The United States has produced clean, renewable electricity from hydropower for more than 100 years, but hydropower-producing facilities represent only a fraction of the infrastructure development that has taken place on the nation's waterways. In contrast to the roughly 2,500 dams, the United States has more than 80,000 non-powered dams (NPDs)-- dams that do not produce electricityproviding a variety of services ranging from water supply to inland navigation. Importantly, many of the monetary costs and environmental impacts of dam construction have already been incurred at NPDs, so adding power to the existing dam structure can often be achieved at lower cost, with less risk, and in a shorter time-frame than development requiring new dam construction. This book discusses hydropower generation, government involvement at federal and non-federal levels and the energy potential at non-powered dams.