A synthesis of environmental and recreational mitigation requirements at hydropower projects in the United States

Environmental mitigation plays an important role in the environmentally sustainable development of hydropower resources. However, comprehensive data on mitigation required by the Federal Energy Regulatory Commission (FERC) at United States (US) hydropower projects is lacking. Therefore, our objective was to create a comprehensive database of mitigation required at non-federal hydropower projects and provide a synthesis of available mitigation data. Mitigation data was collated for over 300 plants licensed or relicensed from 1998 through 2013. We observed that the majority of FERC mitigation requirements deal with either hydrologic flows or recreation and that hydropower plants in the Pacific Northwest had the highest number of requirements. Our data indicate opportunities exist to further explore hydropower mitigation in the areas of environmental flows, fish passage, and water quality. Connecting these data with ecological outcomes, actual flow data, and larger landscape level information will be necessary to evaluate the effectiveness of mitigation and ultimately inform regulators, managers, and planners.