Who is responsible to administer a river included in the National Wild & Scenic Rivers System?

Rivers included in the National Wild & Scenic Rivers System by act of Congress (under Section 3(a) of the Wild & Scenic Rivers Act) are administered by one of four federal agencies: Bureau of Land Management (BLM), National Park Service (NPS), U.S. Forest Service (USFS), and/or U.S. Fish & Wildlife Service (FWS) as specified in the legislation. Rivers included in the National Wild & Scenic Rivers System at the request of a governor and designated by the Secretary of the Interior (under Section 2(a)(ii) of the Wild & Scenic Rivers Act) are administered by the respective state(s).

Rivers that flow entirely or largely through non-federal lands require an enduring partnership with state and local government to protect values. This collaborative approach is well-evidenced on several “Partnership” rivers administered by the NPS. On these rivers, NPS staff help communities manage their river-related resources locally by bringing together state, county, and community representatives to preserve the Outstandingly remarkable values for which the rivers were designated. This is community-based conservation provides the framework to ensure these rivers will be protected into the future.

Source
Interagency Wild & Scenic Rivers Council