As Brad Judy stood at the head of a side channel of the Bighorn River fly-fishing for trout Wednesday, he looked downstream and saw the water had begun to boil with fish.
"I could literally see the side channel shrink in size," said Judy, who is from Washington state. "It looked like a salmon run. Hundreds of them were rushing to get out of there."
The river dropped precipitously at about 12:30 p.m. near a spot called the "Meat Hole" where Judy was fishing. A nearby pontoon boat that had been pulled up on shore was left 10 feet from the water, he said.
"I saw fish certainly scared, panicked and freaking out," he said.
Other anglers reported small trout stranded and flopping on land after the quick drop.
The abrupt loss of about 2,500 cubic feet per second of water - almost three-quarters of the river's total flow - was caused by the malfunction of new automated gate equipment at the Yellowtail Afterbay Dam caused by an electrical surge, according to the Bureau of Reclamation.
During the failure, the river's flow fell from around 4,000 cfs to 1,500 cfs for about 45 minutes. An alarm warned workers at Yellowtail Dam who quickly reacted to remedy the drawdown.
"The afterbay automation system has been undergoing pre-commissioning testing for a couple of weeks now, and as this incident demonstrates, automation systems can unfortunately be vulnerable," Dan Jewell, Montana area manager for BuRec, said in a statement. "We believe this malfunction was triggered by a significant electrical surge, but regardless of the cause, it points out the need for additional fail-safe mechanisms in our control system."
The quick drop in river flows left many young fish stranded on shore.
"Although we've already taken steps to ensure a similar malfunction doesn't occur again, that doesn't change the fact that the fishery resource was likely impacted - to what extent we won't likely know immediately," Jewell said.
"We're still trying to assess what it means to the fishery," said Bob Gibson, Fish, Wildlife and Parks information officer in Billings.
He added that smaller trout that live near the margins of the water would be the most severely affected by any rapid drawdown, since larger fish would typically be strong enough to swim out of the shallow water.
Pat Straub, who works as a caretaker at a fishing lodge about six miles below the dam, said he saw trout fry stranded when the water dropped 4 to 5 feet.
"I walked to the bank and there were small fry flopping around," Straub said. "I did my best to chuck them back in."
Doug Haacke of the Friends of the Bighorn River received an e-mail from Bighorn River guide Dave Opie alerting him to the situation. Opie said he and his clients attempted to return hundreds of trout fry to the water.
The dramatic drawdown comes as water users continue a tug-of-war over allocation of water in Bighorn Reservoir. The debate has pitted anglers and fly-fishing guides on the Bighorn River against Lovell, Wyo.-area reservoir users. Mixed into the fray is the National Park Service, whose Bighorn Canyon National Recreation Area surrounds much of the reservoir. The Bureau of Reclamation is caught in the middle, trying to keep flows in the river high enough to create plenty of habitat for the Bighorn's multimillion-dollar trout fishery while also keeping reservoir users happy and providing for electric power generation.
"What we've been pressured to do is squeeze more and more out of both ends of the system," Jewell said.
The struggle has risen to Congress, where U.S. senators from Wyoming and Montana have stepped into the tussle over the border-crossing reservoir.
The past two years, the bureau has held more water back to fill Bighorn Reservoir, even reducing flows to 2,415 cfs this spring despite forecasts of a heavy spring runoff. Once the runoff started, the dam had to release unusually heavy flows to accommodate the high influx of water. The releases in late June peaked at 13,000 cfs - a 14-year high - causing flood damage to one state fishing access site.
Earlier this week, the Bureau of Reclamation told its Bighorn user group that it would manage the dam for a 20-foot storage range in lake elevation, a Park Service recommendation.
"Using such a narrow window dooms the river to be at minimum flows most of the year, and then flooding during spring runoff," said Haacke, of the Friends of the Bighorn River. "It's time for the Reclamation and the Park Service to acknowledge they're negatively impacting a robust fishery and an important part of the economy."
Fish, Wildlife and Parks prefers to see the river's flow maintained at a minimum of 2,500 cfs.
To meet its targets, BuRec will drop the river to 3,000 cfs next week. The lake's current elevation is 3,644 feet. The Park Service's minimum recommended lake level is 3,620 feet.
"We're looking at insuring that we have as much storage as possible for fall and winter releases," Jewell said. "We'd like to go into fall with 3,640 - full pool."
Contact Brett French at firstname.lastname@example.org or at 657-1387.