Lake Sawyer

Lake Sawyer is a freshwater lake in Black Diamond, Washington. With a surface area of 310 acres (1.3 km2), it is the fourth-largest natural lake in King County.[3]

Lake Sawyer
An expanse of open water with a patch of lily pads in the foreground, with houses and a forest of evergreen trees on the opposite shoreline
View from Lake Sawyer Regional Park
Location of Lake Sawyer in Washington, USA.
Location of Lake Sawyer in Washington, USA.
Lake Sawyer
Location of Lake Sawyer in Washington, USA.
Location of Lake Sawyer in Washington, USA.
Lake Sawyer
LocationBlack Diamond, Washington, United States
Coordinates47°20′0″N 122°2′15″W
Part ofGreen River watershed
Primary inflowsBeaver Creek, Rock Creek
Primary outflowsCovington Creek
Catchment area8,320 acres (33.7 km2)
Basin countriesUnited States
Surface area310 acres (1.3 km2)
Average depth25 feet (7.6 m)
Max. depth58 feet (18 m)
Residence time19 weeks[1]
Surface elevation495 feet (151 m)
References[2]

Lake Sawyer is underlain by glacial outwash and till dating from the Vashon Glaciation, as well as older glaciations that occurred during the Pleistocene.[4] The bedrock underlying this mass of sediments is classified as the Hammer Bluff Formation, which was deposited in the Miocene epoch and consists of sandstone with some volcanic deposits.[5][6] Groundwater outflow from the lake is believed to occur primarily in the northeast and southwest corners.[7] Lake Sawyer is classified as mesotrophic, with algal growth limited by phosphorus availability.[8] A 1994 survey found 23 species of plants growing in the lake and along its shorelines, including the invasive Myriophyllum spicatum and Nymphaea odorata.[9]

A concrete dam was built at the outlet in 1952 to regulate the lake level.[10] Beginning in 1983, the city of Black Diamond discharged outflow from a wastewater treatment plant near the outlet of Rock Creek, one of the lake's main inflows, into the lake.[11] After a 1989 study determined that the plant was causing eutrophication of the lake,[12] the outflow was diverted into a sewer line in 1992.[11]

Lake Sawyer is stocked with rainbow trout, coastal cutthroat trout, and kokanee salmon for recreational fishing. Several resident species such as largemouth bass can also be caught in the lake.[13]

References
  1. Pelletier & Joy, p. 9.
  2. McConnell, J. B.; Bortleson, G. C.; Innes, J. K. (1976). Data on Selected Lakes in Washington, Part 4 (PDF). Washington Water Supply Bulletin (Report). Vol. 42. Washington Department of Ecology. pp. 118–121.
  3. "Lake Sawyer". King County, Washington. September 9, 2019. Retrieved January 16, 2023.
  4. Lake Sawyer Hydrogeologic Study, p. 22–23.
  5. Lake Sawyer Hydrogeologic Study, p. 23.
  6. Mullineaux, Donald R. (1970). Geology of the Renton, Auburn, and Black Diamond Quadrangles, King County, Washington (PDF) (Report). United States Geological Survey. pp. 24–26.
  7. Lake Sawyer Hydrogeologic Survey, p. 25–34.
  8. Lake Sawyer Management Plan, Executive Summary, pp. 2–4.
  9. Lake Sawyer Management Plan, Chapter 4, pp. 19–21.
  10. Palletier & Joy, p. 1.
  11. Lake Sawyer Management Plan, Executive Summary, p. 1.
  12. Pelletier & Joy, p. IV.
  13. "Lake Sawyer". Washington Department of Natural Resources. Retrieved January 16, 2023.

Bibliography
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