lake "Dog Lake", after obtaining nine dogs from the local Klamaths for food. They explored the lake and the Klamath River headwaters, helped by native guides. However, they did not stay in the area for long, instead moving south to tributaries of the Klamath River in search of beaver. Animosity between American immigrants and Native Americans led to armed conflicts. In 1846, a military expedition led by John C. Frémont and Kit Carson were attacked by Native American warriors near Upper Klamath Lake. In revenge, Frémont and Carson's party attacked a local village, killing fourteen people. As more settlers entered the region, the Modoc people resisted by raiding parties along the South Emigrant Trail, which passed through the Klamath River Valley south of Upper Klamath Lake. In 1873, the Native Americans were defeated in the Modoc War, and were relocated to a reservation on the north side of the lake. Being naturally eutrophic, the lake has been known since early times for its poor water quality. Frémont noted the "often foul smelling waters" of the lake, and the Applegate Trail was purposely routed away from the lake because the water was "so bad that it might be too dangerous for livestock to drink late in the season". Starting in the mid-1800s, the valleys both north and south of Upper Klamath were settled and developed for agriculture. Since 1917, the water level in the lake has been regulated by the United States Bureau of Reclamation (BOR)'s Link River Dam as part of the Klamath Reclamation Project, to supply irrigation waters to support agriculture in the upper Klamath Basin. The original timber crib dam was replaced by a more permanent concrete structure in 1921. Ecology Prior to the 20th century, the lake was surrounded by widespread marshes and wetlands, which supported fish, birds and wildlife, as well as protecting water quality in the lake. Much of these important habitats were drained to be converted to cultivated farmland, as farmers did not understand the value of the wetlands for the environment. The lake is naturally eutrophic, due to a high concentration of nutrients. In the 20th century, the augmentation of nutrients by agricultural runoff from the surrounding farming valley has caused the lake to become hypereutrophic, resulting in blue-green algae blooms over the lake ( largely Aphanizomenon flos-aquae). The algae blooms turn the water an opaque green in the summer and reduce the