Upper Klamath Lake: The Largest Lake in Oregon

View photos

Upper Klamath Lake (also known simply as Klamath Lake) is a large freshwater lake located in south-central Oregon, United States. It is the largest lake in Oregon by surface area, and has a total length of 40 kilometers (25 miles) and a maximum width of 13 kilometers (8 miles). The city of Klamath Falls is located on the southeastern tip of the lake.

Upper Klamath Lake Stats

Lake NameUpper Klamath Lake
CountryUnited States
Surface area276.630
Maximum depth14.9
Average depth2.3
Lake typeHypereutrophic
Catchment area9583.60
InflowsWilliamson River, Wood River, Crooked Creek, Fourmile Creek
OutflowsLink River
Shore length176.76
Residence time136.3
Trophic stateHypereutrophic
Average discharge54.854

Upper Klamath Lake Accommodation

Geography and Hydrology

Upper Klamath Lake sits at an altitude of 1,260 meters (4,140 feet) in a structural valley known as the Klamath Graben, East of the Cascade Mountains. The depth of the lake fluctuates due to the regulation of its waters. The average depth can range anywhere in between 2.4 meters to 15.2 meters (8 to 50 feet). However, the level of the lake is kept between 1,261 meters and 1,263 meters (4,137 yo 4,143 feet) for 2 main reasons: to maintain a viable fishery in the lake and to protect the coho salmon, which populates the Klamath River below the lake.

The lake’s total watershed (or catchment area) covers a surface area of 9,760 square kilometers (or 3,768 square miles), and much of it is a mountainous volcanic area covered with pumice deposits, which resulted from the formation of the Crater Lake caldera. A small channel connects Upper Klamath Lake to Agency Lake, which is located to the North.

Elevations in the basin of the Upper Klamath Lake can vary from the lake level to more than 2,743 meters (9,000 feet) at some peaks in the Cascade Mountain Range. Precipitation also varies a lot from 15 inches at lower elevations to 60 inches at higher elevations, making vegetation very diverse. Douglas fir, lodgepole pine, ponderosa pine and true firs are present in the mountainous regions, while the open flatlands are occupied by grass-shrub.

The main inflows of Upper Klamath Lake are Williamson River and Wood River, and the main outflow is the Klamath River, which goes out of the lake at its southern tip. Williamson River accounts for 46% of the water inflow into the lake. A large spring feeds Williamson River, which flows through pasture land before it enters the Klamath Marsh, carrying a high concentration of phosphorus. Williamson River also carries dissolved organic matter (humic substances) into the lake, derived from the Klamath Marsh. Sprague River flows into the Williamson River just before the latter enters Upper Klamath Lake at its northern tip.

The lake’s second largest tributary, Wood River, drains into Agency Lake first and then into the Upper Klamath Lake on the northern shore. The main outflow, Klamath River which is known locally as Link River, flows out from the south end of the lake into Lake Ewauna, and ultimately empties into the Pacific Ocean in northern California.

In order to protect the natural habitat around the lake, the Upper Klamath National Wildlife Refuge was established in 1928 along the northern edge of the lake. It covers an area of 61 square kilometers (23 square miles), and mainly comprises freshwater hardstem-cattail marsh and open water, but also 12 hectares of forested uplands. The refuge serves as a great nesting area for waterfowl and colonial nesting birds, such as the American white pelican and several heron species. Bald eagles and ospreys can also sometimes be seen fishing in the refuge waters.

Upper Klamath Lake is hypereutrophic, and has been known for its poor water quality since early times.


Upper Klamath Lake is a remnant of Lake Madoc, which was more than 10 times larger than Upper Klamath Lake. Lake Madoc was a pluvial lake that existed until 10,000 years ago, and covered an area of more than 2,600 square kilometers (1,000 square miles). It used to join Upper Klamath Lake, Lower Klamath Lake, Tule Lakes, and all major wetlands in the upper basin of the Klamath River into a single lake. The lake was also located about 30 meters (100 feet) higher, and it disappeared due to warming and drying climate at the end of the Pleistocene.


The Klamath people originally inhabited the region to the north of the lake, and the Madoc people inhabited the region to the south of the lake.

The first record of Europeans visiting the lake dates from December 1826. The visitors were a party of fur trappers working for the Hudson's Bay Company, and led by Peter Skene Ogden. Helped by native guides, the party explored the lake but didn’t stay in the area for long, heading south in search of beaver.

The area also had its share of armed conflicts triggered by the animosities between Native Americans and immigrants. In 1846, Native Americans attacked a military expedition led by Kit Carson and John C. Frémont, who in turn attacked a local village killing 14 people. The Modoc people resisted the settlers by raiding parties along the South Emigrant Trail. However, they were defeated in 1873 in the Modoc War, and relocated to a reservation in the northern part of the lake.

In the mid-19 century, the valleys north and south of the lake were settled and agriculture development started. The lake’s water level has been regulated by the Link River Dam since 1917. The original timber crib dam was replaced by a concrete gravity dam in 1921, and is owned by the U.S. Bureau of Reclamation. The dam has a height of 7 meters (23 feet).

Most of the wetlands that used to surround the lake were drained in the early 20th century for agricultural purposes, damaging the wildlife and habitat.


Before the 20th century when the marshes and wetlands were drained, the region supported abundant wildlife. The wetlands also used to protect water quality in the Upper Klamath Lake.

Since many of these critical habitats were drained, the lake went from eutrophic to hypereutrophic, due to more nutrients coming to the lake from agricultural runoff. This resulted in blue-green algae blooms on the lake. By turning the water into an opaque green color, these algae blooms reduce recreational activities on the lake.

The dominant alga is Aphanizomenon flos-aquae, a blue-green alga which forms large colonies. It begins to appear in late spring and continues to increase by late summer. In early fall, these algae die, and the decomposition of the large biomass leads to the depletion of dissolved oxygen and unpleasant odors. Another cause for concern is the amount of dissolved oxygen in the lake: the state standards are violated on a regular basis, which means that fish are endangered as well. The hypereutrophic state also leads to an overabundance of midges, which swarm and are a serious nuisance to people around the lake.

In 1988, due to this decline in water quality, the US Fish and Wildlife Service (FWS) put the shortnose sucker and the Lost River sucker, two fish species that used to be abundant in Upper Klamath Lake, on the federal endangered species list. Consequently, a dredging project that would have damaged water quality even more was abandoned by the government.

In the summer of 2001 the entire Oregon was in a drought, which increased environmental concerns about the lake. To protect the sucker population, the BOR stopped withdrawing water from the lake, which resulted in protests from the farming community. Starting with 2003, the FWS monitors the lake regularly because of water shortfalls, which not only endanger fish in the Upper Klamath Lake, but salmon in the Klamath River as well. The future of Upper Klamath Lake is of national interest, because of the conflict between farmers (who are supported by federal subsidies and programs) and environmental groups.

Upper Klamath Lake continues to be an important stop for waterfowl along the Pacific Flyway. The lake is also known for its rainbow trout fishery.


Even with so many ecological problems, Upper Klamath Lake is a beautiful lake and has always been popular among outdoor enthusiasts, especially for fishing and boating. However, because of the poor water quality in the lake, activities that involve water contact are discouraged.

Rainbow trout is the major attraction among anglers, and some very large fish have been caught here. Also some warm water species can be found in the Upper Klamath Lake. Two genera of Cyprinidae, blue chub and tui chub, make up 90% of the fish population in the lake.

Anglers will be happy to know that fishing for trout is allowed in the southern part of the lake during the entire year. However, the northern section of the lake, including Agency Lake, is only open during summer trout season. The western shore of the lake sees much of the fishing, from Pelican Bay to Wocus Bay. The rough waters from farther out into the lake makes fishing mostly limited close to shore.

The lake is also spectacular for canoeing and kayaking enthusiasts, who can follow trails through the marshes and waterways of Pelican Bay. There are also charter tours available that cover the fascinating history, geography, and ecology of the lake.

There’s no shortage of accommodation either: several resorts can be found around the lake, especially on the western shore. There are also many public campgrounds, picnic areas, and boat launches.

Upper Klamath Lake Map