The U.S. Department of Energy was directed by Section 9505 of the SECURE Water Act of 2009 (Public Law 111-11) to submit a report to Congress on each effect of, and risk resulting from, global climate change with respect to: (1) water supplies used for hydroelectric power generation; and (2) power supplies marketed by each Federal Power Marketing Administration. To evaluate the potential effects on the 132 federal hydropower plants in the United States, ORNL designed a spatially consistent assessment approach to enable interregional comparisons. This approach uses a series of hyper-resolution meteorologic, hydrologic, and hydropower models to produce the most up-to-date understanding of long-term hydro-meteorological trends on future hydroelectric generation from federal facilities.