HELENA — When officials with the Bureau of Reclamation began holding back water to fill Canyon Ferry Reservoir earlier this month, the Missouri River flow below Holter Dam dropped more than 45 percent in less than a week. Now that dramatic drop has Montana Fish, Wildlife and Parks concerned about the potential impacts on trout and other fish in the blue ribbon fishery.
With trout having already spawned, flows in the Missouri had peaked at 11,000 cubic feet per second by June 2. The next day the flow fell to 7,000 cfs, and by June 6, just above 5,000 cfs, according to flow data from the U.S. Geological Survey.
Following the sudden drop, reports from anglers of dried-up spawning beds and fish stuck inside pools began to come into FWP, said fisheries biologist Eric Roberts.
“I’ve heard from a few fishermen and there is a concern there — flows were so high for so long,” he said. “It’s hard to monitor, and it’s a tough situation from a water-management perspective, but we raised our concerns with the bureau.”
FWP, the Bureau of Reclamation and other stakeholders on the river get together every March to discuss the runoff situation, and that meeting usually has good communication among the agencies, Roberts said.
Such a major change in flow in such a short period of time is not a normal occurrence on the river, and the earlier high flows were easily justifiable given the high-mountain snowpack, he said.
“It’s tough duty predicting what Mother Nature is going to do,” Roberts said. “Going forward, I can see them working to improve our coordination again.”
The bureau confirmed that the sudden drop in flows was not a normal occurrence, especially so early in the year.
“Typically our peak flows into Canyon Ferry happen in the second or third week of June,” said Stephanie Micek of the bureau’s Water Operations Division. “We didn’t anticipate inflows would reduce as much as they did as soon as they did.”
The drop of inflows into Canyon Ferry came from a lack of rain through all of May. Besides maintaining flows during the spring and early summer, the bureau has an obligation to maintain flows throughout the expected drier months of July, August and September. That left officials at the bureau with a tough decision to make in a short period of time, Micek said.
The bureau needs to keep a flow above 4,100 cfs to ensure aquatic health and recreation opportunities in the Missouri. If it continued to release water in high amounts with inflows dropping, the bureau could not guarantee desired flows into typically drier days ahead, Micek said.
“It’s a tradeoff, and if you don’t cut flows now you’ll get cut below desired levels into the summer and fall,” she said.