The lifetime net economic contribution of a dam that is subject to sedimentation is likely to depend on the storage capacity of its reservoir, how fast the capacity is lost to sedimentation, and the cost of ultimate decommissioning of the dam. A model is developed for determining the size of initial reservoir capacity of a dam to maximize lifetime net benefits, while allowing for the possibility of sediment management to extend its useful life, and accounting for dam decommissioning costs incurred when this life ends. The model is applied to a proposed hydropower dam. Baseline results are compared with those obtained from building the dam at its designed reservoir capacity. Sensitivity analysis with respect to key economic and technical parameters is also carried out to characterize differences in solutions to the cases with and without sediment management. The overall goal is to improve our understanding of optimal dam sizing under different circumstances.

Accumulation of sediment from upstream agricultural land may shorten the lifetime of a reservoir and reduce its long-term benefits. This paper presents a framework for assessment of management strategies that simultaneously considers upstream soil conservation and downstream reservoir-level sediment control. A dynamic model that utilizes optimal control theory is developed for this purpose. Simulation results from the model are expected to provide practical information for policy makers, such as determination of the best sediment removal technology, the optimal timing to install this technology, and the optimal pattern of soil conservation efforts. An illustrative application to Lake Aswan, which is located between the Sudan and Egypt, indicates that the highest permissible level of soil conservation and the unconstrained dredging installed at 22 years are the best management practices, giving a sustainable life of the reservoir and net benefits of $117.8 billion. The cooperative strategy compared...