Grove Lake Sediment Bypass

Grove Lake, in northeastern Nebraska, traps an average of 1850 to 2466 cubic meter (1.5 to 2 acre-foot) of sediment per year. This has created of a delta in the lake inlet more than 0.4 kilometer (1/4 of a mile) in length. The Nebraska Game and Parks Commission, Fisheries Division applied for and received an Environmental Trust Grant to install a settling basin to reduce siltation of Grove Lake. After review of the quantity of silt entering the lake, available storage area, and available man power to maintain the settling basin, it was determined a settling basin was not feasible. Instead a siphon type sediment bypass was designed and installed in Grove Lake. The bypass is 150 mm (6 inches) in diameter and 1000 meter (3200 foot) in length. The highest point of the siphon is 10 meter (32 foot) above the discharge below the dam that forms Grove Lake. In the summer of 1998 samples of the bed load showed a daily sedimentation rate of 1800 kilograms (two tons) per day. The bypass removes 900 kilograms (one ton) of sediment per day from Verdigre Creek the major creek feeding Grove Lake and discharges the sediment below the dam. The bypass reduced the sedimentation of Grove Lake and is restoring the stream below Grove Lake to pre-dam conditions. Design and installation methods will be described in the following paper, also, problems associated with the starting and maintaining the flow in a siphon of the length and height required to bypass sediment through Grove Lake.