The US Department of Energy (DOE) was directed by Section 9505 of the Secure Water Act of 2009 (Public Law 111-11) to submit a report to congress on the effects of climate change on federal hydropower systems. The "9505 assessment" examines climate change effects on water available for hydropower operations and the future power supplies marketed from federal hydropower projects. It is the result of extensive consultation with the federal Power Marketing Administrations (PMAs), as well as with other federal agencies including federal hydropower owners (the US Army Corps of Engineers and the Bureau of Reclamation). Federal hydropower comprises approximately half of the US hydropower portfolio. In addition to evaluating effects and risks from climate change, the assessment addresses potential changes in operation or contracting practices that could mitigate adverse impacts. Potential adaptation strategies are also identified. The 9505 assessment will promote a better understanding of the sensitivity of federal power plants to water availability, and it provides a basis for planning future actions that will enable adaptation to climate variability and change. The end-users of this information are Congressional members and their staff, PMAs and their customers, federal hydropower owners and operators, and the DOE Water Power Program.