Dry early winter worries McPhee Reservoir managers

Sunday, Dec. 10, 2017 3:07 PM
The Dolores and San Miguel basins, seen Dec. 2 from about 12,000 feet elevation on the Lizard Head Trail, are at 18 percent of normal for winter precipitation.

Winter is off to a slow start in the Dolores Basin, and it’s becoming a concern for McPhee Reservoir managers.

Mountain snowpack is sparse, with more brown ground showing than snowy white. Snotels situated at various elevations in the Dolores Basin are recording 18 percent of normal precipitation for this time of year, according to the National Resource Conservation Service. Last year at this time, the basin was at 122 percent of normal.

“We are concerned about lack of snowpack, but it is still early in the season,” said Mike Preston, general manager for the Dolores Water Conservancy District that manages McPhee.

A silver lining is that McPhee has strong carryover storage of 137,000 acre-feet because of above-average snowpack and runoff last winter.

Active storage of 270,000 acre-feet is needed to provide full water supply for farmers in 2018, “so we are already at half the supply needed,” Preston said.

Enough excess water for a 2018 boating release below McPhee Dam would require at least an average winter snowpack. While full farmer supply is anticipated even with a below-average winter snowpack, a weak winter could create a lack of carryover at the end of the season, putting the 2019 season more at risk, Preston said.

The U.S. Drought Monitor shows that western Colorado and eastern Utah have moved into the moderate drought category. And the dry trend is expected to continue, according to forecasts.

A strong high-pressure ridge stretching across the western U.S. is preventing storms from reaching Colorado, said Megan Stackhouse, a meteorologist with the National Weather Service.

The rest of December looks drier than normal, as the high pressure ridge is expected to stick around, she said.

Also, a La Niña weather pattern forming in the Equatorial Pacific tends to favor the Northwest with wet storms, with less precipitation for the Southwest.

“There is plenty of time to get snow, it is just slow to kick in this year,” Stackhouse said.