Ahsahka, Idaho —Due to increased temperatures, Dworshak Dam will be increasing their releases to support flow augmentation intended to keep the tailwater of Lower Granite Lock and Dam at or below 68 F.
Dworshak Dam releases will increase from 7,000 cubic feet per second (cfs) on Friday, July 8, to 9,500 cfs by Saturday evening. The river will rise approximately 6 inches during the flow changes each evening.
The specific target of flow augmentation is to keep the tailwater of Lower Granite at or below 68 F. Currently, Lower Granite’s tailwater is approximately 63 F, and the natural river temperatures in the Clearwater River at Orofino and in the Snake River at Anatone are approximately 62 F and 65 F respectively.
With temperatures in the region being forecast to hit high 90s in the next 10 days and possibly nearing the low 100s, the natural river temperatures will begin to increase. Releases of cooling water from Dworshak are necessary to help offset the natural river temperatures and to minimize impacts as flow augmentation begins.
Forebay elevations in Dworshak Reservoir will change due to the increased releases needed for flow augmentation. The reservoir elevation as of July 6, is approximately 1,599.75 feet. The reservoir elevation will begin a steady decrease Friday night leading to a tentative elevation near 1,590 feet between July 20 and July 24. For the remainder of the summer, outflows from Dworshak will vary to meet the needs of temperature flow augmentation at Lower Granite, with the reservoir lowering by approximately 80 feet to an elevation of 1,520 feet by September 30.
The rate of change in downstream river stage limit of one foot per hour, as measured at the United States Geological Survey (USGS) Clearwater River Near Peck, ID (gage #13341050), will not be violated due to project operations.
For safety, the public is advised to be aware of the danger associated with fluctuating river flows and elevations. The river at this time of year is deep, cold, and fast, so extreme caution should be used near riverbanks. 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 Dworshak water-management conditions can be viewed on the Walla Walla District website at https://www.nwd.usace.army.mil/CRWM/Water-Control-Data/Project-Data/.