Since the U.S. Department of the Army (through the U.S. Army Corps of Engineers), U.S. Department of Energy (through the Office of Energy Efficiency and Renewable Energy), and U.S. Department of the Interior (through the Bureau of Reclamation) signed their Memorandum of Understanding (MOU) for Hydropower in 2010, these agencies have endeavored to advance their mutual goals for greater development and utilization of clean, reliable, cost-effective, and sustainable hydropower generation in the U.S. This Action Plan renews the commitments of the three agencies to the 2010 MOU and details the second phase of collaboration, which seeks to support the Administration's goals for doubling renewable energy generation by 2020 and improving federal permitting processes for clean energy as established in the President's Climate Action Plan. Through continued collaboration and partnerships with other federal agencies, the hydropower industry, the research community, and numerous stakeholders, these agencies intend to continue working toward the objectives and goals of the MOU.The MOU agencies have complementary and overlapping roles in the domain of hydropower research, planning, development, and operations. This Action Plan provides a structure for collaborative activities that clarifies those roles and enhances the efficiency and benefits of coordinated activities in the following areas: (a) Technology Development, (b) Asset Management, (c) Hydropower Sustainability, (d) Quantifying Hydropower Capabilities and Value in Power Systems, and (e) Information Sharing, Coordination, and Strategic Planning. The sections that follow describe the roles of the MOU agencies in each of these areas and the specific action items on which the MOU agencies plan to collaborate to accomplish their goals.