AHSAHKA, Idaho – Discharge flows from Dworshak Dam will be decreased starting at 10 a.m. on Friday, April 18, from approximately 20,000 c.f.s. (cubic feet per second) to about 11,000 c.f.s. to balance flood control operations and flows to support spring smolt outmigration, according to U.S. Army Corps of Engineers water-management officials. The decrease to 11,000 c.f.s. should be completed by noon. This discharge rate is planned to last at least through the end of April, but is subject to change.
The Corps advises Clearwater River boaters and other people using regulated waterways to always be alert to changes in water elevation and volume of flow.
Water-management changes can be especially dynamic this time of year as weather systems come through the region and temperatures begin to rise. This has not been a typical year for water management at Dworshak. Precipitation was lower in January followed by very heavy precipitation in February and March. This led to very high inflows. A record inflow of 34,000 c.f.s. occurred on March 10.
Flood control analysis led the Corps to make additional space in the Reservoir for spring runoff. Outflows were increased to 20,000 c.f.s. on March 22 and held at that level. Maximum Clearwater North Fork channel capacity is 25,000 c.f.s.
Friday’s decreased flow means the reservoir will likely not drop below 1,486 feet elevation. The deepest flood-control draft elevation is 1,445 feet elevation. In May and June, flood control is typically balanced with the desire to have Dworshak Reservoir close to full pool (1,600 feet elevation) in time for the July 4 holiday weekend, said Steve Hall, reservoir manager for the Corps’ Walla Walla District.
Managing water levels to reduce flood risk throughout the reservoir system requires constant monitoring of weather and snow-pack, plus making appropriate adjustments to ensure enough storage space is available for rainfall and snowmelt that occurs each spring.
Current water-management conditions can be viewed online at www.nwd-wc.usace.army.mil/nww/rreports.htm -- click on “Hourly” and look in the “TOTAL” column under the “OUTFLOW” heading on the reservoir report. Reservoir elevation is found in the “FOREBAY” column under the “EL AT POWERHOUSE” heading.
During fiscal year 2012, 1.98 billion kW hours of electrical power was produced by Dworshak Dam’s three generating units. Since Dworshak Dam became operational in June 1972, it has prevented more than $2.8 million in potential local flood damages.
For more information, call the Public Affairs Office at 509-527-7020.
NOTE TO EDITORS: Also see attached separate fact sheet “Dworshak Reservoir Operations - Spring and Summer 2014.” It’s available at http://www.nww.usace.army.mil/Portals/28/docs/dworshak/FS_DworshakReservoir140417.pdf.