Lake Washington
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Lake Washington () is a large freshwater
lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...
adjacent to the city of
Seattle Seattle ( ) is the most populous city in the U.S. state of Washington and in the Pacific Northwest region of North America. With a population of 780,995 in 2024, it is the 18th-most populous city in the United States. The city is the cou ...
, Washington, United States. It is the largest lake in King County and the second largest natural lake in the state of Washington, after Lake Chelan. It borders the cities of Seattle on the west, Bellevue and Kirkland on the east, Renton on the south, and Kenmore on the north, and encloses Mercer Island. The lake is fed by the Sammamish River at its north end and the Cedar River at its south. Lake Washington has been known to the Duwamish and other
Indigenous peoples There is no generally accepted definition of Indigenous peoples, although in the 21st century the focus has been on self-identification, cultural difference from other groups in a state, a special relationship with their traditional territ ...
living on the lake for millennia as (lit. "lake" in Lushootseed). At the time of European settlement, it was recorded as At-sar-kal in a map sketched by engineer Abiel W. Tinkham; and the
Chinook Jargon Chinook Jargon (' or ', also known simply as ''Chinook'' or ''Jargon'') is a language originating as a pidgin language, pidgin trade language in the Pacific Northwest. It spread during the 19th century from the lower Columbia River, first to othe ...
name, ("great/large water"), was also used. Other English names historically used for the lake include Lake Geneva by Isaac N. Ebey; and Lake Duwamish in railroad surveys under Governor
Isaac Stevens Isaac Ingalls Stevens (March 25, 1818 – September 1, 1862) was an American military officer and politician who served as governor of the Territory of Washington from 1853 to 1857, and later as its delegate to the United States House of Represe ...
. Lake Washington received its present name in 1854 after
Thomas Mercer Judge Thomas Mercer (March 11, 1813 – May 25, 1898) was a pioneer associated with the early history of Seattle. Seattle's Mercer Street and Mercer Island, Washington, Mercer Island in Lake Washington bear his name. Biography Early life Merc ...
suggested it be named after
George Washington George Washington (, 1799) was a Founding Fathers of the United States, Founding Father and the first president of the United States, serving from 1789 to 1797. As commander of the Continental Army, Washington led Patriot (American Revoluti ...
, as the new
Washington Territory The Washington Territory was an organized incorporated territory of the United States that existed from March 2, 1853, until November 11, 1889, when the territory was admitted to the Union as the State of Washington. It was created from the ...
had been named the year before. The lake provides boating and sport fishing opportunities. Some fish species found in its waters include sockeye salmon,
coho salmon The coho salmon (''Oncorhynchus kisutch;'' Karuk: achvuun) is a species of anadromous fish in the salmon family (biology), family and one of the five Pacific salmon species. Coho salmon are also known as silver salmon (or "silvers") and is often ...
,
Chinook salmon The Chinook salmon (''Oncorhynchus tshawytscha'') is the largest and most valuable species of Oncorhynchus, Pacific salmon. Its common name is derived from the Chinookan peoples. Other vernacular names for the species include king salmon, quinn ...
,
rainbow trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributary, tributaries of the Pacific Ocean in North America and Asia. The steelhead (sometimes called steelhead trout) is an Fish migration#Classification, ...
,
largemouth bass The largemouth bass (''Micropterus nigricans'') is a carnivorous, freshwater fish, freshwater, ray-finned fish in the Centrarchidae (sunfish) family, native to the eastern United States, eastern and central United States, southeastern Canada an ...
,
smallmouth bass The smallmouth bass (''Micropterus dolomieu'') is a species of freshwater fish in the Centrarchidae, sunfish family (biology), family (Centrarchidae) of the order (biology), order Centrarchiformes. It is the type species of its genus ''Micropterus ...
,
yellow perch The yellow perch (''Perca flavescens''), commonly referred to as perch, striped perch, American perch or preacher is a freshwater perciform fish native to much of North America. The yellow perch was described in 1814 by Samuel Latham Mitchill fr ...
, and
black crappie The black crappie (''Pomoxis nigromaculatus'') is a freshwater fish in the sunfish family ( Centrarchidae). It is endemic to North America, one of the two types of crappies. It is very similar to the white crappie (''P. annularis'') in size, s ...
. Lake Washington has two passenger seaplane bases: Kenmore Air Harbor on its north end; and Will Rogers – Wiley Post Memorial Seaplane Base on its south end, adjacent to Renton Municipal Airport.


Geography

Lake Washington's basin was formed by glacial processes associated with the Puget lobe of the Cordilleran Ice Sheet during the Vashon Glaciation, likely through a combination of preferential erosion of weak rock and sediments by the glacier itself and by subglacial meltwater during the glacier's retreat. At the end of the
Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
, the basin that is now Lake Washington connected directly to the channels of
Puget Sound Puget Sound ( ; ) is a complex estuary, estuarine system of interconnected Marine habitat, marine waterways and basins located on the northwest coast of the U.S. state of Washington (state), Washington. As a part of the Salish Sea, the sound ...
through the north end of the Duwamish Valley. The basin may or may not have been a waterway at this point, as
eustatic sea level The eustatic sea level (from Greek εὖ ''eû'', "good" and στάσις ''stásis'', "standing") is the distance from the center of the Earth to the sea surface. An increase of the eustatic sea level can be generated by decreasing glaciation, inc ...
s were approximately lower than at present and the land around Seattle was about lower due to isostatic depression from the weight of the glacier. However, the rapid sea level rise from the end of the
Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
through the early
Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...
had flooded the Duwamish Valley and Lake Washington within a couple thousand years. Lake Washington did not become a freshwater lake, isolated from Puget Sound, until some time after 5,700 years
Before Present Before Present (BP) or "years before present (YBP)" is a time scale used mainly in archaeology, geology, and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because ...
, when sedimentation in the Duwamish Valley closed off its southern end. The new lake, lacking any other outlets, drained south through the Black River into the Duwamish Valley and, ultimately, Puget Sound until the construction of the Lake Washington Ship Canal in 1916.


Creeks and rivers

The main inflowing rivers are the Sammamish and Cedar Rivers, with the Cedar supplying most of the water. Seasonal changes in the flow of the Sammamish are moderated by a
weir A weir or low-head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the water level. Weirs are also used to control the flow of water for outlets of l ...
at the Lake Sammamish inlet. The lake is drained by the Lake Washington Ship Canal. In addition, there are numerous small creeks and rivers which feed the lake, including: * Coal Creek * Denny Creek ( O.O. Denny Park) * Fairweather Creek * Forbes Creek * Juanita Creek * Kelsey Creek * Little Creek * Lyon Creek * Mapes Creek * May Creek * McAleer Creek * Mercer Slough * Ravenna Creek * Taylor Creek * Thornton Creek * Yarrow Creek * Yesler Creek Historically, construction of the Lake Washington Ship Canal drastically changed the inflow and outflow of the lake. Before construction of the canal in 1916, Lake Washington's outlet was the Black River, which joined the Duwamish River and emptied into
Elliott Bay Elliott Bay is a part of the Central Basin region of Puget Sound. It is in the U.S. state of Washington, extending southeastward between West Point in the north and Alki Point in the south. Seattle was founded on this body of water in the 1850s ...
. When the canal was opened the level of the lake dropped nearly . The canal became the lake's sole outlet, causing the Black River to dry up and disappear. Before construction, the Sammamish River was the primary source of water for Lake Washington, and the lowering of the lake slightly increased its flow. As part of the ship canal project, the Cedar River was diverted into Lake Washington to become the lake's primary source.


Infrastructure


Canal

The Montlake Cut, part of the Lake Washington Ship Canal, connects the lake to Lake Union and ultimately
Puget Sound Puget Sound ( ; ) is a complex estuary, estuarine system of interconnected Marine habitat, marine waterways and basins located on the northwest coast of the U.S. state of Washington (state), Washington. As a part of the Salish Sea, the sound ...
.


Bridges

Three concrete floating bridges cross Lake Washington: Evergreen Point Floating Bridge ( SR 520), Lacey V. Murrow Memorial Bridge (
I-90 Interstate 90 (I-90) is an east–west transcontinental freeway and the longest Interstate Highway in the United States at . It begins in Seattle, Washington, and travels through the Pacific Northwest, Mountain states, Mountain West, Great Pla ...
eastbound), and Homer M. Hadley Memorial Bridge (
I-90 Interstate 90 (I-90) is an east–west transcontinental freeway and the longest Interstate Highway in the United States at . It begins in Seattle, Washington, and travels through the Pacific Northwest, Mountain states, Mountain West, Great Pla ...
westbound). The floating design is because Lake Washington's depth and muddy bottom prevented the emplacement of the pilings or towers necessary for the construction of a
causeway A causeway is a track, road or railway on the upper point of an embankment across "a low, or wet place, or piece of water". It can be constructed of earth, masonry, wood, or concrete. One of the earliest known wooden causeways is the Sweet T ...
or
suspension bridge A suspension bridge is a type of bridge in which the deck (bridge), deck is hung below suspension wire rope, cables on vertical suspenders. The first modern examples of this type of bridge were built in the early 1800s. Simple suspension bridg ...
. The bridges consist of hollow concrete pontoons that float atop the lake, anchored with cables to each other and to weights on the lake bottom. The roadway is constructed atop these concrete pontoons. Additionally, the East Channel Bridge carries
Interstate 90 Interstate 90 (I-90) is an east–west transcontinental freeway and the longest Interstate Highway in the United States at . It begins in Seattle, Washington, and travels through the Pacific Northwest, Mountain states, Mountain West, Great Pla ...
from Mercer Island to Bellevue. The Evergreen Point Floating Bridge (officially the SR 520 Albert D. Rosellini Evergreen Point Floating Bridge) carries State Route 520 from Seattle's Montlake neighborhood to
Medina Medina, officially al-Madinah al-Munawwarah (, ), also known as Taybah () and known in pre-Islamic times as Yathrib (), is the capital of Medina Province (Saudi Arabia), Medina Province in the Hejaz region of western Kingdom of Saudi Arabia, ...
. The bridge opened in April 2016 and replaced the original Evergreen Point Floating Bridge at the site, which opened in 1963. The 7,710-foot-long (2,350 m) floating span is the longest floating bridge in the world, as well as the world's widest measuring 116 feet (35 m) at its midpoint. The Lacey V. Murrow Memorial Bridge carries
Interstate 90 Interstate 90 (I-90) is an east–west transcontinental freeway and the longest Interstate Highway in the United States at . It begins in Seattle, Washington, and travels through the Pacific Northwest, Mountain states, Mountain West, Great Pla ...
eastbound from Seattle's Mount Baker neighborhood to Mercer Island. Originally opened in 1940, a portion of the Lacey V. Murrow Bridge sank during a windstorm on November 25, 1990. At the time, the bridge was closed for renovations. A Washington State Department of Transportation (WSDOT) investigation revealed that the incident resulted from the improper handling of hydrodemolition water being used during the renovation, rather than in any basic flaw in the bridge's concept or design. The bridge was subsequently rebuilt and reopened in 1993. The Murrow Bridge is the second-longest floating bridge in the world, at 6,620 ft (2,020 m). The Third Lake Washington Bridge (officially the Homer M. Hadley Memorial Bridge) carries the westbound lanes of
Interstate 90 Interstate 90 (I-90) is an east–west transcontinental freeway and the longest Interstate Highway in the United States at . It begins in Seattle, Washington, and travels through the Pacific Northwest, Mountain states, Mountain West, Great Pla ...
and two tracks of Sound Transit's 2 Line between Mercer Island and
Seattle Seattle ( ) is the most populous city in the U.S. state of Washington and in the Pacific Northwest region of North America. With a population of 780,995 in 2024, it is the 18th-most populous city in the United States. The city is the cou ...
. The first pontoon for the new bridge was floated in September 1983, and opened in June 1989. The floating bridge is the fifth-longest of its kind in the world, at 5,811 feet (1,772 m).


Steamboats and ferries

Steamboats and ferries operated on the lake from about 1875 to 1951. In 1892, John L. Anderson started to ferry between Leschi Park and
Newcastle Newcastle usually refers to: *Newcastle upon Tyne, a city and metropolitan borough in Tyne and Wear, England, United Kingdom *Newcastle-under-Lyme, a town in Staffordshire, England, United Kingdom *Newcastle, New South Wales, a metropolitan area ...
on the steamer ''Winnifred''. ''Winnifred'' burned in 1894, but Anderson soon launched a fleet of several ships operated by the Anderson Steamboat Company. In 1913, the Port Commission of Seattle launched the steel-hulled steam ferry '' Leschi'', undercutting Anderson's operations and he eventually went out of business in 1917. The public ferries continued operations until 1950, approximately one year after the tolls were removed from the Murrow bridge.


Shoreline cities and towns

The cities and towns bordering the lake, going clockwise from the west, are
Seattle Seattle ( ) is the most populous city in the U.S. state of Washington and in the Pacific Northwest region of North America. With a population of 780,995 in 2024, it is the 18th-most populous city in the United States. The city is the cou ...
, Lake Forest Park, Kenmore, Kirkland, Yarrow Point, Hunts Point,
Medina Medina, officially al-Madinah al-Munawwarah (, ), also known as Taybah () and known in pre-Islamic times as Yathrib (), is the capital of Medina Province (Saudi Arabia), Medina Province in the Hejaz region of western Kingdom of Saudi Arabia, ...
, Bellevue, Beaux Arts Village, and Renton. The city of Mercer Island occupies the island of the same name, in the southern half of the lake.


Water purity

Around 1900, Seattle began discharging sewage into Lake Washington. During the 1940s and 1950s, eleven sewage treatment plants were sending state-of-the-art treated water into the lake at a rate of 20 million gallons per day. At the same time, phosphate-based detergents came into wide use. The lake responded to the massive input of nutrients by developing unpleasant blooms of noxious blue-green algae (
cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...
). The water lost its clarity, the desirable fish populations declined, and masses of dead algae accumulated on the shores of the lake. After significant pollution, the October 5, 1963 issue of the '' Post Intelligencer'' referred to the lake as "Lake Stinko". Citizen concern led to the creation of a system that diverted the treatment-plant effluents into nearby Puget Sound, where tidal flushing would mix them with open-ocean water. The diversion was completed in 1968, and the lake responded quickly. The algal blooms diminished, the water regained its clarity, and by 1975, recovery was complete. Careful studies by a group of
limnologist Limnology ( ; ) is the study of inland aquatic ecosystems. It includes aspects of the biological, chemical, physical, and geological characteristics of fresh and saline, natural and man-made bodies of water. This includes the study of lakes, ...
s from the
University of Washington The University of Washington (UW and informally U-Dub or U Dub) is a public research university in Seattle, Washington, United States. Founded in 1861, the University of Washington is one of the oldest universities on the West Coast of the Uni ...
showed that phosphate was the culprit. Since then, Lake Washington has undergone major improvements, drastically improving the ecology and water quality, making the water twice as clear as it was in 1950.


See also

* Mount Baker Crew rowing club * Seafair Cup hydroplane races * Lake Sammamish


Notes


References

{{authority control Washington Washington Seattle metropolitan area