Bighorn Lake- 1982 Sedimentation Survey

Blanton, J

Bighorn Lake was surveyed in 1982 to compile field data needed to compute reservoir storage capacity. The data were also used to compute the volume of sediment accumulated in the reservoir since the gates in the dam were closed in 1965. and to determine the sediment distribution characteristics. Sonic depth recording equipment interfaced with an automated survey system was used to run the bathymetric survey. Reservoir capacity was computed from revised contour surface areas determined by means of a width-adjustment method for the upstream portion of the reservoir and by determining loss of contour surface area by sedimentation in the downstream portion. The reservoir capacity is 1.328,360 acre-feet and the surface area is 17,279 acres at EI. 3657.0. Since November 1965. 53,950 acre-feet of sediment has accumulated. resuting in a loss in storage capacity of 3.9 percent. This represents an annual accumulation rate of 3.224 acre-feet or 0.314 acre-foot per square mile.