Spring runoff low, but reservoirs high | VailDaily.com

Spring runoff low, but reservoirs high

EAGLE COUNTY, Colorado – The spring runoff will be the lowest in a decade and maybe the lowest in recorded history, say scientists keeping a wary eye on Colorado’s snowpack.

Warm weather in April shrank the statewide snowpack from 52 percent of average to just 19 percent, according to the latest statistics from the Natural Resources Conservation Service, a division of the U.S. Department of Agriculture.

However, all is not lost. In the Upper Colorado River basin, where we live, reservoir storage is 127 percent of average and 119 percent of last year’s record amounts.

“Luckily Colorado’s reservoir storage is in better condition than it was in 2002,” said Phyllis Ann Philipps, state conservationist with the Natural Resources Conservation Service. “This stored water should help alleviate late-summer shortages.”

Snowpack traditionally peaks on April 12, Phillips said.

This year’s snowpack was dramatically below average and melted out an average of five weeks early at sites below 10,000 feet, Phillips said.

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On average, streamflows will be 45 percent of normal across the basin, the the conservation service said.

“As the disappointing winter of 2012 draws to a close, the state’s water managers prepare for what will likely be one of the lowest runoff years since 2002,” said the NRCS report. “March and April’s snowfall and precipitation totals were extremely low across the state. This coupled with abnormally warm spring weather sent the snowpack into an early melt cycle in March.”

In the Upper Colorado River Basin, the May 1 snowpack is the lowest in the 45 years record have been kept, the the conservation service report said.

At only 21 percent of average, the current snowpack is 6 percentage points lower than the previous record low set in 2002, when the snowpack was reported to be 27 percent of average, the report said.

The snowpack in the Colorado River basin dropped 28 percent in April. For the sixth month in a row the Colorado River basin received below average mountain precipitation. April precipitation was just 61 percent of average, and total precipitation for the year dropped to 68 percent of average.

Five of the last seven months have seen below average precipitation totals.

Most of the annual streamflows in the western United States start as snow falling during the winter and early spring. As the snowpack accumulates, hydrologists estimate the runoff that will occur when it melts.

They measure that snow water equivalent at several sites, including one on Vail Mountain.

The anomaly of this year is magnified when compared to last year; the current snowpack is only 14 percent of last year’s May 1 record totals.

The current snowpack percentage matches the state’s record low, set in 2002.

And it could be worse.

The state’s lowest snowpack is 15 percent of average in the Upper Rio Grande basin. The Yampa and White basins are 17 percent of average and the Gunnison River basin at 18 percent of average.

The basins with the highest snowpack totals were the North Platte, South Platte and Arkansas; reporting 27, 25 and 25 percent of average respectively.

Nearly half of the NRCS’s SNOTEL monitoring sites had completely melted out by May 1, four to six weeks earlier than normal.

Only sites above 10,000 feet in elevation had measurable snow remaining during the May 1 surveys.

Staff Writer Randy Wyrick can be reached at 970-748-2935 or rwyrick@vaildaily.com.