Flathead Lake ( fla, člq̓etkʷ, label=

Salish Salish () may refer to: * Salish peoples, a group of First Nations/Native Americans ** Coast Salish peoples, several First Nations/Native American groups in the coastal regions of the Pacific Northwest ** Interior Salish peoples, several First Nat ...

, kut, yawuʔnik̓ ʔa·kuq̓nuk) is a large natural lake in northwest

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...

. The lake is a remnant of the ancient, massive glacial dammed lake,

Lake Missoula Lake Missoula was a prehistoric proglacial lake in western Montana that existed periodically at the end of the last ice age between 15,000 and 13,000 years ago. The lake measured about and contained about of water, half the volume of Lake Mic ...

of the era of the last interglacial. Flathead Lake is a natural lake along the mainline of the

Flathead River The Flathead River ( fla, label= Salish, člq̓etkʷ ntx̣ʷetkʷ, , kut, kananmituk), in the northwestern part of the U.S. state of Montana, originates in the Canadian Rockies to the north of Glacier National Park and flows southwest into Fla ...

. It was dammed in 1930 by

Kerr Dam The Seli’š Ksanka Qlispe’ Dam previously known as the Kerr Dam is a concrete gravity-arch dam located at river mile 72 of the Flathead River (116 river kilometer). Built in 1938, it raises the level and increases the size of Flathead Lake ne ...

at its outlet on Polson Bay, slightly raising the lake level; the dam generates electricity.Kerr Dam
PPL Montana The hydroelectric has been owned and operated by the Confederated Salish and Kootenai Tribes since 2015. It is one of the cleanest lakes in the populated world for its size and type.Flathead Lake & Watershed Overview
Flathead Lakers

Geography

Located in the northwest corner of the state of

, south of Kalispell, it is approximately long and wide, covering . It is a similar size as Minnesota's

Mille Lacs Lake Mille Lacs Lake (also called Lake Mille Lacs or Mille Lacs) is a large but shallow lake in the U.S. state of Minnesota. It is located in the counties of Mille Lacs, Aitkin, and Crow Wing, roughly 75 miles north of the Minneapolis-St. Paul m ...

, but smaller than Red Lake. It is about half the area of

San Francisco Bay San Francisco Bay is a large tidal estuary in the U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the big cities of San Francisco, San Jose, and Oakland. San Francisco Bay drains water from a ...

(main bay). It is larger in surface area than

Lake Tahoe Lake Tahoe (; was, Dáʔaw, meaning "the lake") is a Fresh water, freshwater lake in the Sierra Nevada (U.S.), Sierra Nevada of the United States. Lying at , it straddles the state line between California and Nevada, west of Carson City, Nevad ...

, but it is much smaller in volume due to Tahoe's depth. Flathead Lake has a maximum depth of ,About Flathead Head
Flathead Lake Biological Station, The University of Montana and an average of . This makes Flathead Lake deeper than the average depths of the

Yellow Sea The Yellow Sea is a marginal sea of the Western Pacific Ocean located between mainland China and the Korean Peninsula, and can be considered the northwestern part of the East China Sea. It is one of four seas named after common colour terms ...

or the

Persian Gulf The Persian Gulf ( fa, خلیج فارس, translit=xalij-e fârs, lit=Gulf of Persis, Fars, ), sometimes called the ( ar, اَلْخَلِيْجُ ٱلْعَرَبِيُّ, Al-Khalīj al-ˁArabī), is a Mediterranean sea (oceanography), me ...

. Flathead Lake is in a scenic part of Montana, southwest of Glacier National Park and is flanked by two scenic highways, which wind along its curving shoreline. On the west side is U.S. Route 93, and on the east, is Route 35. Flathead Lake by Sentinel-2

The lake is bordered on its eastern shore by the

Mission Mountains The Mission Mountains or Mission Range are a range of the Rocky Mountains located in northwestern Montana in the United States. They lie chiefly in Lake County and Missoula County and are south and east of Flathead Lake and west of the Swan Ra ...

and on the west by the

Salish Mountains The Salish Mountains are located in the northwest corner of the U.S. State of Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota ...

. The Flathead valley was formed by the glacial damming of the

and sustains a remarkably mild

climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologic ...

for a region located this far north and inland; the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

is almost to the west. The mild climate allows for cherry

orchard An orchard is an intentional plantation of trees or shrubs that is maintained for food production. Orchards comprise fruit- or nut-producing trees which are generally grown for commercial production. Orchards are also sometimes a feature of larg ...

s on the east shore and

vineyard A vineyard (; also ) is a plantation of grape-bearing vines, grown mainly for winemaking, but also raisins, table grapes and non-alcoholic grape juice. The science, practice and study of vineyard production is known as viticulture. Vineyards ...

s for

wine Wine is an alcoholic drink typically made from fermented grapes. Yeast consumes the sugar in the grapes and converts it to ethanol and carbon dioxide, releasing heat in the process. Different varieties of grapes and strains of yeasts are m ...

production on the west shore. There are also

apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple fruit tree, trees are agriculture, cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, wh ...

pear Pears are fruits produced and consumed around the world, growing on a tree and harvested in the Northern Hemisphere in late summer into October. The pear tree and shrub are a species of genus ''Pyrus'' , in the family Rosaceae, bearing the p ...

and plum orchards around the lake as well as

vegetable Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still commonly used and is applied to plants collectively to refer to all edible plant matter, including the flowers, fruits, stems, ...

hay Hay is grass, legumes, or other herbaceous plants that have been cut and dried to be stored for use as animal fodder, either for large grazing animals raised as livestock, such as cattle, horses, goats, and sheep, or for smaller domesticat ...

honey Honey is a sweet and viscous substance made by several bees, the best-known of which are honey bees. Honey is made and stored to nourish bee colonies. Bees produce honey by gathering and then refining the sugary secretions of plants (primar ...

, nursery tree,

Christmas tree A Christmas tree is a decorated tree, usually an evergreen conifer, such as a spruce, pine or fir, or an artificial tree of similar appearance, associated with the celebration of Christmas. The custom was further developed in early modern ...

sod Sod, also known as turf, is the upper layer of soil with the grass growing on it that is often harvested into rolls. In Australian and British English, sod is more commonly known as ''turf'', and the word "sod" is limited mainly to agricult ...

/turf, and

wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...

production bordering or near the lake. There are several islands in the lake. Wild Horse Island is the largest at . Melita Island is a island on Flathead Lake, located about one-half mile off the west lakeshore. At its highest point Melita is above water level. The closest access is from Walstad Landing (one and a half miles), a state-maintained landing off Highway 93, approximately 15 minutes north of Polson. The island is owned by the Montana Council of the

Boy Scouts of America The Boy Scouts of America (BSA, colloquially the Boy Scouts) is one of the largest scouting organizations and one of the largest youth organizations in the United States, with about 1.2 million youth participants. The BSA was founded i ...

, and is home to Camp Melita Island, and is used and for other activities; there is a project for woodland rehabilitation run by the Montana Council. There is also a bald eagle reserve which is protected by the Native Americans. Boy Scouts began using the island in the 1940s.

History

Once known as "Salish Lake", this body of water was named for the Salish Indians. Early European explorers, like David Thompson, called them the Flathead Indians because of a misinterpretation of early Native American sign language. A common misconception is that the name is derived from a practice of

head flattening Artificial cranial deformation or modification, head flattening, or head binding is a form of body alteration in which the skull of a human being is deformed intentionally. It is done by distorting the normal growth of a child's skull by applying ...

more common among tribes such as the Chinook. There is no evidence to show that the

ever had this custom. Since the late 19th century, the Salish were mostly removed to the

Flathead Indian Reservation The Flathead Indian Reservation, located in western Montana on the Flathead River, is home to the Bitterroot Salish, Kootenai, and Pend d'Oreilles tribes – also known as the Confederated Salish and Kootenai Tribes of the Flathead Nation. The ...

, located at the southern end of the lake. The Seli’š Ksanka Qlispe’ Dam, built near Polson, regulates the lake's water level, generates

hydroelectric power Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined an ...

, and provides water for

irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...

to support agriculture in the area. The lake has an irregularly shaped shoreline and a dozen small islands, the largest of which is a state park called Wild Horse Island. These islands cover . The

and the Swan River (known also as the Bigfork River where it enters the lake) are the lake's major

tributaries A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drainag ...

. The lake is inhabited by the native

bull trout The bull trout (''Salvelinus confluentus'') is a char of the family Salmonidae native to northwestern North America. Historically, ''S. confluentus'' has been known as the " Dolly Varden" (''S. malma''), but was reclassified as a separate speci ...

and

cutthroat trout The cutthroat trout is a fish species of the family Salmonidae native to cold-water tributaries of the Pacific Ocean, Rocky Mountains, and Great Basin in North America. As a member of the genus '' Oncorhynchus'', it is one of the Pacific tro ...

, as well as the non-native

lake trout The lake trout (''Salvelinus namaycush'') is a freshwater char living mainly in lakes in northern North America. Other names for it include mackinaw, namaycush, lake char (or charr), touladi, togue, and grey trout. In Lake Superior, it can also ...

yellow perch The yellow perch (''Perca flavescens''), commonly referred to as perch, striped perch, American perch, American river perch or preacher is a freshwater perciform fish native to much of North America. The yellow perch was described in 1814 by Samu ...

, and

lake whitefish The lake whitefish (''Coregonus clupeaformis'') is a species of freshwater whitefish from North America. Lake whitefish are found throughout much of Canada and parts of the northern United States, including all of the Great Lakes. The lake white ...

. Local residents have reported sighting other aquatic fauna in the lake as well, such as

sturgeon Sturgeon is the common name for the 27 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretace ...

and the Flathead Lake Monster. The non-native

opossum shrimp Mysida is an order of small, shrimp-like crustaceans in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch or "marsupium" in females. The fact that the larvae are reared in ...

, (''Mysis diluviana''), were introduced by Montana Department of Fish, Wildlife and Parks in the Flathead drainage basin to encourage production of larger kokanee salmon; they migrated into Flathead Lake and have altered the ecosystem. Fishermen had introduced lake trout 80 years prior but remained at low densities until the non-native Mysis became established. The bottom-dwelling mysids eliminated a recruitment bottleneck for lake trout by providing a deep water source of food where little was available previously. Lake trout subsequently flourished on mysids; this voracious piscivore now dominates the lake fishery. The formerly abundant kokanee were extirpated, and native bull and westslope cutthroat trout are imperiled. Predation by Mysis has shifted

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

and

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. Ph ...

community size structure. Bayesian change point analysis of primary productivity (27-y time series) showed a significant step increase of 55 mg C m−2 d−1 (i.e., 21% rise) concurrent with the mysid invasion, but little trend before or after despite increasing nutrient loading. Mysis facilitated predation by lake trout and indirectly caused the collapse of kokanee, redirecting energy flow through the ecosystem that would otherwise have been available to other top predators (bald eagles).

Geology

Flathead Lake lies at the southern end of a geological feature called the Rocky Mountain Trench. The

trench A trench is a type of excavation or in the ground that is generally deeper than it is wide (as opposed to a wider gully, or ditch), and narrow compared with its length (as opposed to a simple hole or pit). In geology, trenches result from ero ...

, which formed with the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...

, extends north into the southern

Yukon Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...

as a straight, steep

valley A valley is an elongated low area often running between Hill, hills or Mountain, mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers ...

, which also holds the headwaters of the

Columbia River The Columbia River (Upper Chinook: ' or '; Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, C ...

. During the last

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gree ...

this trench was filled by an enormous

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...

. As the glacier moved southward it carved out the trench. The Polson Moraine, near present-day

Polson, Montana Polson (Montana Salish: nčmqnétkʷ, Kutenai: kwataqnuk) is a city in Lake County, Montana, United States, on the southern shore of Flathead Lake. It is also on the Flathead Indian Reservation. The population was 5,148 at the 2020 census. It ...

, marks the southernmost extent of the glacier during the last ice age and thus is the site of the glacier's

terminal moraine A terminal moraine, also called end moraine, is a type of moraine that forms at the terminal (edge) of a glacier, marking its maximum advance. At this point, debris that has accumulated by plucking and abrasion, has been pushed by the front edge ...

The large size of the Polson Moraine indicates that the glacier stalled here for many years before retreating. As the climate warmed, a portion of the glacier in the Mission Valley receded more slowly than the main body, which kept the lake basin from being filled with sediment. Eventually this ice also melted, forming a lake behind the moraine. Once the water reached the top of this moraine dam, it began to cut a channel through it. Most

moraine dammed lake A moraine-dammed lake occurs when the terminal moraine has prevented some meltwater from leaving the valley. Its most common shape is that of a long ribbon (ribbon lake). Example of moraine dammed lakes include: *Argentina/Chile: General Carre ...

s drain quickly because water cuts entirely through the moraine. However, Flathead Lake remains because a

bedrock In geology, bedrock is solid Rock (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface mater ...

hill buried underneath the Polson Moraine prevented the moraine from being completely cut through so the meltwater never completely drained. At one time, probably when the valley was partially filled by a

, the level of Flathead Lake was about higher and drained through the valley west of Elmo, Montana, which is at the end of Big Arm Bay, bottom center in the aerial photo above. Water carved out a wide, flat-bottomed pass with a deeper, narrow channel at the south edge of the pass. The deeper channel and traces of the dry riverbed are still visible from Route 28.

Fish

Flathead Lake is home to a number of native and non-native fishes, and is managed cooperatively by both Montana Fish, Wildlife and Parks and the Confederated Salish and Kootenai Tribes. The lake is home to the semi-annual "Mack Days" Lake Trout fishing contest, which aims to reduce the non-native "Mackinaw trout" or

(''Salvelinus namaycush'') populations, as well as educate people about the Flathead Lake Fisheries Management Plan. Like the majority of other nonnative species, they became established in the lake from the late 1800s-early 1900s. The introduction of lake trout has placed increased pressure on the ecologically similar threatened native

(''Salvelinus confluentus''). Since the inception of this event in 2002, over 402,000 lake trout have been harvested. Another recent introduced non-native fish is the Dodd Fish, another name for

(''Perca flavescens''). *Native #

Cutthroat Trout The cutthroat trout is a fish species of the family Salmonidae native to cold-water tributaries of the Pacific Ocean, Rocky Mountains, and Great Basin in North America. As a member of the genus '' Oncorhynchus'', it is one of the Pacific tro ...

#Northern Pikeminnow #

Bull Trout The bull trout (''Salvelinus confluentus'') is a char of the family Salmonidae native to northwestern North America. Historically, ''S. confluentus'' has been known as the " Dolly Varden" (''S. malma''), but was reclassified as a separate speci ...

#Mountain Whitefish #Westslope Cutthroat Trout *Nonnative #

Brown Trout The brown trout (''Salmo trutta'') is a European species of salmonid fish that has been widely introduced into suitable environments globally. It includes purely freshwater populations, referred to as the riverine ecotype, ''Salmo trutta'' morph ...

Lake Trout The lake trout (''Salvelinus namaycush'') is a freshwater char living mainly in lakes in northern North America. Other names for it include mackinaw, namaycush, lake char (or charr), touladi, togue, and grey trout. In Lake Superior, it can also ...

Golden Trout The California golden trout (''Oncorhynchus aguabonita or Oncorhynchus mykiss aguabonita''), is a species of trout native to California. The golden trout is normally found in the Golden Trout Creek (tributary to the Kern River), Volcano Creek (t ...

#Yellowstone Cutthroat Trout #

Brook Trout The brook trout (''Salvelinus fontinalis'') is a species of freshwater fish in the char genus ''Salvelinus'' of the salmon family Salmonidae. It is native to Eastern North America in the United States and Canada, but has been introduced elsewhere ...

Rainbow Trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributaries of the Pacific Ocean in Asia and North America. The steelhead (sometimes called "steelhead trout") is an anadromous (sea-run) form of the coasta ...

Kokanee Salmon The kokanee salmon (''Oncorhynchus nerka''), also known as the kokanee trout, little redfish, silver trout, kikanning, Kennerly's salmon, Kennerly's trout, or Walla, is the non-anadromous form of the sockeye salmon (meaning that they do not migrat ...

Northern Pike The northern pike (''Esox lucius'') is a species of carnivorous fish of the genus '' Esox'' (the pikes). They are typical of brackish and fresh waters of the Northern Hemisphere (''i.e.'' holarctic in distribution). They are known simply as a ...

Yellow Perch The yellow perch (''Perca flavescens''), commonly referred to as perch, striped perch, American perch, American river perch or preacher is a freshwater perciform fish native to much of North America. The yellow perch was described in 1814 by Samu ...

Largemouth Bass The largemouth bass (''Micropterus salmoides'') is a carnivorous freshwater gamefish in the Centrarchidae ( sunfish) family, a species of black bass native to the eastern and central United States, southeastern Canada and northern Mexico, but ...

# Smallmouth Bass #Sturgeon (sp) In addition to these commonly-pursued game fish, the lake is also home to other native species that currently are not actively managed by government fish and wildlife agencies, including the

longnose sucker The longnose sucker (''Catostomus catostomus'') is a species of cypriniform freshwater fish in the family Catostomidae. It is native to North America from the northern United States to the top of the continent. It is also found in Russia in ri ...

(''Catostomus catostomus''),

redside shiner The redside shiner (''Richardsonius balteatus'') is a species of cyprinid fish found in the western United States and Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean ...

(''Richardsonius balteatus''), and

slimy sculpin The slimy sculpin (''Cottus cognatus'') is a freshwater species of fish belonging to the family Cottidae, which is the largest sculpin family. They usually inhabit cold rocky streams or lakes across North America, ranging from the Great Lakes, so ...

(''Cottus cognatus'').

Panorama

Notes

References

* Alt, David. "The Making of Flathead Lake" in ''Profiles of Montana Geology: A layman's guide to the Treasure State''. Butte, MT: Montana Bureau of Mines and Geology, 1984.

External links

Flathead Basin Commission
{{authority control Bodies of water of Lake County, Montana Geology of Montana Lakes of Flathead County, Montana Lakes of Montana Lakes of the Rocky Mountains