Snake River flows

After a long and drawn-out runoff season, the Snake River is flowing near it's historical median rate of flow. 

River and stream levels all around Jackson Hole are on their way down as runoff abates, and water managers have fixed the flows coming out of Jackson Lake for the balance of summer.

High flows were blunted this year, and cooler temperatures also prolonged the runoff by keeping upper-elevation snow in place, said Brian Stevens, a Snake River water operations manager for the Bureau of Reclamation.

“Cold temperatures really dampened peak flow this year, but there was some good runoff,” Stevens said. “It was strong.”

River levels topped out in the Snake River Canyon at 18,000 cubic feet per second, a crest achieved in the middle of May and then again twice in the first half of June. The historical average high mark is 15,000 cfs, which typically comes the first week of June.

Although easily clearing the average, 2019’s peak flows fell well short of the two preceding banner water years of 2017 (over 30,000 cfs in the canyon) and 2018 (25,000 cfs).

The third consecutive wetter-than-average water year has both Jackson Lake and Palisades Reservoir totally full again. Releases out of Jackson Lake reached their summer rate of 2,330 cfs early this week, Stevens said. A slow drawdown should bring Jackson Lake to 68% of its water storage capacity by the time winter is approaching.

Usually, federal water managers target leaving the augmented lake 76% full, but routine maintenance at Jackson Lake Dam demands that it drop down further this year.

“But that water will be stored in Palisades,” Stevens said, “so it won’t be going too far away.”

Palisades, which is also full, is currently discharging just over 13,000 cfs. Early-summer flushing flows that were intended to put the hurt on spawning nonnative rainbow trout were called off this year.

“The Henry’s Fork Foundation did some work for Idaho Fish and Game,” Stevens said, “and found that the flushing flows weren’t producing the results they thought they were going to get.”

South Fork anglers say the fishing was better this June as a result of the stable water.Heading into the heart of summer, the Snake River is running at 8,400 cfs and was carrying almost exactly as much water as it historically has during the second week of July. Other streams large and small are also running near or slightly above their long-term medians, such as the Buffalo Fork (1,300 cfs), Gros Ventre River (1,100 cfs) and Flat Creek (200 cfs).

One upside of the lower, slower flows is that the bite has picked up for anglers after the cold May and June that kept the water silted and fast.

“Everything’s ramping up,” Westbank Anglers shop clerk Paul Angiolillo said, “and it’s been getting buggy for the last few weeks.”

“The Snake is still just a little off color, but it’s fishing,” he said. “We’ve been fishing dry flies for the last week and a half, or two.”

Contact Mike Koshmrl at 732-7067 or env@jhnewsandguide.com.

Mike has reported on the Greater Yellowstone Ecosystem's wildlife, wildlands and the agencies that manage them for 7 years. A native Minnesotan, he arrived in the West to study environmental journalism at the University of Colorado.

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