Computer simulation of reservoir sediment management strategies is becoming more important as worldwide water supply shrinks due to sediment deposition, while population growth continues. We identified the physical processes underlying each of the several alternatives available to transport incoming or deposited sediments downstream into receiving waters and the governing equations that describe each process. The purpose of this paper is to understand how physical characteristics of reservoir sediment management can be simulated with available computer codes. We described commonly available computer codes and their abilities to solve the appropriate equations in one, two, or three dimensions. The results revealed that one dimensional models are most appropriate for long-term simulations of the evolving reservoir bottom profile, while two or three dimensional codes are more appropriate for simulating density currents and detailed lateral movement of sediments, such as during local pressure flushing near reservoir outlets. We conclude that existing codes can successfully simulate sediment management, but because each code has limitations, they require seasoned judgment in their choice, application, and interpretation. Incorporating sediment prediction and management correctly into the planning, design, and operational phases of dam projects is essential for ensuring that the benefits of reservoir storage are sustained over the long term. The implications of our key findings are that sediment management strategies can be successfully simulated and that such simulations should be performed for our aging dams and newly proposed projects.

Water storage reservoirs can be either sustainable or exhaustible. In the absence of sediment management, reservoir storage is an exhaustible resource with long-term consequences. Previous economic planning of reservoirs essentially guaranteed non-sustainable solutions. This paper describes a new economic paradigm for economic assessments of new and existing reservoirs. The new economic paradigm provides a framework for comprehensive accounting of economic benefits and costs over a sufficiently long period of analysis, including cost estimates for dam decommissioning and lost benefits where sediments are not sustainably managed. A case study applies this framework to a hypothetical western US reservoir to quantitatively compare the status quo (i.e., no sediment management) with a selection of sediment management alternatives. Results indicate that sustainable sediment management can be less expensive than the consequences of ignoring sedimentation (e.g., eventual dam decommissioning and replacing lost storage capacity). Additional work shows that beginning sediment management within a decade of reservoir construction prevents the most severe impacts of sedimentation. An investigation of alternative discounting approaches indicates that the approach employed can have a significant impact on economic results.