The annual spring bump in flows coming out of Palisades Reservoir is underway, and water managers are slowly boosting water releases for at least the next few days.
Aimed at imitating the natural cycle, restoring riparian habitat and helping Snake River cutthroat trout, the “flushing flows” are increasing at a rate of about 1,000 cubic feet per second each day and had climbed to 14,500 cfs by midday Friday. Flows are scheduled to top out at 19,000 cfs by June 8, and then be reduced 5 percent a day to 13,000 cfs.
The potential for trees getting swept into headgates and bridges could change those plans, Bureau of Reclamation water operations manager Mike Beus said.
“If after 16,000 cfs on Sunday morning we hear from the irrigators that we’re having debris problems … we would truncate the operation and ramp back down,” Beus said.
The flushing flows are designed to coincide with the peak period of snowmelt and inflow, so the operation does not figure to significantly draw down Palisades Reservoir. As of Friday, Palisades’ 1.2 million acre-feet of storage were 83 percent full.
Releases out of Jackson Lake, at 94 percent full, have held steady at 3,250 cfs for the past week. The Bureau of Reclamation bumped up outflow into the Snake the last week of May.
Boaters and fishermen who may be floating or wading the Snake are urged to be wary of high water and snags that get moved around by increased flows.
Beus said the peak flows in coming days will likely exceed previous peaks, which occurred nearly a month ago.
“Spring is starting over,” he said. “High tributaries like the Buffalo Fork are increasing dramatically and we think we’re going to nail this peak right on.”
Snake River levels at Alpine, 11,000 cfs on Friday, were higher the last two or three days than the last time the unregulated flows peaked, Beus said.
One objective of the highly regulated springtime flows on the South Fork is to help native cutthroat compete against non-native rainbow trout between Palisades Dam and the mouth of the Henry’s Fork. The Idaho Department of Fish and Game has set a goal to reduce rainbow trout to 10 percent of all trout on that stretch, but in recent years’ surveys they’ve accounted for about 30 percent.
This article appeared on the Jackson Hole News & Guide website on June 4, 2016.