AHSAHKA, Idaho – Recent extremely hot weather conditions and more of the same forecasted for the rest of the week have prompted changes in flow operations at Dworshak Dam and Reservoir near Orofino, Idaho.
Water previously discharging at 5,400 cubic feet per second (c.f.s.) from Dworshak Dam was increased on Saturday to 7,400 c.f.s., again on Sunday to 9,500 c.f.s. and on Monday, July 1, to 13,500 c.f.s., according to U.S. Army Corps of Engineers water-management officials.
Downstream of the dam, water elevation will likely result in Clearwater River elevation increasing by about 1.5 feet at the North Fork confluence.
Based on reservoir modeling, these releases will result in the reservoir lowering by about 5 feet from full-pool (1,600 feet in elevation) by July 4 and about 9 feet down by July 8.
The Columbia River System Biological Opinion mandates the National Oceanic and Atmospheric Administration (NOAA) and the Corps meet several objectives to enhance ESA-listed fish survival, including maintaining minimum water flows for resident fish and salmon and releasing Dworshak Reservoir water to maintain lower Snake River water temperatures and help speed juvenile fish downriver to the ocean
“It takes about four days for releases from Dworshak to reach the downstream side of Lower Granite Dam, where the target temperature gauges are located, so we have to plan well ahead and make adjustments that will be effective at the time we’ll need them further down the river,” said Steve Hall, Walla Walla District Corps reservoir manager. “We are required to maintain water temperatures at Lower Granite below 68 degrees, if possible, using available reservoir-system management methods.”
At noon today, Clearwater River temperature at Orofino, Idaho, was 71 degrees, and Snake River temperature at Anatone, Wash., was 70 degrees, said Hall.
“With such extremely hot weather forecasted to continue through the week, water temperature at Lower Granite is likely to exceed 68 degrees if not regulated, creating conditions in the reservoir system that are unhealthy for ESA-listed fish,” Hall said. “Dworshak’s 43-degree outflows make a big difference in water temperature there and further down the Snake River.”
Corps officials advise boaters and other persons using waterways both in Dworshak Reservoir and below the dam on the Clearwater River 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 -- 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.
Although gradually lowering, Dworshak Reservoir will be within a few feet of full-pool during the holiday weekend. Rangers encourage visitors to enjoy the reservoir safely this weekend, by taking the following precautions:
• When boating on the reservoir, please use caution because lake levels can change quickly – anchor your boat in water deep enough to avoid beaching and leave enough slack in your anchorline to avoid sinking should lake levels fluctuate up or down.
• Changing weather conditions can create unsafe situations on open water. Know the weather and have a float plan.
• Ensure properly fitting, accessible and serviceable life vests are available for each occupant on your boat. Better yet, wear them.
• Keep life jackets on children while on or around the water. Don’t let small children out of your sight.
• Check the serviceability of your boat.
• Before proceeding at higher speeds, familiarize yourself with the area you will be boating as there may be floating woody debris or rocks, stumps and shallow areas not visible from the surface.
• Water temperatures from outflows at Dworshak Dam are about 43 degrees -- be aware of hypothermia risk when wading or swimming in the North Fork and near the confluence of the Clearwater River.
The Dworshak Dam Visitor Center is open daily from 8:30 a.m. to 4:30 p.m. For more information about the movies, water safety, fall recreation opportunities and current conditions, call the visitor center at 208-476-1255.
For more information about reservoir management, please call the Public Affairs Office at 509-527-7020.
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