As called for in the March 24, 2010, Memorandum of Understanding (MOU) for Hydropower, the U.S. Department of Energy (DOE), the U.S. Department of the Interior (DOI), the U.S. Army Corps of Engineers (USACE), environmental stakeholders, and the hydropower industry are collaborating to identify opportunities to simultaneously increase electricity generation and improve environmental services in river basins of the United States. New analytical tools provide an improved ability to understand, model, and visualize environmental and hydropower systems. Efficiencies and opportunities that might not be apparent in site-by-site analyses can be revealed through assessments at the river-basin scale. Information from basin-scale assessments could lead to better coordination of existing hydropower projects, or to inform siting decisions (e.g., balancing the removal of some dams with the construction of others), in order to meet renewable energy production and environmental goals. Basin-scale opportunity assessments would inform energy and environmental planning and address the cumulative effects of hydropower development and operations on river basin environmental quality in a way that quantifies energy-environment tradeoffs. Opportunity assessments would create information products, develop scenarios, and identify specific actions that agencies, developers, and stakeholders can take to locate new sustainable hydropower projects, increase the efficiency and environmental performance ofmore » existing projects, and restore and protect environmental quality in our nation's river basins. Government agencies and non-governmental organizations (NGO) have done significant work to understand and assess opportunities for both hydropower and environmental protection at the basin scale. Some initiatives have been successful, others less so, and there is a need to better understand the legacy of work on which this current project can build. This background literature review is intended to promote that understanding. The literature review begins with a discussion in Section 2.0 of the Federal regulatory processes and mission areas pertaining to hydropower siting and licensing at the basin scale. This discussion of regulatory processes and mission areas sets the context for the next topic in Section 3.0, past and ongoing basin-scale hydropower planning and assessment activities. The final sections of the literature review provide some conclusions about past and ongoing basin-scale activities and their relevance to the current basin-scale opportunity assessment (Section 4.0), and a bibliography of existing planning and assessment documents (Section 5.0).« less