In a perfect world, with rain and snowfall adequate to every season, Bighorn Lake and the Bighorn River below it would be in perfect shape. And all the people who manage them, use them and build their lives around them would be happy. Even the fish would be happy.
If you get 100 percent of normal snowpack and 100 percent of spring and summer rains - and get it every year - managing water is easy.
Unfortunately, the real world doesn't work that way. In spite of statistics for its "normal" condition, the semi-arid West lives in a landscape of precipitation booms and busts. Lately, it's mostly been busts.
These busts have left factions in Montana and Wyoming warring over water on the Bighorn in the waning months of 2006.
At the head of Bighorn Lake, Wyoming interests want more water for the lake to provide recreation and boost tourism dollars flowing into Lovell. Montana interests want to preserve the blue-ribbon trout fishery of the Bighorn River below Yellowtail Dam and the multimillion-dollar tourism industry there.
Caught in the middle are the water managers, trying to craft plans to satisfy as many people and competing interests as possible.
"It's not an exact science," said Tim Felchle, hydraulic engineer in the Reservoir and Rivers Operations Branch of the Montana Area Office of the Bureau of Reclamation in Billings.
"If we could accurately predict inflows to where they're going to turn out to be actual, the job would be simple. It wouldn't be a problem," Felchle said. "But what we do is prepare our forecasts - our best guess from the information we have - and then we make three plans. One is for what we have in snowpack and the normal precipitation we expect. The two other plans are for if it's drier than that and if it's two or three times as much precipitation. Those are our outer limits. Hopefully you can fall in between there."
The mixture of winter snowpack and spring and summer precipitation is what makes forecasting more difficult.
According to Roy Kaiser, water supply specialist for the Natural Resources Conservation Service based in Bozeman, melting snowpack makes up 60 to 70 percent of the inflows to Bighorn Lake.
As of April 1 of this year, snowpack figures were 80 percent of normal for the Bighorn drainage, the latest in a long string of dry years. Felchle and BuRec made their predictions off that amount, figuring in average precipitation for spring and early summer.
But then, almost no rain fell in the Bighorn River drainage.
"My biggest complaint about this past year is that we were forecasting these kinds of inflows up to April 1," Felchle said. "They said we should be able to successfully fill Yellowtail and keep our 2,500 cfs (cubic feet per second of water going through Yellowtail Dam into the Bighorn River below).
"But we weren't getting the spring precip we were supposed to be getting. We got zip for rain," he said. "We figured we were going to get 800,000 acre-feet of water from April to July. We got 520,000. Basically all the water that we got was snowpack.
"On top of that, when we didn't get the spring precip, the irrigators had to start irrigating early," he said. "That further depletes what little runoff is coming down the streams. And the inflows just crashed."
BuRec reacted by reducing flows through Yellowtail Dam in June, but that wasn't quickly enough to keep water levels in Bighorn Lake high enough to use Horseshoe Bend's boat ramp near Lovell.
Should the reaction have come more quickly? Some say yes. Some say no.
"We stalled off reducing the releases. Then we started making the reductions in June. We should have been doing it in mid-April," Felchle said. "But that's hindsight. Looking back at the information we had at the time, we did do the right thing."
BuRec performs a balancing act in managing the system, trying to provide needed waters and flood protection for a variety of users. Among the competing interests for water through Yellowtail Dam are flood control, lake recreation, reservoir and river fisheries, irrigation, power generation and industrial water for the power plants at Colstrip.
Complicating things further is Bighorn Lake's volatility.
"Bighorn Lake is in such a narrow and steep canyon. It doesn't have much surface area, and you have little evaporation compared to Tiber or Canyon Ferry," Felchle said. "You can fill Yellowtail 3 to 4 feet (in lake elevation) in a day, easy, if your releases are low. I've seen it come up 5 feet in a day.
"It doesn't take much to get 16,000 cfs coming in. If you're at inflows of 10,000 and get a good rain, and if you're only releasing 2,500 cfs through the dam, it can come up quickly," he said. "You can get the same difference on inflows on Canyon Ferry and it can only come up a half a foot or a foot per day. It's something we have to be aware of in managing that lake."
As it stands right now, lake elevations are above the forecasts.
Predicted to be 3,609.5 feet elevation at the end of November, Bighorn Lake was actually 3,611.7 feet because of better-than-expected inflows.
Outflows through Yellowtail Dam down the Bighorn River at Fort Smith are holding at 1,500 cfs, and forecasts indicate that level should hold through winter if expected snows fall.
But that has always been the problem with managing this and other reservoirs in the West: You can never say for sure how much snow you're going to get.
That's where problems on the Bighorn begin and the squabbling starts over who gets the limited amount of water available.
Contact Mark Henckel at email@example.com or 657-1395.