Bedrock Creek Watershed
Physical and Biological Characteristics
Bedrock Creek watershed (24,650 acres) is located in Nez Perce and Clearwater counties, with the lower half of the watershed entirely within the Nez Perce Reservation. The stream is a third order tributary to the Clearwater River, flowing south-easterly to the confluence, 10 miles upstream of the junction of State Highway 3 and US Highway 12 (River Mile 20). Bedrock Creek is approximately 12.69 miles in length with the lower 3 miles located on the Reservation. The watershed contains rolling plateau and steep canyon. Elevations range from 4,140 feet at Teaken Butte to 870 feet at the confluence with the Clearwater River.
Louse Creek (10,479 acre watershed) is 5.2 miles in length and a major tributary to Bedrock Creek. The upper one mile of Louse Creek flows through a steep canyon, and the remaining four miles flow through the plateau region. Other first and second order streams one to three miles in length drain the plateau and flow into main-stem Bedrock Creek.
Bedrock Creek watershed is predominantly underlain by wind -blown loess, Columbia River Plateau basalt flows and course textured alluvium. To a lesser extent the drainage is also underlain by highly weathered Belt Supergroup schist and gneiss and highly weathered Granitics of the Idaho Batholith.
Average precipitation for the region is 25 inches with the majority occurring in October through March. Peak runoff events generally occur in the spring with heavy rains brought by the southwesterly Chinook winds. The rains fall on frozen, exposed soils in the plateau region and on steep slopes, often resulting in sheet and rill erosion. These events contribute to the “flashy” nature of runoff events that are characteristic of the Palouse Region of Idaho. Summer flows may diminish to periods of limited or zero discharge in the upper watershed as soil moisture and depth of soil percolation decreases.
Pre-settlement land cover consisted of grasses (e.g. Bluebunch wheatgrass/Idaho fescue) and a variety of tree species (e.g. Grand fir, Douglas fir, Ponderosa pine, Western red cedar, willow, birch, cottonwood, and alder). The loss of tree cover and the change to predominantly dryland crops in the headwaters has resulted in higher spring flows, a decrease in groundwater recharge, and lower summer flows.
The dominant land use in Bedrock Creek watershed is crops (63%), with the remaining acres used for timber (26%), and pasture (7%). In Louse Creek, the dominant land use in the upper watershed is dryland farming (approximately 5,600 acres or 70%) with the remaining acres used for range and timber (30%). The small community of Cavendish is located in the upper watershed.
Bedrock Creek has been identified as the second most important Clearwater River spawning tributary for steelhead, salmon, and trout. Bedrock Creek also supports a wild population of steelhead (USDA 1992).
Studies, Plans and Reports
Bedrock Creek Watershed Plan – Environmental Assessment (September 1992)
United States Department of Agriculture, Soil Conservation Service
Bedrock Creek Nez Perce/Clearwater Counties, Idaho Water Quality Status Report #63 (1985)
Idaho Department of Health & Welfare, Division of Environment, Boise, Idaho