Personal tools
 
Sections
Goals
Clean and Sufficient Water Preservation of Wild Lands, Habitat & Biodiversity
Indicator Maps
Goals
Climate Protection Responsible Land Use Sustainable Transportation
Indicator Maps
Goals
Food Security Health Equity Income Equity
Indicator Maps
Goals
Healthy Living Choices Quality Educational Opportunities
Indicator Maps
You are here:   Home → Natural Environment → Snow Water Equivalents
Document Actions

Indicator: Snow Water Equivalents

Data and Data Discussion provided by Sustainable Seattle

Snow-Water Equivalents

view full size
Upstream Indicators
  •   Carbon Footprint --- Since 2004, the state's and King County's emissions have been on the rise. In particular, transportation related GHG emissions and total energy use in King County continue to rise.  (view data graph)
more info
Downstream Indicators
  •   Drinking Water Quality --- Seattle Public Utilities (SPU) regularly tests its water for 179 compounds, including metals, chemical contaminants and disease-causing organisms. From 2001 through 2008, SPU-supplied water easily met all state and federal drinking water standards. No compounds were detected above allowable levels.  (view data graph)
  •   Wild Salmon --- Many of Puget Sound's salmon stocks have experienced substantial declines over the past 50-100 years due to overfishing, dams, and habitat degradation. Although the number of mature, adult chinook salmon returning to their stream of origin were almost twice in 2006 as high as 2005 levels, they comprised only 25 percent of the long-term chinook population target.  (view data graph)
more info
Related Goals

Sustainability Snapshot:

It is difficult to think of an element more essential to the health of human communities or their economy than water. Abundant and clean water is indicative of a healthy ecosystem and essential to protect human, plant and animal health. In Central Puget Sound, annual snow fall provides a major source of freshwater. Snow water equivalents provides a measure of long-term trends for annual snow fall.

Sustainability Trend:

Patterns in snow water equivalents for Olallie Meadows, near Snoqualmie Pass, have suggested major declines in snow pack over the last 30 years, with recent years falling well below the long-term annual average.

Data Discussion

The Indicator Defined

Snow Water Equivalent (SWE) is a common snowpack measurement. It is the amount of water contained within the snowpack. It can be thought of as the depth of water that would theoretically result if you melted the entire snowpack instaneously.

Data Interpretation/Evaluation

Patterns in snow water equivalents for Olallie Meadows, near Snoqualmie Pass, have suggested major declines in snow pack over the last 30 years, with recent years falling well below the long-term annual average.  The change in mean April 1 snow pack for the 1976-2008 period versus the 1946-1976 period is substantial. Since the two periods feature nearly identical overall precipitation, the main change is due to temperature. 

Annual Cascade Mountain snow trends are also reflected in the long-term flow patterns for two randomly selected streams in the King County area.  Stream flow has varied widely through the years.  But there has been a general decline of stream flow for Taylor and Issaquah Creeks that represent respectively 17.2 and 56.6 mi2 of drainage area.  2002 flows were as low as any in the record since 1964 and in most years since these creeks have showed less flow than in many other years.  In fact, since 2000 throughout King County streams in general have exhibited fewer days when established minimum flows were met.

Data Source and Limitations

This indicator was prepared by Sustainable Seattle with research and interpretation consultation from Dr. R. Warren Flint of Five E’s Unlimited for Communities Count.  

The amount of snow pack (depth) accumulated in the Cascade Mountains each year is a good indicator of projected water supply.  Because snow pack has not been measured consistently every season, however, the measure of snow-water equivalents can be substituted for snow pack measures because there is a relationship (correlation) between the two of greater than 90% (r=0.9).

The snow pack information and snow-water equivalent measures were obtained from US Department of Agriculture SNOTEL Program . 

Stream flow data were obtained from the U.S. Department of the Interior | U.S. Geological Survey WaterWatch Program. 

collapse all