Alternatives Study of Willwood Diversion Dam Siltation Removal in Wyoming, USA

Willwood Dam was built in 1924 as a diversion dam for irrigation. It is a run-of-the river reservoir located at a developing point bar in Wyoming, U.S.A. Based on current operating criteria, the release flow is restricted by an allowable turbidity increase of 10 Nephelometric Turbidity Units (NTU) from upstream to downstream of the dam. Currently, two of the three sluice gates have been clogged by siltation. These limited sluicing capacities have increased the sedimentation within the reservoir and the irrigation canal network. In this study, de-siltation alternatives combining dredging, sluicing, and flushing were recommended to achieve the dam's operation goals and restrict sediment accumulation. Three operation curves and three dredging alternatives were used to evaluate sediment flushing/sluicing performances by using GSTARS 3.01 models. This study presents an efficiency analysis of the de-siltation alternatives, the expected operation life, and recommendations for this dam rehabilitation project.