Water Quantity and Quality 

Abundant and clean water is indicative of a healthy ecosystem and essential to protect human, plant and animal health. Freshwater ecosystems provide many valuable commodities and services to society, beyond simply direct water supply. Environmental contaminants from urban development and industrial or agricultural production can affect water quality. Once degraded, aquatic systems are often impossible to replace. The demand for water resources in the Puget Sound region is being driven by an increasing population as well as by greater energy demand from hydroelectric generation. At the same time, capacity is declining through over-harvesting, inappropriate agricultural practices, climate change and pollution.

• Annual snow fall is a major source of freshwater in King County. The amount of water contained in snow pack is measured by snow-water equivalents (SWE). (figure 1)

• Patterns in SWE for Olallie Meadows, near Snoqualmie Pass, suggest 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.

• Long-term flow patterns for streams in the region reflect snow trends in the Cascades. Stream flow has varied widely through the years, but since 2000, streams throughout King County have generally exhibited fewer days when established minimum flows were met (data not shown).

• Salmon populations are important to the economy, culture and ecology of King County and the Pacific Northwest. The condition of salmon habitat is related to water quality. Fewer salmon have returned to spawning creeks over the years.(figure 2) This is especially apparent with regards to Chinook salmon.

• Chinook salmon in the Cedar River have shown a large variation in return counts. Much of this variation can be due to natural conditions such as ocean warming cycles and precipitation. Human activities, including land-use practices, alter natural stream flow, quality of that flow and natural habitat. From 1988 to 2004, the counts have remained very low for adult spawners.

• In general, Chinook populations, while increasing over the past 10 years, are still drastically short of historical levels and 2055 targets.

• People living in the King County region would seem to be sensitive to the importance of freshwater supply. The rate of water consumption has generally declined over the last 18 years, despite population growth.

• Because of its size and location, Lake Washington can provide a good picture of overall water quality in the region. Water quality is measured by clarity, algal levels and phosphorus. (figure 3) Over the last 3 years, all 3 measures have indicated a healthy condition for this large freshwater ecosystem (data not shown).

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