Mann Lake is the largest of the shallow playa lakes in the northern part of the Alvord Valley in Harney County in the U.S. state of

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

. The lake is a remnant of a larger

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 ...

lake that covered much of the valley, east of Steens Mountain. Fields–Denio Road runs along the east side of the lake. Inflow to Mann Lake comes from small, intermittent streams, mainly from Steens Mountain. The lake, which has no outlet, but loses water by evaporation, is hypereutrophic. An influx of cattle waste from nearby rangelands adds to the lake's natural eutrophic state. Large concentrations of'' Cladophora'' algae are common. The

Bureau of Land Management The Bureau of Land Management (BLM) is an agency within the United States Department of the Interior responsible for administering federal lands, U.S. federal lands. Headquartered in Washington, D.C., the BLM oversees more than of land, or one ...

operates the Mann Lake Recreation Site, about southeast of

Burns Burns may refer to: Astronomy * 2708 Burns, an asteroid * Burns (crater), on Mercury People * Burns (surname), list of people and characters named Burns ** Burns (musician), Scottish record producer Places in the United States * Burns, ...

by highway and unpaved road. The site has vault restrooms and boat ramps, but no other amenities. Recreation at or near the site includes fishing, camping, hiking, wildlife viewing, and

amateur geology Amateur geology or rock collecting (also referred to as rockhounding in the United States and Canada) is the non-professional study and hobby of collecting rocks and minerals or fossil specimens from the natural environment.Sinkankas, John. Miner ...

. Mann Lake, stocked with Lahontan cutthroat trout, has been called "one of the premiere trout fisheries in southeast Oregon". Trout in the lake range in length from . Fishing is restricted to artificial flies and lures. A large population of

goldfish The goldfish (''Carassius auratus'') is a freshwater fish in the family Cyprinidae of the order Cypriniformes. It is commonly kept as a pet in indoor aquariums, and is one of the most popular aquarium fish. Goldfish released into the w ...

, introduced illegally, have at times multiplied in Mann Lake and competed for food with the smaller trout. In 2010, the

Oregon Department of Fish and Wildlife The Oregon Department of Fish and Wildlife (ODFW) is a state government, government agency of the U.S. state of Oregon responsible for programs protecting Oregon fish and wildlife resources and their habitats. The agency operates hatcheries, i ...

treated the lake with

rotenone Rotenone is an odorless, colorless, crystalline isoflavone. It occurs naturally in the seeds and stems of several plants, such as the jicama vine, and in the roots of several other members of the Fabaceae. It was the first-described member of the ...

, a

piscicide A piscicide is a chemical substance which is poisonous to fish. The primary use for piscicides is to eliminate a dominant species of fish in a body of water, as the first step in attempting to populate the body of water with a different fish. They ...

, killing around 200,000 goldfish and

fathead minnow Fathead minnow (''Pimephales promelas''), also known as fathead or tuffy, is a species of freshwater Actinopterygii, ray-finned fish belonging to the Family (biology), family Leuciscidae, the shiners, daces and minnows. The natural geographic ra ...

s while sparing nearly all the trout.

References

External links

*
Mann Lake Campground
– Public Lands Information Center {{authority control Lakes of Oregon Lakes of Harney County, Oregon Endorheic lakes of Oregon

See also

References

External links