AHSAHKA, Idaho – Dworshak Dam discharge flows will begin decreasing at 12:01 a.m. tomorrow, April 15, according to U.S. Army Corps of Engineers officials.
Flows will decrease during a 4-hour period from the current volume of 25,000 cubic feet per second (cfs) to a target flow of 8,000 cfs. The decrease will result in lower water levels and velocities in the North Fork Clearwater River. The change in flows coming from the Clearwater River’s North Fork will affect river surface elevation at and near the confluence with the main stem Clearwater River as flows are being adjusted.
Reducing Dworshak discharge flows will also lower total dissolved gas (TDG) in the river to levels better tolerated by juvenile fish species.
This change in flow operations is being conducted because low-elevation snowpack is no longer anticipated to increase. Currently, about 2.9 million acre-feet of water remains in the North Fork sub-basin snowpack, and about 1.4 million acre-feet of available space remains of the reservoir’s 2 million acre-feet capacity. Dworshak Reservoir’s surface elevation is currently about 1,505 feet mean sea level. Future seasonal increases or decreases may be necessary as conditions change.
For safety, the public is advised to be aware of danger associated with fluctuating river flows and elevations. Outflow water is deep, cold and fast, so extreme caution should be used near river banks. 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 up or down in water elevation and volume of flow. Current Dworshak water-management conditions can be viewed on the Walla Walla District website at www.nwd-wc.usace.army.mil/nww/rreports.htm.
This year, 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. Water being passed through the Powerhouse units contain less total dissolved gasses than water spilled from higher up the dam. The dam has three Powerhouse units.
Release no. 17-050