The Williamson River runs roughly 75 miles through southwestern Oregon.
- Resident Rainbow Trout
- Location: Tributary of Klamath Lake
- Length: 100 miles
- Habitat Degradation
- Agricultural Irrigation
The Williamson River
The Williamson River is part of the larger Klamath River watershed and drains approximately 3000 square miles of arid land in this watershed. Within the Winema National Forest sits Fuego Mountain, where the Williamson originates. It flows through the mountains and eventually across the Klamath Marsh National Wildlife Refuge, an important 40,000 acre wildlife habitat. Its main tributary, the Sprague River, joins it just south of Chiloquin. They empty into Upper Klamath Lake a few miles south of town, providing more than half the inflow into the largest freshwater lake in Oregon.
At one time, the Williamson flowed across twelve square miles of rich river delta on the north end of Upper Klamath Lake. Much of this area was drained for agriculture in the ranching valley north of the lake. Bank erosion and loss of fish habitat are the common results from this sort of agricultural activity. The Nature Conservancy has acquired a portion of the delta and has been restoring over 7000 acres of critical wetland.
Wild, Native Fish
The Williamson is known for especially large wild rainbow trout, which move into the river to spawn and to escape Upper Klamath Lake when it gets warm. The Williamson also holds native populations of redband trout. The redband population above the Klamath Marsh is believed to be genetically different from the population below the marsh. They are identified as the upper Williamson River Redband and are indigenous to this river only.