What is the role of a state in managing a river designated under Section 2(a)(ii)?

The Wild & Scenic Rivers Act states that rivers designated under Section 2(a)(ii) “shall be administered by the State or political subdivision thereof without expense to the United States other than for administration and management of federally owned lands.” The state is responsible for providing protection, except on federally administered lands and with respect to Section 7(a) determinations and securing a federal reserved water right under Section 13(c), both of which are made by a federal agency. The National Park Service provides ongoing technical assistance and partnership efforts with local managers and stakeholders on many of these rivers.

Source
Interagency Wild & Scenic Rivers Council