The Secretary is authorized, in conjunction with any reservoir heretofore constructed by him pursuant to the Federal reclamation laws or any reservoir which is otherwise under his control, except reservoirs within national wildlife refuges, to investigate, plan, construct, operate and maintain, or otherwise provide for public outdoor recreation and fish and wildlife enhancement facilities, to acquire or otherwise make available such adjacent lands or interests therein as are necessary for public outdoor recreation or fish and wildlife use, and to provide for public use and enjoyment of project lands, facilities, and water areas in a manner coordinated with the other project purposes. Lands, facilities and project modifications for the purposes of this subsection may be provided only after an agreement in accordance with subsection (b) or (c) of section
460l–14 of this title has been executed.