The approximately 394 glaciers in the Skagit basin provide 8 to 12 percent (120-180 billion gallons) of the Skagit River’s summer flows. This important coldwater source is provided when rivers and streams are at their lowest and warmest. This is important for both people and the ecosystem. Information about some of the monitoring of glacial contributions to Skagit creeks, lakes and rivers can be found here.
Since 1900 the glaciers in the Skagit basin have retreated, and the loss of glacial area has accelerated in response to post-1970 warming with a 50 percent loss between 1900 and 1998 (Granshaw, 2002). Some of the observed losses of glacial mass in the North Cascades are telltale signs of higher temperatures.
Silver Glacier feeding the head of Ross Lake has diminished greatly in the past century. About 1900 A.D. the glacier covered Silver Lake. From 1958 to 2006 the glacier pulled back from the lake, and a small ice mass remains in the head of the valley (Photo 1).
Similarly, the Easton Glacier (Photo 2) on the southern slopes of Mount Baker has retreated significantly in recent years. The Easton Glacier is one of seven glaciers that drains into Baker Lake that has been monitored since 1983.
There have been a few periods of glacial volume accumulation over the last 100 years, including as recently as 2011. However, the Skagit basin is rapidly losing its cold water “bank account.” In fact since 1993, the Skagit Basin has lost 400 billion gallons, the equivalent of 44 years of Skagit County water supply at the 2010 rate of use, with the retreat and loss of the glaciers. Continued glacial retreat is expected and will exacerbate summertime low flows and intensify rising water temperatures in the Skagit basin.
More information is available in the recent Northwest Science Special Issue article “Impact of Recent Glacial Recession on Summer Streamflow in the Skagit River.”
Find recent report here.