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April 10, 2012 7:47 am

Reservoirs holding steady

Written by Gib Mathers

Snow is melting quickly in the Absaroka Mountains, but so far reservoirs in the Big Horn Basin are filling or are expected to do so.

Water storage in the local big three reservoirs — Buffalo Bill, Boysen and Big Horn/Yellowtail — is looking pretty good.

The snow water equivalent in the Shoshone River basin has dipped from 100 percent since mid March, said Lyle Myler, Bureau of Reclamation acting Wyoming area manager in Mills.

Indeed, according to the Monday morning snow report from the Natural Resources Conservation Service, Shoshone River Basin is at 90 percent, down a notch from 91 percent last week. The Big Horn River basin dropped from 96 percent one week ago to 89 percent Monday. But that is comparatively good news. The statewide average is at 63 percent SWE.

Buffalo Bill Reservoir is 71 percent full, at 458,940 acre feet. The 30 year average from 1982 to 2011 for this time of year is 412,000 acre feet. Pool elevation is 5368.8 feet, and pool elevation to fill is 24.8 feet, according to data from the Bureau of Reclamation.

The bureau is anticipating 700,000 acre feet in the next four months during spring runoff.

The Natural Resource Conservation Service is predicting 705,000 acre feet. Even if the Buffalo Bill received 550,000 acre feet, it would still fill.

“I don’t see a problem with us filling the reservoir,” Myler said.

Buffalo Bill has been rising slightly since the end of March. On April 1, Myler increased the release from 400 cubic feet per second to 600 cfs, he said.

From 1916 to 2011, Buffalo Bill has averaged 716,000 acre feet inflow during the four month spring runoff. Even in dry years, the reservoir has adequate water. And, typically, a dry year is followed by a wet year, allowing Buffalo Bill to catch up. For example, in 1976, the reservoir received 309,000 acre feet during the spring runoff. But the following spring, 885,000 acre feet arrived. The Shoshone River basin — the North and South forks of the Shoshone River and its tributaries above Buffalo Bill — usually produces good snowpack, Myler said.

Still, the National Weather Service is predicting continued warm and dry weather above the reservoir. If that is the case, to maintain necessary storage, Myler said he will take actions such as lowering the release below the dam.

“Right now, our expectation is we’ll fill the reservoir and be able to meet deliveries,” Myler said.

Water in Boysen Reservoir is at 636,957 acre feet, and the reservoir is almost 86 percent full. Boysen’s 30-year average for the end of March is 540,300 acre feet. Pool elevation is 4,719.4 feet, and pool elevation to fill is 5.6 feet. Outflow was at 1,055.5 cfs Sunday, according to data from the bureau.

During the four-month spring runoff, Myler is anticipating 550,000 acre feet inflow. That equals 96 percent of the 30-year average, or a little more than 571,000 acre feet.

Water in Big Horn/Yellowtail Reservoir is at 824,913 acre feet. It is almost 81 percent full. Pool elevation is 3619.4 feet and pool elevation to fill is 20.6 feet, according to data from the bureau.

Outflow was at 2815.5 cfs Sunday, but the plan was to increase the discharge. The bureau intended to flush 7,000 cfs until Thursday to restore side channels and fish habitat on the Big Horn River.

“River recreationists are advised to exercise extra caution throughout the duration of the flush,” said a bureau news release.

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