BIGHORN RESERVOIR

New plan soothes Bighorn water worries

Bureau of Reclamation tries to please lake users, river anglers with dam plan
2010-09-29T17:44:00Z 2010-09-29T18:35:10Z New plan soothes Bighorn water worriesBRETT FRENCH Of The Gazette Staff The Billings Gazette
September 29, 2010 5:44 pm  • 

There seems to be a truce on at least one front of the Wyoming-Montana water wars.

Bighorn Reservoir users in Wyoming and trout anglers on the Bighorn River below the reservoir's Yellowtail Dam in Montana seem pleased with a new operating plan designed by the Bureau of Reclamation.

"I think mostly we're just glad to see the cooperation," said Ken Frazer, fisheries manager for the state Department of Fish, Wildlife and Parks in Billings.

"We're way ahead of the game where we were five years ago," agreed Bob Croft of Lovell, Wyo., a director of the Friends of Bighorn Lake user group. "Everyone is trying to work together for the common good. That's a big accomplishment."

The draft report was the topic of a daylong meeting among anglers, outfitters, lake users and agency officials on Tuesday in Billings. The cooperative group was formed in 2007.

Another public meeting is scheduled Oct. 7 to discuss the fall and winter operating plan for Yellowtail Dam. That meeting will be held at 6:30 p.m. in the Montana State Univeristy Billings Downtown Conference Room at 2804 Third Ave. N.

 

The battlefield

 

The 35-page "Draft Bighorn Lake Operating Criteria Evaluation Study and Report" goes into great detail summarizing the reasoning behind the agency's proposals in what was a divisive debate between Montanans and Wyomingites, lake users and river anglers.

Bighorn Reservoir begins in Wyoming near Lovell and extends across the border north and east into Montana. The Yellowtail Dam backs up water 70 miles, including a 60-mile stretch of rugged canyon land. The land surrounding the canyon is managed by the National Park Service as a National Recreation Area. The Crow Reservation encircles the recreation area and the river below the dam all the way to Hardin.

The Bureau of Reclamation's allocation of the water has been a point of dispute. Lake users want water held in the reservoir to guarantee access to the Horseshoe Bend boat ramp on the southwestern end of the lake in Wyoming. During drought years from 2000 to 2007, the ramp was often left high and dry.

River anglers in Montana want flows to stay above 1,500 cfs, a minimal flow to protect trout populations in the world-renowned fishery. FWP has identified 2,500 cfs as the optimum flow for the river's fish with 1,000 cfs the bare minimum.

 

Water management

 

Caught in the middle is the Bureau of Reclamation.

Allocating water is not an easy job, especially considering the vagaries of Western weather. A dry winter, such as Montana experienced this year, was offset by an unusually wet spring and summer.

"This year demonstrated that no matter how well prepared you are, there's no way of predicting how the weather will turn out in the long run," said Dan Jewell, area manager for Reclamation's Montana Area Office. "Runoff this spring was almost double what was predicted. How do you plan for that?

"That uncertainty or variability is almost impossible to plan for," he said.

Under BuRec's new plan, the reservoir's water level would be kept 3 to 8 feet higher on average during the late winter and early spring. By doing so, the reservoir has a better chance of filling up during spring runoff and flows can be steadier in the river. Under its plan, the reservoir level would be 3,640 feet elevation during the summer, dropping to 3,630 feet by the end of November and 3,605 to 3,614 by the end of March, depending on mountain snowpack.

Sedimentation buildup at the head of the reservoir has raised the amount of water needed to keep Horseshoe Bend boat ramp usable. Originally, the ramp could be used down to 3,590 feet. Now the ramp is no longer useable when the water drops below 3,617 feet. The National Park Service and Wyoming Game and Fish have lobbied to keep lake levels in the summer at 3,630 and above 3,620 the rest of the year. When the water drops below 3,620, Wyoming Game and Fish said, the reservoir's fishery suffers.

"Flexibility must be built into reservoir operations to account for a wide variation in rainfall-produced runoff," the plan stated. "Until our ability to predict the weather improves significantly, there will remain a large amount of uncertainty in the spring runoff forecasts."

Even calculating snow runoff is difficult because most monitors are below the mountaintops, BuRec's plan points out. Monitors may show no snow left in the mountains, yet substantial snowpack could be left at elevations above the monitors.

And while snow accumulation is a basis for calculating runoff, since it is there and measurable, rain accounts for 25 to 30 percent of spring runoff in the Bighorn Basin. This year, it amounted to much more than that.

In early April the inflow forecast for Bighorn Reservoir was predicted to be 625,000 acre-feet, or 57 percent of average. By mid-May, wet weather had altered the inflow to 1.12 million acre-feet, or 98 percent of average. That left BuRec scrambling because it had initially taken a conservative view of the spring runoff. To compensate for the change in inflows, dam releases jumped from 2,000 cfs in April to 10,000 cfs by mid-June. The reservoir's elevation peaked at 3,645 feet by July 4.

 

River flows

 

Although this year was unusual, the new parameters defined in BuRec's plan should allow the dam to maintain a minimum 1,500 cfs flow, or higher, in the river below "100 percent of the time." The flow would be increased in the spring and early summer when rainbow trout spawn.

In addition to meeting recreationists' demands, BuRec also predicted that the new operational rules will increase the dam's power generation by about 2 percent annually.

Jewell said developing the new operating plan with the help of users has made the document better.

"But there's always room for improvement," he said.

"It will be interesting to see in the next year if our predictive models play out and we're able to make some progress," he said.

Contact Brett French at french@billingsgazette.com or 657-1387.

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