Identify Modern, and Project Future, Glacial Contribution to Summer Stream Flow in the Skagit River Watershed
National Park Service Climate Change Grant: $74,000 (2010–2011)
Additional Funds Needed for Completion: $100,000
Background and motivation: The Skagit River Valley is the most heavily glaciated watershed in the lower 48 states with more than 390 glaciers. The river is the largest tributary of Puget Sound, and the only one that hosts all five native species of Pacific salmon. A major reason the Skagit provides critical habitat for salmonids is that its glaciers provide approximately 120–180 billion gallons of cold, fresh water every summer to buffer lakes and streams from drought. Glacial meltwater also fuels the region’s hydroelectric industry, and provides fresh water for domestic and agricultural uses.
Since about 1900, the area of glaciers in the North Cascades has declined by about 50%, following the global pattern of rapid loss of ice from mountain regions. In the Skagit Basin, the volume of ice lost since 1993 equals about 400 billion gallons of water, or about one month’s continuous flow of the Skagit River. Continued loss of this cold, summer source of fresh water from glaciers is in addition to the significant decline over the last 50 years of water from snow as well. Loss of summer base flows impacts current and future management of water resources. This project seeks to develop an accurate model for modern and future glacial meltwater contributions to summer stream flow in the Skagit watershed to inform restoration and management efforts.
(top photo) Silver Glacier 1958 (Post) and (bottom) 2006 (Scurlock). In 1913 the glacier covered all of Silver Lake.
Objective: The initial objective is to update a 40-year-old inventory of glacier area and altitude distribution in the Sauk River watershed; work is already underway to update other Skagit tributaries. The second objective is to improve two models of stream flow to assess future changes in glacial meltwater production. The first model is based on mass balance measurements taken on five glaciers since 1993, and will be expanded to the entire Skagit. Output from this empirical model will be used to calibrate and expand a DHVSM model to include glaciers.
Project Team: The project team consists of Dr. Jon L. Riedel of the U.S. National Park Service and Dr. Alan Hamlet of the University of Washington.
Expected Outcome: Glacial meltwater estimates from these models will be linked to a larger hydrodynamic model of the Skagit River and provide a basis for assessment of changes to water temperature. Model results will inform a wide audience on the industrial, social, agricultural, and ecological consequences of loss of fresh water resources due to climate change.