DURANGO Two years to the day that the U.S. Bureau of Reclamation began filling Lake Nighthorse, the agency Wednesday started testing the effect of releasing water from the reservoir.
Specially made 500-micron tubular nylon nets, fine enough to strain out plankton, ensure that no fish or eggs can escape from the lake.
Last year, the Fish and Wildlife Service stocked 50,000 rainbow trout in the reservoir. Two weeks ago, the Colorado Division of Wildlife added 70,000 kokanee salmon fingerlings to the mix.
The lake is off-limits until the project ends and a recreation master plan and someone to oversee it is in place.
Test releases of water, which will occur for about three weeks, accomplish two objectives, first-fill engineer Tyler Artichoker said.
If you build something, you test it to see how it functions, Artichoker said. But the tests also will show us how the system works when a project sponsor downstream requests water.
Lake Nighthorse is a component of the Animas-La Plata Project, which will provide water for three Native American tribes in Colorado and New Mexico and nontribal entities.
Some A-LP partners will draw water from the reservoir. But two water agencies and the Navajo Nation in New Mexico will get water released from Lake Nighthorse to the Animas River.
The Animas joins the San Juan River near Farmington.
Test releases, ranging from 5 to 200 cubic feet per second, will show how well drop structures basins that slow the flow of water and dissipate its energy work.
The basins in effect eliminate 200 feet of the 500-foot drop in elevation from the dam to the river, Artichoker said.
There are 11 drop structures in Basin Creek from the dam outlet works 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, built of grout-covered rip-rap.
The upper stretch of Basin Creek was shaped by engineers.
Test releases will establish how long it takes for water to reach the Animas, Artichoker said.
The information will indicate to project partners in New Mexico how much lead time is required when they want water.
A maximum of 5,000 acre feet of water will be released during testing, Artichoker said.
Lake Nighthorse, with a capacity of 120,000 acre-feet, is 82 percent full. Its expected to reach capacity in late summer or early fall.