Upper Stillwater Reservoir is a large high mountain reservoir on the south slope of the High Uintas in Duchesne County, Utah. The reservoir is part of the Central Utah Project. The reservoir was created in 1987 by the construction of a concrete gravity dam (Upper Stillwater Dam). The architecture of the rolled concrete dam is an attraction for engineers. The reservoir elevation is 8,176 ft, and the mean depth is 103.5 ft. Available fish species include rainbow, brown, and brook trout.