Abstract
The managers of the Bighorn Canyon National Recreation Area have expressed concern about two aspects of water quality in Bighorn Lake, the rate of sediment accumulation in the upper ends of the lake, especially in the Horseshoe Bend region, and the excessive fertility that occurs generally in the upper end, although it sometimes extends throughout the total length of the lake. In the spring of 1980 a cooperative study was initiated which was designed to estimate the rate of sediment accumulation in the Horseshoe Bend area of Bighorn Lake since closure of the Yellowtail Dam in 1967. Studies were also initiated to evaluate the sources of aquatic plant nutrients, the factors limiting phytoplankton growth within the upper ends of Bighorn Lake, and the current degree of eutrophication-fertility of waters in this region of the waterbody. This report presents a summary of the results of the first eight months of these studies.