Water Temperature Monitoring and Modeling of the Upper Skagit River Basin

Water Temperature Monitoring and Modeling of the Upper Skagit River Basin

Seattle City Light Endangered Species Act Funding: $50,000 (2009-2012)
Additional Funds Needed for Completion: $100,000

Ross Lake, Upper Skagit Basin

Ross Lake, Upper Skagit Basin

Background and motivation: The Upper Skagit River Basin is 2,000 square kilometers in area, and extends from its headwaters in British Columbia to the Skagit gorge above the town of Newhalem, Washington. The basin includes the Upper Skagit River, major tributaries including Lightning, Ruby, and Big Beaver creeks, and three reservoirs: Ross, Diablo, and Gorge lakes. The large amounts of cold water flowing from the Upper Skagit are critical to sustaining the largest bull trout population in Washington State, and the largest wild Chinook salmon run in the Puget Sound. The mainstem Skagit also supports the largest pink and chum salmon runs in the lower 48 states. The Skagit is the most snow-dominated major river system in the Puget Sound. Increases in air temperature and shifts in rainfall and snowfall patterns predicted under climate change models are expected to result in the substantial warming of surface waters in the Upper Skagit River Basin, and the 155 km of mainstem river located downstream. Warming will likely have a profound impact on the Skagit’s riverine and reservoir ecosystems and on the Endangered Species Act-listed bull trout, steelhead, and Chinook salmon dependent upon them. This project was initiated in 2001 by the deployment of water temperature measurement devices in the major tributaries of the Upper Skagit Basin by Seattle City Light (SCL). The University of Washington’s Climate Impacts Group (CIG) used this data to predict the warming and variability of the Upper Skagit’s stream temperatures in the year 2040 using a regression modeling approach. SCL and the National Park Service expanded the Upper Skagit temperature monitoring program to include continuous temperature profiling at five stations in Ross Lake.

Skagit River Bull Trout

Skagit River Bull Trout

Objectives: Upper Skagit Basin project objectives: 1) monitor and describe natural spatial and temporal variability in stream, river, and reservoir temperatures, 2) predict water temperatures under future climate warming scenarios and hydrodynamic stream and reservoir temperature models, and 3) evaluate impacts of water temperature changes on bull trout.

Project Team: The project team consists of Dr. Ed Connor (Seattle City Light) and Ashleigh Rawhauser and Reed Glesne (National Park Service, North Cascades National Park complex).

Expected Outcome: We are proposing to complete a 2-D hydrodynamic water quality model (CE-QUAL-W2) to predict changes in stream, river, and reservoir temperature regimes under future climate scenarios. This model will be used with physiological tolerance, behavior, life- cycle, and population models to predict the impacts of climate change on bull trout in the Upper Skagit River Basin. The hydrodynamic model will also be used to predict changes in the Skagit River’s temperature regimes downstream of the reservoirs.