The U.S. Department of Energy is currently preparing an assessment of the effects of climate change on federal hydropower, as directed by Congress in Section 9505 of the Secure Water Act of 2009 (P.L. 111-11). This paper describes the assessment approach being used in a Report to Congress currently being prepared by Oak Ridge National Laboratory. The “9505 assessment” will examine climate change effects on water available for hydropower operations and the future power supplies marketed from federal hydropower projects. It will also include recommendations from the Power Marketing Administrations (PMAs) on potential changes in operation or contracting practices that could address these effects and risks of climate change. Potential adaption and mitigation strategies will also be identified. Federal hydropower comprises approximately half of the U.S. hydropower portfolio. The results from the 9505 assessment will promote better understanding among federal dam owners/operators of the sensitivity of their facilities to water availability, and it will provide a basis for planning future actions that will enable adaptation to climate variability and change. The end-users of information are Congressional members, their staff, the PMAs and their customers, federal dam owners/operators, and the DOE Water Power Program.