Lake Nighthorse Test Releases

In May the U.S. Bureau of Reclamation (BOR) conducted three weeks of test releases at Lake Nighthorse. Test releases accomplish two objectives, first-fill engineer Tyler Artichoker said. “If you build something, you test it to see how it functions, but the tests also will show us how the system works when a project sponsor downstream requests water.” Test releases will establish how long it takes for water to reach the Animas River. The information will indicate to project partners in New Mexico how much lead time is required when they call for water.
In addition, test releases, ranging from 5 to 200 cubic feet per second, will show how well drop structures--structures that slow the flow of water and dissipate its energy--work. The structures in effect eliminate 200 feet of the 400-foot drop in elevation from the dam to the river. There are 11 drop structures in Basin Creek from the dam outlet to its confluence with the Animas River five miles away. The lower stretch of Basin Creek was left in its natural state except for the drop structures, constructed of earth fill protected by grouted rip-rap. The upper stretch of Basin Creek was shaped by engineers.
In an interview with Dr. Lisa Fotherby, designer of the stream system, and Barry Longwell, Director of the Four Corners Construction Office, both with the BOR, Basin Creek is intended to deliver the same sediment load to the Animas River despite more flow from Lake Nighthorse, thereby helping to protect fisheries. In essence, the system was designed to act as much like a natural stream as possible. Asked how the drop structures were working, “expectations were exceeded,” stated Fotherby. Future testing will be ongoing.