Lower Cowlitz

Watershed Hydrology

The Lower Cowlitz Watershed (HUC 17080005) covers an area of approximately 3,157 square miles in southwest Washington. The watershed is characterized by a network of streams and tributaries that drain into the Cowlitz River. The hydrology of the watershed is heavily influenced by precipitation, which is distributed evenly throughout the year. The region receives an average of 120 inches of rainfall annually. The area is also known for its significant snowpack, which can accumulate up to 200 inches in the higher elevations. The surface water in the watershed is used for irrigation, municipal and industrial purposes, and power generation. The reservoirs in the watershed contain regulated flows of water that are used for flood control, power generation, and water supply. Climate trends indicate increased precipitation and temperatures in the region over the past several decades.


Surface Flows

Lower Cowlitz Watershed

Snowpack Depths

Lower Cowlitz Watershed

Dams & Reservoirs

Lower Cowlitz Watershed

Groundwater Levels

Lower Cowlitz Watershed

Lower Cowlitz Rivers

Rivers of the Watershed