How many potential wild and scenic rivers are there?

Through the various federal agencies’ land management planning processes and initiatives by the public, a significant number of rivers have been identified for study as potential additions to the National Wild & Scenic Rivers System. For example, the Nationwide Rivers Inventory (NRI), maintained by the National Park Service, has identified over 3,400 river segments as potential candidates for study and/or inclusion into the National System.

Source
Interagency Wild & Scenic Rivers Council