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Lake Washington

Lake Washington

One of the great messages to come out of the environmental movement of the 1960s and 1970s is that, while humans can cause pollution , they can also clean it up. Few success stories illustrate this point as clearly as that of Lake Washington. Lake Washington lies along the state of Washington's west coastline, near the city of Seattle. It is 24 miles (39 km) from north to south and its width varies from 24 miles (36 km).

For the first half of this century, Lake Washington was clear and pristine, a beautiful example of the Northwest's spectacular natural scenery. Its shores were occupied by extensive wooded areas and a few small towns with populations of no more than 10,000. The lake's purity was not threatened by Seattle, which dumped most of its wastes into Elliot Bay, an arm of Puget Sound. This situation changed rapidly during and after World War II. In 1940, the spectacular Lake Washington Bridge was built across the lake, joining its two facing shores with each other and with Seattle. Population along the lake began to boom, reaching more than 50,000 by 1950.

The consequence of these changes for the lake are easy to imagine. Many of the growing communities dumped their raw sewage directly into the lake or, at best, passed their wastes though only preliminary treatment stages. By one estimate, 20 million gallons (76 million liters) of wastes were being dumped into the lake each day. On average these wastes still contained about half of their pollutants when they reached the lake. In less than a decade, the effect of these practices on lake water quality were easy to observe. Water clarity was reduced from at least 15 ft (4.6 m) to 2.5 ft (0.8 m) and levels of dissolved oxygen were so low that some species of fish disappeared. In 1956, W. T. Edmonson, a zoologist and pollution authority, and two colleagues reported their studies of the lake. They found that eutrophication of the lake was taking place very rapidly as a result of the dumping of domestic wastes into its water.

Solving this problem was especially difficult because water pollution is a regional issue over which each individual community had relatively little control. The solution appeared to be the creation of a new governmental body that would encompass all of the Lake Washington communities, including Seattle. In 1958, a ballot measure establishing such an agency, known as Metro, was passed in Seattle but defeated in its suburbs. Six months later, the Metro concept was redefined to include the issue of sewage disposal only. This time it passed in all communities.

Metro's approach to the Lake Washington problem was to construct a network of sewer lines and sewage treatment plants that directed all sewage away from the lake and delivered it instead to Puget Sound. The lake's pollution problems were solved within a few years. By 1975 the lake was back to normal, water clarity returned to 15 ft and levels of potassium and nitrogen in the lake decreased by more than 60 percent. Lake Washington's biological oxygen demand (BOD), a critical measure of water purity, decreased by 90 percent and fish species that had disappeared were once again found in the lake.

See also Aquatic chemistry; Cultural eutrophication; Waste management; Water quality standards

[David E. Newton ]



Edmonson, W. T. "Lake Washington." In Environmental Quality and Water Development, edited by C. R. Goodman, et al. San Francisco: W. H. Freeman, 1973.

. The Uses of Ecology: Lake Washington and Beyond. Seattle: University of Washington Press, 1991.


Li, Kevin. "The Lake Washington Story." King County Web Site. May 2, 2001 [June 19,2002]. <>.

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