Jun 18, 2015

Area reservoirs brimming full, but no serious flooding expected

Buffalo Bill Reservoir is nearing its fill line, and Boysen and Yellowtail reservoirs are full.

Very minor flooding has been reported in low-lying areas near Greybull, Basin and north of Lovell, but officials weren't predicting major problems.
  
Buffalo Bill was more than 97 percent full Tuesday, according to Bureau of Reclamation data.

Between May 17 and June 16, Buffalo Bill was discharging more than 1,400 cubic feet per second (cfs) in mid May. On Tuesday, it was discharging 7,216 cfs.

When this photo was taken in May, the Buffalo Bill Reservoir wasn't as full as it is now. Cody New Co. file photo by Matt Naber
Roughly 500 cfs is diverted at the the Buffalo Bill Dam to the Heart Mountain Canal, said Mahonri Williams, chief of the bureau’s water and lands division.

The 30-year June average is around 3,000 cfs, so the above figure is high, but Williams said he hasn’t heard any concerns about flooding structures downstream.

“I don’t think those flows are going to seriously hurt anything,” he said. “There’s a lot of water flowing into the Big Horn Reservoir, both from the Shoshone River and the Big Horn River.”

Yellowtail was 100 percent full Tuesday. Yellowtail was releasing more than 2,000 cfs in mid-May. It was releasing 14,242 cfs Tuesday.

Yellowtail’s release is high, but not unprecedented.

When June 2011 snowpack was high, outflow was 15,500 cfs. In 1967, June outflow from Yellowtail was 25,000 cfs, said Tim H. Felchle, the bureau’s supervisory civil engineer in Billings.

“There is no flooding downstream of Yellowtail. Everybody should be dry,” Felchle said. “But a few people are encroached on in the flood-plain area.”

All the rivers in the Big Horn Basin are higher than they normally are at this time of year, Felchle said, adding, “I’ve never seen so much water in the Big Horn Basin.”

Where the Big Horn River flows, the lowlands around Greybull and Basin are seeing minor flooding, said Williams.

“I’ve never seen so much water in the Big Horn Basin,” said the Bureau of Reclamation's Tim H. Felchle.

The girders supporting the causeway that crosses the Big Horn Reservoir north of Lovell were submerged by water in 2011, “but I don’t think we’re that close yet,” Felchle said.

North of the causeway, the water is high at the Kane boat ramp, making boat launching difficult. Mosquitoes are ferocious there too, said Christy Fleming, chief interpretive ranger at Bighorn Canyon National Recreation Area.

“The lake is still going up,” Fleming said. “Black Canyon (Campground) is under water.”

Ok-A-beh and Horseshoe Bend docks are functional, but Horseshoe’s beach is under water. Everything near the Mason-Lovell Ranch is also closed due to high water, and Fleming said she is not sure when the area will reopen.

She warned to watch out for floating driftwood and other debris in the lake.

Boysen was 100 percent full Tuesday. It had been releasing more than 700 cfs in mid-May according to a bureau data. On Tuesday it was spewing 7,521 cfs.

The region's snow appears to have almost completely melted away.

Spring runoff is declining. At sites measuring precipitation, all snow has melted or very little remains, Williams said.

April through July are the big water months, when it's hoped melting mountain snow will fill up reservoirs. April and May inflows to Buffalo Bill exceeded the 30-year average, and June may exceed the 30-year average too.

As inflows slow down later this month, the outflows will be reduced, Williams said.

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