AHSAHKA, Idaho – To increase Dworshak Reservoir capacity to manage expected high inflows, water discharge from Dworshak Dam near Orofino, Idaho, will continue to be increased about 1,000 cubic feet per second (CFS) per day. The increases will be made from 8 p.m to 9 p.m. each night through this weekend, as planned last week by regional water managers. The regional water managers are working to control flows from the reservoir into the North Fork of the Clearwater River to meet seasonal flood-risk-management requirements.
“February precipitation in the North Fork Clearwater River basin was 214 percent of normal,” said Steve Hall, Water Program Manager for the U.S. Army Corps of Engineers Walla Walla District, which operates Dworshak Dam and Reservoir. “We’re anticipating more water inflow at Dworshak in the next 10 days. That’s what is now driving our flood-risk reduction and public safety decisions.”
Dworshak flows are about 17,500 cfs today. Flows will increase 1,000 cfs beginning tonight at 8 p.m. and will continue to be increased 1,000 cfs each night between 8 p.m. and 9 p.m. until flows reach approximately 22,000 cfs by about Monday, March 13. The water surface elevations of the Clearwater River are expected to minimally fluctuate during this current gradual increase in flows up to 22,000 cfs. Additional increases may be necessary as conditions change.
The Corps works with regional water managers, other agencies and tribes, and fish managers and hatcheries as the Corps reduces flood risk. That includes joint efforts to keep total dissolved gasses (TDG) below the Idaho State maximum threshold, when possible. When water is released from the dam, gasses can be absorb into the water. High TDG levels can be unhealthy for fish.
The Corps sent a team to adjust TDG removal equipment at the Dworshak National Fish Hatchery operated for the Corps by the U.S. Fish and Wildlife Service and the Nez Perce Tribe. The Corps team is also measuring TDG in the river and in the hatcheries including monitoring TDG in hatchery raceways.
“The Corps’ highest priority is public safety, so we will operate to provide flood risk reduction benefits,” Hall said. “We’ll continue to monitor river basin conditions, weather forecasts, and impacts on fish. We’ll also continue our efforts working with other agencies to reduce the impact of flood operations on fish.”
Boaters, anglers and other people using waterways both in Dworshak Reservoir and below the dam on the Clearwater River are advised to be alert to changes in water elevation and volume of flow. Current water-management conditions can be viewed on the District website at www.nwd-wc.usace.army.mil/nww/rreports.htm.
Dworshak Powerhouse Unit 3 is out of service from September 2016 through mid-2017 and is unable to pass water from the reservoir until it goes back into service. The 220,000-kilowatt generator is capable of passing 5,600 cfs through the powerhouse. Units 1 and 2 combined pass 4,800 cfs. The dam has three Powerhouse units.
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Release no. 17-022