For purposes of the Niobrara Scenic River Act, Niobrara scenic river corridor means the area designated as a national scenic river and a part of the national wild and scenic rivers system under 16 U.S.C. § 1274(a)(117), as such section existed on May 24, 1991, and described in the 1996 Niobrara National Scenic River General Management Plan/Environmental Impact Statement.