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Snake flows headed downward

October 2, 2017 GMT

The past historic winter bolstered water tables and, in turn, stream and river levels throughout late summer and into early fall.

But Snake River levels will soon be headed downward for a reason that’s out of Mother Nature’s control. The Bureau of Reclamation is tapering off the flow of water spewing out of Jackson Lake Dam starting today to store water in the Snake’s furthest upstream impoundment.

Releases out of the dam have for weeks been around 2,200 cubic feet per second, but they will be notched down throughout the week until they reach 400 cfs Friday.

The transition to the winter rate of flow usually comes a few days earlier in the year. It was pushed back by about a week this year because of recent rain.

Flows of 400 cfs out of the dam will likely be maintained all winter, meaning swift floats on the Snake south of Jackson Lake are done for the year.

Also further downstream, such as at South Park, flows are about to cut significantly. The gauge at Swinging Bridge read nearly 4,500 cfs Sunday — 50 percent more than the average — but by week’s end it will likely read less than 3,000 cfs.

Jackson Lake is currently 77 percent full and will begin to slowly fill once the winter dam discharge rate is achieved. Inflow from the Snake River north of the lake was over 550 cfs, and that’s not counting other Jackson Lake tributaries that aren’t monitored.

Palisades Reservoir, 88 percent full, was discharging about 4,500 cfs into the South Fork of the Snake River. Releases at Palisades Dam are scheduled to be cut to 3,500 cfs or less on Oct. 10 to accommodate upkeep of the dam. The work will continue through the first few weeks of November.