Flood watchMay 5, 2017 By Katie Roenigk, Staff Writer
Boysen drawn down; towns prep for water
As is clear to anyone driving by on the causeway, the Bureau of Reclamation is lowering Boysen Reservoir in anticipation of record inflows forecast for the spring and early summer.
Flooding is expected to occur upstream from the reservoir beginning this weekend. Preparations are ongoing, with both Lander and Hudson preparing flood walls to divert water away from residential areas.
The most recent predictions show 1.5 million acre feet of water will flow into Boysen through July. Lyle Myler, deputy area manager of the Wyoming area office of the Bureau of Reclamation, said that would be more water than Boysen has ever handled in a season.
The previous record was 1.3 million acre feet in 1967.
"So we believe there's going to be a lot of water coming," Myler said. "We are making space."
Boysen currently is about 60 percent full, which, from the causeway, makes it appear empty. The bulk of the water is about 15 north, close to Boysen Dam.
"You can see the river channel starting to show up there ... at the very upper end of the reservoir," he said. "As the water level comes down, it exposes those flats that are typically under water when the reservoir is full. (But) the reservoir hasn't been drained."
Instead, he said, the Bureau of Reclamation has simply drawn down portions of Boysen so it can be filled by the high inflows without requiring major releases downstream.
"The space we're making in the reservoir now ... will allow us to attenuate several days of high flows and hopefully maintain Boysen outflow at a reasonable rate," he said.
High outflows aren't good for areas downstream, like Bighorn Lake and Yellowtail Dam in Montana, Myler said. He will coordinate with Bureau of Reclamation officials who manage that reservoir throughout the season.
Upstream of Boysen, the Midvale Irrigation District manages two other reservoirs in Fremont County - Bull Lake and Pilot Butte.
Myler said Bull Lake holds about 150,000 acre-feet of water that eventually flows to Boysen. He has been in touch with district manager Jon Howell to discuss expectations for the season.
"The district is looking at the same management strategy with Bull Lake as we have with Boysen," he said. "As they see the big (inflows) come they'll step up their releases to try to manage space so when really warm temperatures come they won't have to push the outflow up as high."
He added that Bull Lake ended the year with low water levels due to the dry summer of 2016, so it now sits at about 40 percent full.
"They've been gradually filling the reservoir," Myler said.
Howell said he always tries to fill Bull Lake in order to adequately supply irrigators with water throughout the summer. With the high flows forecast this year, however, he isn't worried about meeting that goal.
"We're not terribly concerned about filling Bull Lake," he said. "We will fill it. I'm confident of that."
To protect the dam structure, he continued, he will have to let as much water flow out of the reservoir as necessary.
"It can only hold so much water," he said. "If there's a lot of water that's going to come down, which is in excess of what can be held by the reservoir, it'll have to go down the river channels. There's just no choice. ... You can't allow those reservoirs to overfill."
Midvale also manages Pilot Butte - otherwise known as Morton Lake - which is currently filled to its 40,000 acre-foot capacity.
Howell pointed out that the reservoir west of Kinnear is used solely for irrigation storage and doesn't lie along the river channel. Instead, it is fed by the Wyoming Canal.
"We have total control over what goes in and what comes out of Pilot," he said. "But the fact it's full right now basically means that it's not going to be part of the mixture in dealing with the flood waters."