US Army Corps of Engineers
Walla Walla District

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19-080 Dworshak discharge flows increased to cool rising river temperatures

Published July 5, 2019

Recent 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 5,300 cubic feet per second (cfs) from Dworshak Dam began increasing this afternoon toward target flows of 9,450 cfs, according to U.S. Army Corps of Engineers water-management officials. Downstream of the dam, water elevation will likely result in Clearwater River surface elevation increasing by about 1 foot at the USGS gage located at Peck.

The National Oceanic and Atmospheric Administration’s (NOAA) Columbia River System Biological Opinion (BiOp) requires the Corps to 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.

“We are required to maintain water temperatures at Lower Granite below 68 degrees, if possible, using available reservoir-system management methods,” said Johnathan Roberts, a Walla Walla District reservoir regulator. “It takes about three days for cold-water 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 at Dworshak that will be effective at the time we’ll need them further down the river.”

Today, at noon, Snake River temperature on the downstream side of Lower Granite was 66.7 degrees, said Roberts.

“With hot weather forecasted to continue, water temperature at Lower Granite is likely to soon exceed 68 degrees if not regulated, creating conditions in the reservoir system that are unhealthy for ESA-listed fish,” Roberts said. “Dworshak’s 43-degree outflows make a big difference in water temperature there and further down the Snake River.”

Cold-water releases from Dworshak will be adjusted as needed to keep temperatures below the BiOp threshold, while conserving as much water as possible, Roberts added.

Dworshak Reservoir reached recreation pool elevation (1,598 mean sea level) on June 7, offering earlier-than-usual prime water-recreation conditions, with all boat ramps and campsites accessible for visitors. Park Rangers advise boaters to be aware of potentially hazardous conditions associated with the reservoir being full.

“That means woody debris that is usually beached along the shoreline later during the summer is floating around and can make boating difficult,” explained Colten Shimer, Dworshak natural resource specialist. “Before proceeding at higher speeds, boaters should become familiar with the area and be on the lookout for woody debris or rocks, stumps and shallow areas not visible from the surface.”

Dworshak natural resources staff invite visitors to camp, boat and play at Dworshak Reservoir:

• Bass and kokanee fishing are plentiful.
• Shoreline campsites are open, clean and ready for use.
• Destination and safe-harbor docks have all been cleaned, repaired and/or replaced.
• Dent Campground is open and accepts reservations at www.recreation.gov.
• Dworshak State Park is also open https://parksandrecreation.idaho.gov/parks/dworshak.
• Life jacket loaner-boards are open and fully stocked. Please, use and return them.

Corps officials advise boaters and other people 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.nww.usace.army.mil/Missions/WaterManagement.aspx.

Rangers encourage visitors to enjoy the reservoir safely, 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. 
• 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., offering guided public tours of the dam at 10 a.m. and 1 p.m. The center also offers a variety of interpretive displays and movies about Dworshak and the history of the Clearwater River area, including the popular “Last of the Log Drives.” 

For more information regarding water levels, facilities access or recreation, call the visitor center at (208) 476-1255, check out Dworshak Dam’s Facebook page at www.facebook.com/dworshakdam, or stop by the Visitor Center. Recorded-message water level and recreation information is also available by calling 800-321-3198.

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Contact
Public Affairs Office
509-527-7020
cenww-pa@usace.army.mil

Release no. 19-080