Reynolds Creek Experimental Watershed
Development of Reynolds Creek Experimental Watershed (RCEW) began in 1960 to support research addressing issues of water supply, seasonal snow, soil freezing, water quality, and rangeland hydrology in the semiarid rangelands of the interior Pacific Northwest. The 239 km2 Reynolds Creek Experimental Watershed is located in the Owyhee Mountains of southwestern Idaho, approximately 80 km southwest of Boise, ID. Field field instrumentation was designed to encompass the spatial complexity of topography, climate and vegetation of a mountainous rangeland watershed. The measurement program was planned for long time series to encompass temporal variability in climate, weather and hydrologic regime.
Reynolds Creek flows almost directly north from the northern flank of the Owyhee Mountains, and is a direct tributary of the Snake River. The Outlet weir, which defines the 239 km² Reynolds Creek Experimental Watershed, is located in a narrow canyon about 11 km south of the confluence of Reynolds Creek and the Snake River. The southwestern sector of RCEW is the coolest and wettest portion of the basin, while the northeastern sector, which includes Summit Wash and Flats watersheds, is the warmest and receives the least precipitation.
The vegetation of RCEW is almost entirely sagebrush rangeland (95%). Plant communities are representative of desert, foothill, and high mountain rangelands found throughout northwestern United States. The major grass species are cheatgrass, bluebunch wheatgrass, bottlebrush squirreltail sandberg bluegrass, and Idaho fescue. The dominant shrubs are big sagebrush, low sagebrush, bitterbrush, and rabbitbrush. Significant stands of coniferous forest are found only in the extreme southern (highest) sectors of RCEW. Approximately two percent of the area is covered by small stands of Douglas fir, aspen, and alpine fir, and three percent of the area is flood- irrigated pastureland.
RCEW is developed in an eroded structural basin in which late Tertiary volcanic and sedimentary rocks overlie Cretaceous granitic basement rocks. The primary geologic formations are granitics of the Idaho Batholith, Salmon Creek volcanics, the Reynolds Basin group complex of basaltic flows, silicic tuff, diatomite, arkosic sand and gravel, and latite, and rhyolitic welded ash flow tuffs.
The soils of RCEW include eight soil associations and 32 soil series. Major soil associations in RCEW include Bakeoven-Reywat-Babbington (35% by area), Harmehl-Gabica-Demast (25% of the watershed), and Nannyton-Larimer-Ackmen, Dark-Gray Variant (12% by area).
The Reynolds Creek Valley, located adjacent to the Silver City mining district, has a long and interesting history. The creek was named after John Reynolds, one of the members of a prospecting party in that area in 1863, when the first settlers established the Carson Ranch. Other ranchers soon followed, who provided meat and vegetables to the 6,000 mining inhabitants several miles to the south. A townsite called Reynolds was located in the center of the valley. The opening of the Reynolds Segment of the Skinner Toll Road from Jordan Valley in Oregon completed the Sacremento, California, to Boise, Idaho, wagon road. Much of the old roadbed is still visible and parts of it are heavily used by present day traffic in the upper Reynolds Creek Valley. Because of the demand for mining timbers, most of the original forest stands were removed from the watershed. As the mining activity began to decrease in the late 1800's and the ranchers increased grazing, by 1900 overgrazing was commonplace and the forest stands nearly depleted. The vegetation was changed considerably. Most of the open range has not recovered from these past practices.