Officials say sediment problems have put the Niobrara River on a list of the nation's most endangered rivers.
The American Rivers conservation group announced Wednesday that the nearly 570-mile-long river was 10th on the 2013 list. The Colorado River led the list.
The Niobrara begins in Wyoming and flows through northern Nebraska. It joins the Missouri River near the top of Lewis and Clark Lake, the reservoir formed by Gavins Point Dam near Yankton, S.D.
American Rivers says the Missouri River sediment backs up in Lewis and Clark Lake.
The U.S. Army Corps of Engineers is working on sediment and high-water conditions that could affect the village of Niobrara and nearby farm fields.