest. Thus, even in a region of the state known for its abundant rainfall, water is scarce at certain time of year and at certain locations.

Precipitation is the ultimate water source. The amount of precipitation increases sharply with elevation, ranging from 40-50 inches (100-130 cm) per year in the valley to almost 200 inches (500 cm) near the crests of the Coast and Cascade ranges.

Excerpted with permission from J. Baker, J. Van Sickle, and D. White. (2002). Water Sources and Allocation. In D. Hulse, S. Gregory, and J. Baker (Eds.). Willamette River Basin planning atlas, 2nd. Edition, (pp. 34-35). Corvallis: Oregon State University Press