What are the responsibilities of the federal wild and scenic river-administering agency (for rivers designated by Congress)?

The federal wild and scenic river-administering agency is responsible for implementing the Wild & Scenic Rivers Act’s requirements, including the development of a comprehensive management plan for each river within three full fiscal years from the date of designation. It is also responsible to protect and enhance a river’s values, through its authorities on federal lands and through voluntary, cooperative strategies developed with other governments, tribal nations, and landowners on non-federal lands, and to evaluate water resources projects under Section 7(a).

Source
Interagency Wild & Scenic Rivers Council