Cooper Creek Reservoir
- Douglas County)
(From Atlas of Oregon Lakes, Johnson et al. 1985). Cooper Creek Reservoir is a long, narrow impoundment which stores the flow of Cooper Creek, a tributary of Sutherlin Creek. The dam is about eight miles upstream from the North Umpqua River. It was built in the late 1960s by the Soil Conservation Service as a multi-purpose water resource project, with primary uses for both municipal supplies and public recreation. The drainage basin is mostly private forest land; the shoreline is also mostly private land, although public access is available on all sides. Douglas County has some shoreline property and has built two picnic areas and two paved boat ramps. Quite a bit of water skiing is done on the reservoir, an activity that conflicts with fishing, although a five mile per hour speed limit is enforced in the fishing areas. Cooper Creek Reservoir is very popular with local anglers and is a good producer of rainbow trout, largemouth bass and crappies. Crappie angling is especially good in the arms of the lake during spring and early summer.
The reservoir is relatively shallow with a mean depth of 23 feet. It is deepest (70 feet) near the dam at the western end and becomes progressively shallower toward the southeast where Cooper Creek enters. Sodium and chloride concentrations are remarkably high, similar to nearby Plat I reservoir. Conductivity is also well above average for southern Oregon reservoirs and there is some evidence of even greater conductivity in water near the bottom of the reservoir (USGS, 1979). This suggests that the reservoir may be somewhat meromictic, or permanently stratified. During summer, the water is sometimes anoxic (depleted of oxygen) below 40 feet. Rooted macrophytes develop in shallow water areas.