Upper Klamath Lake (sometimes called Klamath Lake) (Klamath: ?ews, "lake" ) is a large, shallow freshwater lake east of the Cascade Range in south-central Oregon in the United States. The largest body of fresh water by surface area in Oregon, it is approximately long and wide and extends northwest from the city of Klamath Falls. It sits at an average elevation of . In the early 20th century, most of the wetlands and marshes surrounding the lake were drained for agricultural purposes, damaging the larger habitat. The lake's water has been used to support the federal Klamath Project for irrigation by local farmers for a century. The lake depth fluctuates due to regulation of its water supply, averaging between deep. The lake level is kept within above sea level to ensure a viable fishery in the lake and to protect coho salmon in the Klamath River below the lake. Upper Klamath Lake is fed by a watershed of including the Williamson and Wood Rivers, and is drained by the Klamath River (known here as the Link River), which issues from the south end of the lake. The lake is connected by a short channel to the smaller Agency Lake to the north. The Upper Klamath National Wildlife Refuge has been established on land along the northern edge of the lake to preserve natural habitat. Geology Upper Klamath Lake is the largest remnant of Lake Modoc, a giant pluvial lake that existed in the region until about 10,000 years ago. At its largest, Lake Modoc covered over , joining Upper Klamath, Lower Klamath, and Tule Lakes, as well as all of the major wetlands in the upper Klamath River basin, into a contiguous body of water. The lake was more than ten times the size of present-day Upper Klamath Lake and sat nearly higher in elevation. Lake Modoc disappeared at the end of the Pleistocene due to a warming and drying climate. History The region around Upper Klamath Lake and the Williamson, Sprague and Wood rivers to the north of the lake were originally inhabited by the Klamath people. The Modoc people inhabited the lands to the south of Upper Klamath Lake, around the Lower Klamath and Tule lakes. The first recorded persons of European descent to visit Upper Klamath Lake were a party of Hudson's Bay Company fur trappers commanded by Peter Skene Ogden in December 1826. Ogden called the