John Crowley is getting a bit anxious.
It’s nearing the middle of May and the reservoir behind the dam at Lake Como has yet to fill.
On Friday, it was only 67% full.
As the manager of Bitter Root Irrigation, Crowley’s job is to make sure that irrigators from one end of the Bitterroot to the other have enough water to irrigate their crops. This time of the year, it’s a juggling act.
Right now, he needs another 12,634 acre-feet of water to fill Lake Como. According to the best calculations available, there’s about 65,000 acre-feet of water stored in the snowpack above the reservoir. An acre-foot is the amount of water it takes to cover 1 acre of land 1 foot deep.
“If the numbers are accurate, we should be fine,” Crowley said. “We like having these cold nights to slow down the melt, but as an irrigation district manager, it can make you a little bit anxious.”
In the 14 years that he’s served in that position, Crowley can honestly say that no two seasons have ever been the same.
“Mother Nature is a worthy chess opponent,” he said. “You think you got her figured out and then she does something completely different. She counters your every move.”
Bitter Root Irrigation started releasing water from the reservoir into the Big Ditch on April 29. They also began diverting some water from several tributaries along the east side of the valley as they do every year.
The challenge Crowley faces is keeping enough water in the ditch to meet demands, but not adding more than the ditch can handle.
“It seems like everything is about a month behind this year,” he said. “Farmers are barely getting their seed into the ground. Some of the big gravity systems from Corvallis downstream haven’t turned on yet. So we have to be careful not to get too much water in the ditch between Corvallis and Burnt Fork.”
But now temperatures are set to soar this weekend and then cool right back down next week.
“Once that happens, everyone will want to turn on and start irrigating,” Crowley said. “It’s the nature of the beast, but people need to understand that it can take time to meet those demands. They have to be patient.”
Crowley is trying his best to practice a little bit of patience, too, when he looks the inflows coming into Lake Como.
“We really haven’t had any heavy inflows into the reservoir quite yet,” he said. “They have been in the 300 to 400 cfs (cubic feet per second) range. We haven’t had any of the 800 to 900 cfs inflow yet, which would help fill the reservoir pretty quick.”
“I would just like to have it a little fuller right now,” Crowley said. “If I had this snowpack with an almost full reservoir, it would be just about perfect.”
Bitterroot National Forest hydrologist Andy Efta said the high elevation is hanging right in there at normal over the 30-year average.
“If we get a spike in temperatures, there’s certainly some potential for the river and creeks to start running pretty high,” Efta said. “It’s going to be interesting over the next couple of weeks to see whether we get enough water for the river to start jumping the bank or whether it will go up and come down gradually.”
The cool spring helped both in keeping low-lying areas from flooding earlier in the season and not allowing the high elevation snows from disappearing too soon.
“Right now, you couldn’t ask for anything much better at this point, but we’re going to have to wait and see what happens,” Efta said.
Historically, the spring runoff in the Bitterroot River peaks toward the end of May.
Efta said the gauge at Darby showed a couple of early peaks in April when the low-elevation snowpack melted, but since then it’s been hovering close to the median daily flows that have been recorded over the past 70 years.
The U.S. Department of Agriculture Natural Resources Conservation Service said the combination of the snow water equivalent in the snowpack and the near average precipitation for the year through the month of April led to a forecast that calls for near to slightly below average streamflows in the Bitterroot River through July 31.
But that forecast came with a caveat.
“Late spring and early summer precipitation play a critical role in these flows, so even though it’s good news, don’t rest your laurels just knowing the snowpack peaked near normal,” said the service’s monthly snowpack and water supply outlook report. “The next month or two will tell us a lot about our resources later in the summer. For now, we’re on the right track.”