The economics of using sediment-entrapment reduction measures in lake and reservoir design

One of the most important impacts of building and maintaining a reservoir is the loss of storage capacity caused by sediment deposition behind the dam. Sediment deposition in the reservoir reduces the water storage volume and decreases or even negates the utility of the dam, and deteriorates the water quality. The loss of utility of a reservoir as a result of sedimentation or siltation can be considered an economic, environmental, and even a design failure. The objective of this study was to investigate, through an extensive literature search, the suitability and efficiency of several reservoir sedimentation reduction measures practiced in small- and medium-sized lakes. Some of the methods successfully used for reducing sediment entrapment in reservoirs were watershed management, building check dams, bypassing sediment-laden flows, using density currents, flood flushing, drawdown flushing, flushing and emptying, siphoning, and dredging. The mitigation and operation methods so identified were evaluated with respect to their rate of success, cost, environmental impacts, and ease of implementation or retrofitting. The economies expected in using the identified alternative mitigative measures versus more conventional reservoir design were investigated in terms of reduced initial cost of reservoir and/or dredging costs.U.S. Department of the InteriorU.S. Geological SurveyOpe