AHSAHKA, Idaho -- Dworshak Dam releases will increase from 3,600 cubic feet per second (cfs) on Monday July 1 to the maximum powerhouse capacity of 9,500 cfs by the evening of Wednesday July 3 for the start of flow augmentation.
Between the hours of 7 p.m. and 11 p.m. on Monday, July 1 releases will increase from 3,600 cfs to 5,300 cfs. Between the hours of 7 p.m. and 11 p.m. on Tuesday, July 2 releases will increase from 5,300 cfs to 7,600. Between the hours of 7 p.m. and 11 p.m. on Wednesday, July 3rd releases will increase from 7,600 cfs to 9,500 cfs.
Releases are expected to remain constant at 9,500 cfs through Friday, July 5. Releases will be monitored and adjusted daily to meet downstream temperature requirements as needed throughout the remainder of summer. The rate of change in downstream river stage will remain below 1 foot per hour as measured at the United States Geological Survey (USGS) Clearwater River Near Peck, ID (gage #13341050). The total increase in river elevation at this gage from July 1 through 3 will be approximately 1.5 feet.
As river temperatures increase in the summer months, cooling water from Dworshak Reservoir is released to increase fish survival by moderating river temperatures and flows in the Snake River. Operations to provide cooling water are referred to as flow augmentation. The specific target of flow augmentation is to keep the tailwater of Lower Granite Lock and Dam at or below 68° F. Currently, Lower Granite’s tailwater is approximately 66° F, and the natural river temperatures upstream of Lower Granite in the Clearwater River at Orofino and in the Snake River at Anatone are approximately 62° F and 66° F respectively. Flow augmentation is beginning this week because natural river temperatures are nearing 68° F and hot regional temperatures are expected over the Fourth of July weekend.
Dworshak Reservoir is currently at its full pool of 1,600 feet. As releases increase for flow augmentation, the reservoir elevation will begin a steady draft. The reservoir will remain approximately within the top 5 ft of full pool through the Fourth of July holiday weekend, then continue drafting throughout the remainder of summer.
The current operation will result in total dissolved gas (TDG) remaining below 110%. USACE will continue to work with regional water managers, other agencies, tribes, and fish managers and hatcheries in joint efforts to meet reservoir objectives and keep TDG below the Idaho State maximum threshold of 110%, when possible.
For safety, the public is advised to be aware of the danger associated with fluctuating river flows and elevations. 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/.