By Jim Stanford on September 13, 2012
The U.S. Bureau of Reclamation will reduce flows out of Jackson Lake Dam into the Snake River a week early, starting Sept. 24.
Water managers will make cuts incrementally, lowering the release from 2,100 cubic feet per second to 300 cfs by Sept. 29. Usually, the bureau begins cutting back water Oct. 1.
The change was not entirely unexpected, given the drought across the West and the bureau’s overarching goal of storing as much water as possible in the Jackson Lake reservoir, to safeguard against continued drought next season.
Scenic rafting operators likely will end their season a little earlier than planned. In 2011, after the third-highest runoff in the last 100 years, there was enough water in the Snake, even as releases were reduced, for rafting companies to run trips through the first week of October.
The bureau set the release schedule after consulting the Wyoming Game and Fish Department. The cutback is gradual so as not to strand fish in side channels and pools. Also, gradual change allows the river to channelize and causes less ecological damage than a sudden drop.
At first, the release will drop by 160 cfs three times a day. By Sept. 29, the cuts will taper to 50 and 40 cfs.
The winter flow of 300 cfs is comparable to what the river volume would be if there was no dam.
Update: The bureau’s operations manager in Burley, Idaho, Mike Beus, said the agency needed to keep more water upstream to have a healthier winter flow in the Snake River. 300 cfs is better than 280, he said. Also, the bureau drew down American Falls and Palisades reservoirs lower than projected because of the hot summer, Beus said. Farmers in Idaho are still irrigating.
(Graph via Wyoming Game and Fish Department)