Upper Cowlitz

Watershed Hydrology

The Upper Cowlitz Watershed (HUC 17080004) covers approximately 1,219 square miles in western Washington state. The region's hydrology is influenced heavily by the nearby Mount Rainier, which provides significant surface water and snowpack. The snowpack in the region is an important source of water for the watershed's streams and rivers, with approximately 60% of the annual water supply coming from snowmelt. The region also contains several reservoirs, including Riffe Lake and Mayfield Lake, which supply water for irrigation, hydropower, and drinking water. Interesting climatic trends in the Upper Cowlitz Watershed include increasing temperatures and decreasing snowpack levels, which may have significant impacts on the region's hydrology and ecology in the future. Despite these changes, the watershed remains an important natural resource for the region, providing clean water, recreation opportunities, and wildlife habitat.


Surface Flows

Upper Cowlitz Watershed

Snowpack Depths

Upper Cowlitz Watershed

Dams & Reservoirs

Upper Cowlitz Watershed

Groundwater Levels

Upper Cowlitz Watershed

Upper Cowlitz Rivers

Rivers of the Watershed