Extra snowpack boosts runoff forecasts

Despite the mild weather seen across much of the Intermountain West during the early part of February, runoff forecasts across the Upper Colorado River Basin remain well above average.

“Snowpack in several areas now exceeds the annual seasonal peak that typically occurs later in the spring months of April or May,” said the Colorado River Forecast Center.

The CBRFC February runoff forecast

snotel-map-early-feb-17

SNOTEL chart courtesy UCRBFC

using SNOTEL data (see accompanying chart) from the Natural Resources and Conservation Service calls for above-average flows across the Upper Colorado River Basin and points out the Gunnison and Dolores river basins, where runoffs may range from 125-150 percent of average. By comparison, the rest of the Colorado River headwaters forecasts generally range between 110 and 120 percent of average, says the CBRFC.

So much snow has to come down this spring that the Bureau of Reclamation announced recently a doubling of releases from Blue Mesa Reservoir on the Gunnison River, from 600 cubic feet per second (cfs) to 1,200 cfs.

“This increase is in response to the high runoff forecast for Blue Mesa Reservoir this spring,” wrote Erik Knight, hydrologist with the BuRec in Grand Junction. “The latest runoff forecast predicts 925,000 acre feet of runoff to Blue Mesa Reservoir between April and July, which is 137 percent of average.”

Knight said Blue Mesa currently is 71 percent full with 586,00 acre feet.

Lake Powell could see 9.60 million acre feet (MAF) (134 percent of average), Fontenelle Reservoir 1.20 MAF (166 percent of average), Flaming Gorge 1.65 MAF (168 percent of average), Blue Mesa Reservoir 925,000 AF (137 percent of average), McPhee Reservoir 440,000 AF (149 percent of average), and Navajo Reservoir 880,000 AF (120 percent of average).

All this means that should these forecasts hold (remember the tenuous nature of such long-term forecasts), the April-July unregulated inflow forecasts for some of the major reservoirs are impressive, to say the least.

Which means good news for the folks watching water levels in Lake Mead.

– Dave Buchanan

 

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