Should federal agencies also consider the eligibility of other potential rivers not included in the Nationwide Rivers Inventory?

Yes.  The federal agency should consider a wide variety of internal and external sources from which to identify potentially eligible rivers.  These sources may include:  American Rivers’ “Outstanding Rivers List,” statewide river inventories/assessments, published guidebooks, etc.  The important point is to develop and apply standardized criteria through a documented evaluation process for potential wild and scenic rivers.

Source
Interagency Wild & Scenic Rivers Council