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Flathead Lake

Coordinates:47°54′6″N114°6′15″W/ 47.90167°N 114.10417°W/47.90167; -114.10417
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Flathead Lake
člq̓etkʷ(Kalispel-Pend d'Oreille)
yawuʔnik̓ ʔa·kuq̓nuk(Kutenai)
Location of Flathead Lake in Montana, USA.
Location of Flathead Lake in Montana, USA.
Flathead Lake
Location of Flathead Lake in Montana, USA.
Location of Flathead Lake in Montana, USA.
Flathead Lake
LocationLake/Flatheadcounties,Montana,US
Coordinates47°54′6″N114°6′15″W/ 47.90167°N 114.10417°W/47.90167; -114.10417
TypeMoraine-dammed lake
Primary inflows
Primary outflowsFlathead River
Catchment area8,587 sq mi (22,240 km2)
BasincountriesUnited States
Max. length27.3 mi (43.9 km)[1]
Max. width15.5 mi (24.9 km)[1]
Surface area197 sq mi (510 km2)[2]
Average depth164.7 ft (50.2 m)
Max. depth370.7 ft (113.0 m)[1]
Water volume5.56 cu mi (23.2 km3)[1]
Residence time3.4 years
Shore length1161.4 mi (259.7 km)[1]
Surface elevation2,894 ft (882 m)
IslandsWild Horse Island;Cromwell, Bird, Bull, Little Bull, Melita, Shelter, Cedar, Mother-in-Law, Dream, Goose, Mary B, Rock Island; Douglas Islands
Settlements7 miles (11 km) south ofKalispell, Montana; Polson, Montana
1Shore length isnot a well-defined measure.

Flathead Lake(Salish:člq̓etkʷ,Kutenai:yawuʔnik̓ ʔa·kuq̓nuk)[3]is a large natural lake in northwestMontana,United States.

The lake is a remnant of the ancient, massive glacial dammed lake,Lake Missoulaof the era of the lastinterglacial.[4]Flathead Lake is a natural lake along the mainline of theFlathead River.It was dammed in 1930 byKerr Damat its outlet on Polson Bay, slightly raising the lake level; the dam generates electricity.[5]The hydroelectric has been owned and operated by theConfederated Salish and Kootenai Tribessince 2015. It is one of the cleanest lakes in the populated world for its size and type.[6]

Geography[edit]

Located in the northwest corner of the state ofMontana,7 miles (11 km) south ofKalispell,it is approximately 30 miles (48 km) long and 16 miles (26 km) wide, covering 197 square miles (510 km2). It is a similar size as Minnesota'sMille Lacs Lake,but smaller thanRed Lake.It is about half the area ofSan Francisco Bay(main bay). It is larger in surface area thanLake Tahoe,but it is much smaller in volume due to Tahoe's depth.[2]Flathead Lake has a maximum depth of 370.7 ft (113.0 m),[1]and an average of 164.7 ft (50.2 m). This makes Flathead Lake deeper than the average depths of theYellow Seaor thePersian Gulf.Flathead Lake is in a scenic part of Montana, 30 miles (48 km) southwest ofGlacier National Parkand is flanked by two scenic highways, which wind along its curving shoreline. On the west side isU.S. Route 93,and on the east, isRoute 35.

Flathead Lake from space, Aug 2018

The lake is bordered on its eastern shore by theMission Mountainsand on the west by theSalish Mountains.The Flathead valley was formed by theglacial dammingof theFlathead Riverand sustains a remarkably mildclimatefor a region located this far north and inland; thePacific Oceanis almost 400 miles (640 km) to the west. The mild climate allows forcherryorchardson the east shore andvineyardsforwineproduction on the west shore. There are alsoapple,pearandplumorchards around the lake as well asvegetables,hay,honey,nursery tree,Christmas tree,sod/turf, andwheatproduction bordering or near the lake.

The lake has an irregularly shaped shoreline and a dozen small islands cover 5.5 square miles (14 km2).Wild Horse Islandis the largest at 2,164 acres (876 ha). Melita Island is a 64-acre (260,000 m2) island on Flathead Lake, located about one-half mile off the west lakeshore. At its highest point Melita is 80 feet (24 m) 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 ofPolson.The island is owned by theMontana Councilof theBoy Scouts of America,and is home toCamp Melita Island,and is used and for other activities; there is a project for woodland rehabilitation run by the Montana Council.[7]There is also a bald eagle reserve which is protected by the Native Americans. Boy Scouts began using the island in the 1940s.[8]

Geology[edit]

Flathead Lake lies at the southern end of a geological feature called theRocky Mountain Trench.Thetrench,which formed with theRocky Mountains,extends north into the southernYukonas a straight, steepvalley,which also holds the headwaters of theColumbia River.During the lastice agethis trench was filled by an enormousglacier.As the glacier moved southward it carved out the trench. The Polson Moraine, near present-dayPolson, Montana,marks the southernmost extent of the glacier during the last ice age and thus is the site of the glacier'sterminal moraine.[9]

Clouds over Flathead Lake inPolson, Montana,as the sun sets

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 thismoraine dam,it began to cut a channel through it. Mostmoraine dammed lakesdrain quickly because water cuts entirely through the moraine. Flathead Lake remained because abedrockhill buried underneath the Polson Moraine prevented the moraine from being completely cut through so the meltwater never completely drained.[9]

At one time, probably when the valley was partially filled by aglacier,the level of Flathead Lake was about 500 feet (150 m) higher and drained through the valley west ofElmo, 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.[citation needed]

Management[edit]

The Flathead River and theSwan River(known also as the Bigfork River where it enters the lake) are the majortributariesof the five tributaries that are within the Flathead Watershed. Numerous small streams flow into the lake, particularly on the wetter east shore.[1]TheSeli’š Ksanka Qlispe’ Dam,formerly known as Kerr Dam and built nearPolson,controls the top 10-foot of the lake (3.0 m), generateshydroelectric power,and provides water forirrigationto support a federal irrigation project in the area.[10]Minimum outflow levels from Flathead Lake are designated by theFederal Energy Regulatory Commission(FERC) and are based on flood risk management, power generation requirements, and biological needs to support aquatic life in river systems.[11]

The lake is downstream ofHungry Horse Damon theSouth Fork Flathead River.[12]The Hungry Horse Dam is managed by theBureau of Reclamationto provide beneficial flow conditions and to provide safe passage for migrating juvenile fish to reach theColumbia River Estuaryand the Pacific Ocean.[13]The Columbia River Technical Management Team makes operational recommendations to the agencies that control federal dams. Made up of representatives from four states, five federal agencies and six tribal nations, it prioritizes fish and wildlife above other system benefits.[14]The Columbia River system has 14 projects that must be operated to meet congressionally authorized purposes.[15]

History[edit]

Once known as "Salish Lake", this body of water was named for theSalish Indians.Early European explorers, likeDavid Thompson,called them the Flathead Indians because of a misinterpretation of earlyNative American sign language.[16]In 1855 the United States (US) made theTreaty of Hellgate,by which it set aside the Flathead Reservation solely for use of the Flathead, encompassing an area including much of Flathead Lake.

The summer of 2023 saw abnormally low water levels.[17]Variations to the Flood Risk Management Plan were approved by the U.S. Army Corp of Engineers in 2024 in response to the continuing dry conditions.[18]

Fauna[edit]

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 inhabited by the nativebull troutandcutthroat trout,as well as the non-nativelake trout,yellow perch,andlake whitefish.Local residents have reported sighting other aquatic fauna in the lake as well, such assturgeonand theFlathead Lake Monster.[19]

The non-nativeopossum shrimp,(Mysis diluviana), were introduced by Montana Department of Fish, Wildlife and Parks in the Flatheaddrainage basinto encourage production of larger kokanee salmon; they migrated into Flathead Lake and have altered the ecosystem.[20]

Fishermen had introduced lake trout 80 years prior[when?]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 abundantkokaneewere extirpated, and native bull and westslope cutthroat trout are imperiled. Predation by Mysis has shiftedzooplanktonandphytoplanktoncommunity 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).[21]

Like the majority of other nonnative species, thelake trout(Salvelinus namaycush) 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 nativebull trout(Salvelinus confluentus).[22]The semi-annual "Mack Days" Lake Trout fishing contest aims to reduce the non-native "Mackinaw trout" or lake trout populations, as well as educate people about the Flathead Lake Fisheries Management Plan.[23][24]Since the inception of this event in 2002, over 402,000 lake trout have been harvested.[25]

  • Native
  1. Cutthroat Trout
  2. Northern Pikeminnow
  3. Bull Trout
  4. Mountain Whitefish
  5. Westslope Cutthroat Trout
  • Nonnative
  1. Brown Trout
  2. Lake Trout
  3. Golden Trout
  4. Yellowstone Cutthroat Trout
  5. Brook Trout
  6. Rainbow Trout
  7. Kokanee Salmon
  8. Northern Pike
  9. Yellow Perch
  10. Largemouth Bass
  11. Smallmouth Bass
  12. Sturgeon (sp)

In addition to these commonly-pursued game fish, the lake is also home to other native species that currently[when?]are not actively managed by government fish and wildlife agencies, including thelongnose sucker(Catostomus catostomus),redside shiner(Richardsonius balteatus), andslimy sculpin(Cottus cognatus).

Panorama[edit]

Flathead Lake at Lakeside with Swan and Mission Range in the background

Notes[edit]

  1. ^abcdefg"Flathead Lake Facts".Flathead Lake Biological Station.University of Montana.RetrievedJuly 18,2023.
  2. ^abVan der Leeden, Frits; Fred Louis Troise; David Keith Todd (1990).The Water Encyclopedia.CRC Press. p. 185.ISBN978-0-87371-120-3.
  3. ^Johnson, Adam N.; Sievert, Regina; Durglo, Michael; et al. (2014)."Indigenous Knowledge and Geoscience on the Flathead Indian Reservation, Northwest Montana: Implications for Place-Based and Culturally Congruent Education"(PDF).Journal of Geoscience Education.62(2): 187–202.Bibcode:2014JGeEd..62..187J.doi:10.5408/12-393.1.S2CID129648399.RetrievedJuly 27,2022.
  4. ^"The Cordilleran Ice Sheet and Missoula Floods".USGS: Glacial Lake Missoula.RetrievedJuly 27,2022.
  5. ^Kerr Dam,PPL MontanaArchived2016-10-16 at theWayback Machine
  6. ^Flathead Lake & Watershed Overview,Flathead LakersArchived2015-03-22 at theWayback Machine
  7. ^"MELITA ISLAND WOODLAND REHABILITATION PROJECT".Montana Council, Boy Scouts of America.n.d.RetrievedJuly 27,2022.
  8. ^"About Melita Island".Archived fromthe originalon May 12, 2008.RetrievedApril 5,2008.
  9. ^abAlt, David D. (2001).Glacial Lake Missoula: And Its Humongous Floods.Mountain Press Publishing. p. 49.ISBN9780878424153.
  10. ^Drew, Micah (April 3, 2024)."Energy Keepers Receives Approval for Flathead Lake Level Variation".Flathead Beacon.RetrievedApril 5,2024.
  11. ^Mepham, Andy (July 13, 2023)."Dam operators: Beginning of pattern of ever-decreasing levels in Flathead River Basin".KPAX News.RetrievedJuly 15,2023.
  12. ^"Reclamation's operation of Hungry Horse Dam"(Press release). Bureau of Reclamation. July 7, 2023.RetrievedJuly 19,2023.
  13. ^"Federal Columbia River Power System Water Management".NOAA Fisheries.May 10, 2022.RetrievedJuly 19,2023.
  14. ^Drew, Micah (July 15, 2023)."Technical Team Rejects Request to Raise Flathead Lake Levels with Hungry Horse Release".Flathead Beacon.RetrievedJuly 19,2023.
  15. ^Baldwin, Matt (March 16, 2024)."Flathead Basin dam operators defend management decisions".Daily Inter Lake.RetrievedMarch 17,2024.
  16. ^Partoll, Albert (1951). "The Flathead-Salish Indian Name in Montana Nomenclature".Montana: The Magazine of Western History.1(1): 37–47.
  17. ^Heston, Kate (November 15, 2023)."Zinke introduces legislation to regulate Flathead Lake water levels".Daily Inter Lake.RetrievedNovember 15,2023.
  18. ^"Corps removes Flathead Lake level restrictions".KECI NBC Montana.May 24, 2024.RetrievedMay 25,2024.
  19. ^Fugleberg, Paul (April 5, 2015)."Flathead Lake sturgeon catch still controversial".Missoulian.RetrievedApril 10,2015.
  20. ^Bosworth, Brendan."How Non-Native Shrimp Transformed The Ecosystem at Montana's Flathead Lake".RetrievedDecember 15,2016.
  21. ^Ellis, B. K.; Stanford, J. A.; Goodman, D.; Stafford, C. P.; Gustafson, D. L.; Beauchamp, D. A.; Chess, D. W.; Craft, J. A.; Deleray, M. A.; Hansen, B. S. (January 3, 2011)."Long-term effects of a trophic cascade in a large lake ecosystem".Proceedings of the National Academy of Sciences.108(3): 1070–1075.Bibcode:2011PNAS..108.1070E.doi:10.1073/pnas.1013006108.PMC3024674.PMID21199944.
  22. ^Ferguson, Jake M.; Taper, Mark L.; Guy, Christopher S.; Syslo, John M. (2012). "Mechanisms of coexistence between nativebull trout(Salvelinus confluentus) and non-native lake trout (Salvelinus namaycush): Inferences from pattern-oriented modeling ".Canadian Journal of Fisheries and Aquatic Sciences.69(4): 755–769.doi:10.1139/f2011-177.
  23. ^Backus, Perry (September 23, 2017)."Fall Mack Days starts this weekend at Flathead Lake".Missoulian.RetrievedSeptember 24,2017.
  24. ^"Lake Trout Fishing".Mack Days.RetrievedSeptember 24,2017.
  25. ^"Lake Trout Biology".Mack Daysm.RetrievedSeptember 24,2017.

References[edit]

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

External links[edit]

Wikimedia Commons has media related toFlathead Lake.
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