Lake Nighthorse is a reservoir created by the 270 feet (82 m) high Ridges Basin Dam southwest of Durango in La Plata County Colorado. As part of the Animas-La Plata Water Project, Lake Nighthorse provides water storage for tribal and water right claim-holders along the Animas River.
The Bureau of Reclamation began construction in 2003, with the reservoir filling to capacity on June 29, 2011 at a total cost of $500 million. Lake Nighthorse is named in honor of former United States Senator Ben Nighthorse Campbell, R-Colo.
The lake is open as of April 1, 2018 for recreation, fishing and boating. It has been stocked with kokanee salmon, rainbow trout and brown trout.