Lower Snake Water Tempsby Mike O'Bryant
Cold water outflows from Dworshak Dam could drop to 10,000 cubic feet per second Monday, keeping with the operation proposed by the Nez Perce Tribe and the Idaho Department of Fish and Game.
That operation is intended to extend Dworshak's cold water effects at Lower Granite Dam through mid-September to benefit late migrating juvenile salmon from the Clearwater River and adult salmon and steelhead migrating upstream.
However, the recent spate of extremely hot weather in the Northwest is sending air temperatures in eastern Washington and western Idaho beyond 100 degrees Fahrenheit. That could cause the Technical Management Team, which may meet this afternoon (Aug. 1), to increase flows from Dworshak Dam instead as a way to prevent overheating at Lower Granite Dam.
The Nez Perce/Idaho operation at Dworshak requires flows at the dam that would result in a reservoir elevation of 1,535 feet at the end of July and 1,520 feet by mid-September. The NOAA Fisheries 2000 Biological Opinion calls for using the water available for augmenting flows with the cool water through Aug. 31, and to draft the reservoir to its minimum of 1,520 feet by that date.
TMT agreed last week to try to meet the Nez Perce/Idaho goal as long as water temperatures at Lower Granite Dam stay cool enough that migrating juvenile salmon are not harmed.
NOAA Fisheries' Paul Wagner said there is some divergence of opinion among federal and state salmon managers, but that generally there is some support to stay at the 1,535 foot target unless water at Lower Granite Dam began to heat up. The temperature in the dam's tailwater this week has stayed fairly cool -- 65.2 to 67.1 degrees -- despite the higher air temperatures. Further downstream on the Snake River, temperatures at Little Goose Dam's tailwater reached 68 degrees.
"Twelve thousand seems to be doing the trick," Wagner told TMT at this week's meeting, referring to the 12 kcfs flows currently being released from Dworshak Dam. However, with high temperatures predicted this week at Lewiston, Idaho, he suggested that fisheries managers monitor the water temperature daily and alert the full TMT to any problems today.
Kyle Martin of the Columbia River Inter-Tribal Fish Commission predicted that weather in the area will begin to cool into the low-90s this weekend and that most of the hot weather will then be behind the area.
"Summer weather started about three weeks early this year," Martin said. Within a week, he expects to begin to see a late summer cooling down.
One of the reasons the cold water flows out of Dworshak Dam continues to keep Snake River water cooler is that overall flows in the Snake River are dropping which results in a rise in the ratio of water in the river that is provided by Dworshak Dam, said Cindy Henriksen of the U.S. Army Corps of Engineers. River flow at Lower Granite this week hovered around 32 kcfs. The Corps expects the seasonal average to be about 28 kcfs.
Fisheries managers had proposed holding outflows from Dworshak Dam at 14 kcfs through August, believing it is best to provide augmentation flows earlier, at which time the reservoir would have fallen to an elevation of 1,520 feet. On the other hand, the Nez Perce/Idaho plan called for lower augmentation flows through July and August, thus spreading the benefits of Dworshak's cooler waters later into the year.
In addition to dropping Dworshak flows to 12 kcfs, the Nez Perce/Idaho proposal would drop flows to 11 kcfs Aug. 4, to 10 kcfs Aug. 11, and 8 kcfs Aug. 25, and then it would increase flows slightly to 8.4 kcfs from Sept. 1 to Sept. 15. At that time, flows would drop to 1.4 kcfs as the reservoir reaches an elevation of 1,520 feet. Those flows were adjusted this week by the Corps to 10 kcfs Aug. 4, 9 kcfs Aug. 11 and 7 kcfs Aug. 25 in order to meet the overall goal of reaching a reservoir elevation of 1,535 feet Aug. 31.
Technical Management Team: www.nwd-wc.usace.army.mil/TMT/index.html
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