|
the film forum library tutorial contact |
|
With Air, Water Temps in Lower Snake Heating Up,
by Staff
|
Dworshak reservoir will remain within the top 5 ft of full pool through the 4th of July holiday weekend
The reservoir behind central Idaho's Dworshak Dam is full (1,600-foot elevation), air temperatures in the lower Snake River basin are warming into the 100's over the July 4 weekend and beyond, and tailwater temperature at Lower Granite Dam is warming towards 68 degrees Fahrenheit, the maximum allowed by NOAA Fisheries' biological opinion on impacts of the federal hydroelectric system on salmon and steelhead.
All are ingredients that call for the U.S. Army Corps of Engineers this time of year to begin releasing the Dworshak reservoir's cool water to aid migrating juvenile and adult salmon and steelhead downstream in the lower Snake River. Dworshak is on the North Fork Clearwater River.
In a Corps press release Monday, the Corps said it will gradually increase releases from the dam from 3,600 cubic feet per second to 5,300 cfs Monday, July 1, to 7,600 cfs yesterday, July 2, to full powerhouse level of 9,500 cfs tonight, July 3. Releases are expected to remain constant at 9,500 cfs through Friday, July 5, but will continually be monitored and adjusted daily throughout the summer to meet the temperature requirement in Lower Granite Dam's tailwater, the Corps said.
The Corps added that 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."
The flow augmentation was delayed nearly a week this year because cloud cover and cooler air temperatures in the lower Snake River last week kept water temperatures lower, Willow Walker of the Corps' Walla Walla District said at last week's interagency Technical Management Team meeting, June 26, That, she said, could save some of Dworshak's cooler water for when it is needed more this summer.
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, two of the Corps' temperature measuring stations, are at about 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," the Corps said.
Currently at near full pool of 1,600 feet, releases from Dworshak will steadily drop the elevation of the reservoir. The reservoir will remain within the top 5 ft of full pool through the 4th of July holiday weekend, then continue drafting throughout the remainder of summer, the Corps said.
Walker said at this week's TMT meeting, July 3, that it's nice for recreational reasons to have the pool in the top two feet for the 4th of July weekend, although with the flow augmentation, it may be closer to the top four to five feet.
Even at the full powerhouse flow, the Corps expects that total dissolved gas will remain below 110 percent. The agency "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," it said.
Walker said the weather outlook is for high temperatures with over 100-degree highs for the next ten days. With the weather outlook, the Corps is forecasting Lower Granite tailwater temperatures to reach 68 degrees by July 11 and if it keeps going up, it will likely increase outflow at Dworshak Dam by spilling water.
"Monday or Tuesday (next week), we may need to begin spilling," Walker said.
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.
Each summer the Corps steps up the amount of cold water it releases from the Dworshak Reservoir to cool the water for fish passing Lower Granite Dam. The cold water released from the dam takes up to four days traveling through the mainstem of the Clearwater River and into the Snake River to reach Lower Granite Dam.
Inflow into the Dworshak reservoir this week is falling off because most of the snowpack is melted, Walker said last week. Water supply in the Dworshak basin this year ranks as some of the lowest on record.
In fact, the June water supply forecast in the northern portion of the Snake River basin at Dworshak Dam dropped to 1,734 KAF, just 66 percent of average (April through September), and down from 68 percent of average in May (at the time the ninth lowest on record) and 76 percent of average in April.
The June water supply at Lower Granite Dam is 19,076 KAF (April through September), 86 percent of average. It was 88 percent of average in May and 89 percent of average in April.
"Idaho has good water supply conditions except in the north where it's hard not to anticipate issues arising this summer from the low snowpack and low total water year precipitation conditions," said Erin Whorton, Water Supply Specialist for the Natural Resources Conservation Service in Idaho.
"Streamflow forecasts for June through the end of July mimic the same patterns observed with our winter snowpack and total water year precipitation," Whorton noted. "Above normal streamflow is expected in southern Idaho and well below normal streamflow is expected in central and northern Idaho. Near to below normal streamflow is expected in the Wood and Lost basins. This same pattern of below normal streamflow in eastern and northern Idaho was seen in observed runoff during May.
TMT will meet again next week, July 10. Dworshak and temperature augmentation are on the agenda.
TMT is an inter-agency group that consists of sovereign representatives from: the tribes of Nez Perce, Kootenai, Colville, Umatilla, Spokane, and Warm Springs; the states of Oregon, Washington, Idaho, and Montana; NOAA Fisheries; US Fish and Wildlife Service; and the federal Action Agencies – the Bureau of Reclamation, the Corps and the Bonneville Power Administration. TMT responsibilities generally function to address changing conditions, such as water supply, fish migration, water quality, new information, and maintenance issues as it pertains to dam operations in an effort to meet the expectations of applicable biological opinions.
TMT's goal is to protect fish by recommending beneficial operations, including spill, temperature, and flows for ESA-listed salmon, steelhead, sturgeon, and bull trout species within the Columbia River Basin, according to a statement by the Corps. While the TMT encourages conversation, Action Agencies are responsible for management and operation of the Columbia River System. The TMT members can make a recommendation for fish and wildlife benefits to the Action Agencies for their consideration, but the Action Agencies cannot accommodate all requests.
Dam, stream and weather information used at this week's TMT meeting can be found here.
Related Pages:
Dworshak Dam Increases Discharge to Cool River Temperatures by Staff, Big Country News, 7/6/22
Dworshak Reservoir Starts Water Release Early by Staff, Lewiston Tribune, 6/24/21
Cold Water Released from North Idaho Dam to Help Salmon by Associated Press, The Olympian, 6/25/21
Dworshak Flows Increase; Clearwater Level Expected to Rise by Staff, Lewiston Tribune, 5/23/19
Agency Plans to Cut Dworshak Reservoir Water Flows Today by Staff, Lewiston Tribune, 4/6/19
Clearwater River Level to Drop a Foot Below Dworshak; Dam Outflows Reduced for Juvenile Fish by Staff, Daily Fly, 7/19/18
Corps Reduces Dworshak Flows for Fish by Eric Barker, Lewiston Tribune, 3/27/18
Dworshak Dam Tests May Cause River Flow Changes by Staff, Lewiston Tribune, 6/28/18
Rehab of Dworshak's Unit 3 Has its Share of Hiccups by Elizabeth Morgan, Clearwater Tribune, 8/16/17
Dworshak Dam Discharge Flows Lowered to Reduce Flooding Impacts Downstream by Mia Carlson, Daily Fly, 3/20/17
Dworshak Reservoir Filling Up Early by Associated Press, KTVB, 4/26/15
learn more on topics covered in the film
see the video
read the script
learn the songs
discussion forum
