LAKE SAMMAMISH IN TRANSITION
A relatively shallow, low-land lake in central King County, Sammamish has a surface area of approximately 8 square miles. Entirely surrounded by land zoned for high-density urban growth, it is in great jeopardy for survival as a healthy recreational resource and as salmonid habitat. We are in a position still to make decisions that will affect positively its survival, but only if we act quickly and decisively. Decisions, however, must be based on knowledge and the following discussion is meant to provide the basis for the decisions that soon must be made. Deferring these decisions is not an option, because that in itself is a decision to do nothing and the health of the lake inevitably will continue to worsen.
The 98 square mile Lake Sammamish watershed stretches from Redmond through Bellevue, and Issaquah to Preston and Hobart, and empties into the lake through numerous small streams and rivulets. The largest of these, Issaquah Creek, provides about 70% of the inflow to the lake. This water system is in continuity with groundwater in the Issaquah aquifer. Historically, the large volume of rain in this watershed (nearly twice the 35 inches a year that falls on Seattle), has been absorbed by the surrounding forests. Like a well-regulated reservoir, loose, sponge-like forest soils retain and then slowly release stored rainwater into the aquifer and surface streams. Such a natural system prevents flooding in winter but continues to supply clean, cold water to streams and aquifer in the dry months. Where forests have been replaced by impervious surfaces--roofs, roads, parking lots--the loss of rain storage capacity as well as a more rapid rate of runoff, can lead to flooding. The increased frequency of "100-year floods" in recent years despite the absence of "100-year storms" is an identifiable consequence of land conversion from forest to subdivision.
Flood destruction of property is only one of many problems. Erosion is another. Once vegetation has been removed, rain easily washes the exposed soils and sediments downhill into creeks and lake. Soils in this watershed are high in phosphorus, a fertilizer. Deltas of mud and rock form in the lake at outfalls of creeks and drainage culverts, smothering gravels with sediment, filling coves, and turning lakewater murky. This process can be dramatic: a single storm (1/9/90) transported over 40,000 tons of soil, rock and sediment into the lake at the mouth of Lewis Creek, following clearing of only 2% of the North Village project on Cougar Mountain. This despite developer projections that the entire project would result in the transport of less than 10,000 tons total of material into the lake!
In addition to direct property damage and delta formation, floods and erosion also damage the fisheries. Salmonids, particularly, depend on a specific fresh water environment--cold, well-oxygenated water and loose, clean gravels--to spawn successfully and for their eggs to incubate. Seven species of salmonid are found in Lake Sammamish, but at least one--a sub-species of kokanee peculiar to Lake Sammamish--is on the verge of extinction. Shore-line spawning sockeye and steelhead are rapidly disappearing from this system also.
Toxic wastes in non-point runoff also harm water quality. Flooding increases the delivery of toxins from lawns, gardens and roads into the lake. Petroleum products and herbicides are serious concerns but phosphorus remains the number one threat for Lake Sammamish. This naturally occurring substance is necessary for life in very small quantities. However, rapid urbanization has led to increased phosphorus loading to the lake from non-point sources-- soil erosion, garden fertilizers, detergents, pet wastes and failing septic systems. Phosphorus is a fertilizer so it stimulates growth of aquatic plants, including dense algae populations that turn the lake a cloudy green and form surface scums. As the algae die and decay, the lake looks and smells bad, repelling swimmers and boaters. The decaying algae also rob the water of the dissolved oxygen needed by fish, sometimes precipitating dramatic fish-kills.
Studies of Lake Sammamish by government agencies and the University of Washington conclude that without reduction of phosphorus loading to the lake, its water quality will deteriorate to levels last seen when the city of Issaquah used to dump its sewage directly into the lake. Metro was formed in the early 1970's, at huge public cost, to restore good water quality in Lakes Washington and Sammamish. Sanitary sewers and treatment plants were built to achieve the community's clean water goal. But there is no easy "fix" for non-point pollution--prevention is the best and most cost effective technology available!
A lake reflects its watershed. Conversion of the watershed from forests to cities causes deterioration of water quality. That means the problem is us--everyone who lives in the watershed or even drives through it! Clearly we all have to be part of the solution. As the area urbanizes, the community must decide what to do with Lake Sammamish. Shall we continue to pollute until it is no longer an inviting recreational resource--a place to swim, sail, ski? Shall we continue to pollute until it is uninhabitable by salmon and eagles? Shall we continue to pollute until Sammamish goes "Green Lake?" Or can we rise to the challenge of protecting Sammamish as an invaluable amenity in our community life? Now is crunch time.