Dams provide an important opportunity to gain clear insights into the issues involved in incorporating socioeconomic and ecological considerations into decisions about the environment. Socioeconomic and ecological needs for rivers are rarely congruent and dams pose serious risks to humans and ecosystems. Dam removal and environmental mitigation of the impacts of dams are two management options that attempt to balance the socioeconomic and ecological needs for needs.

Dam removal can have a number of positive environmental benefits. A literature review included in Chapter 1 suggested that biotic diversity can increase through restoration of the natural flow regime and preferred spawning grounds. Riffle/pool sequences, gravel, and cobble can reappear. Fish passage can also be improved. Some short-term detrimental impacts of removal can include increased sediment load and supersaturation.

Dam mitigation can also have positive environmental effects, which I examined in Chapter 2. The Tennessee Valley Authority’s Reservoir Releases Improvement (RRI) Program was an attempt to improve minimum flow and dissolved oxygen in their tailwaters while still maintaining socioeconomic services. My results indicated that DO and flow did increase following the RRI program and the biological response appeared to include a shift in the composition of the macroinvertebrate community towards more taxa that prefer higher water quality.

In Chapter 3, I examined the relative importance of ecological and socioeconomic rationales for dam removal. Interviews of state dam safety officials and an examination of Pennsylvania dam removal permits showed that while dam removal is occurring in most states, it is occurring primarily in response to socioeconomic concerns, such as dam deterioration, obsolescence and repair costs. Environmental rationales are playing a role in some states, but usually in a secondary position.

In Chapter 4, I explained that the variation among dams, the tradeoffs of each of the management alternatives and decision-aiding tools make it difficult to make decisions about dams. One of the most promising tools is adaptive ecosystem management, which explicitly addresses ecosystem complexity and stakeholder input. To truly improve the decision-making process for dams, we need to continue to attempt to forge functioning models of how all of the pieces fit together.