Above-average snowpack promises to fill McPhee Reservoir and increases the chance of a whitewater boating release on the Dolores River below the dam.
Winter snowfall in the Dolores Basin is at 136 percent of normal as of March 26. When it all releases in the coming months, it will top off the reservoir, and irrigators will receive a full supply, said Mike Preston, general manager for the Dolores Water Conservancy District.
The good news for boaters is that runoff predictions show there is a decent chance for a two- to four-week boating season beginning in May if the current storm track continues.
The reservoir is in recovery mode after last year’s dry winter, Preston said.
“We started out pessimistic, but this winter’s snowfall has been a surprise and a delight,” he said.
McPhee is near dead-pool status at just 14,000 acre-feet of active supply but is expected to reach the full 240,000 acre-feet active supply.
According to the Colorado River Basin Forecast Center, there is a 70 percent probability that Dolores River runoff will produce 40,000 acre-feet beyond what the reservoir can hold. That equals an approximate two-week whitewater release beginning in late May. Peak flows would be would between 2,000 cubic feet per second and 2,500 cfs.
A 50 percent runoff probability shows 130,000 acre-feet beyond what the reservoir can hold, according to the Forecast Center, enough for a four-week whitewater release beginning in early May.
“My instinct is that it will be something in between those two ranges,” Preston said, adding that a more definitive forecast will be available by mid-April.
Spill flows and timing would be managed for optimum boater experience, based on boater input, ecological and reservoir management priorities, Preston said.
The release also has environmental benefits for the river below the dam. High flows mimic the river’s natural hydrology, flush accumulated sediment, and deepen pools relied on by native fish during low water times.
Colorado Parks and Wildlife biologists work with reservoir managers to time the spill in a way that does not disrupt the native fish spawning cycle.
A dam operations meeting that focuses on boating releases below the dam will be on April 18 at the Dolores Community Center at 7 p.m.