Snowpack Melting Fast: Heavy Runoff Now, Low Runoff for Spring

PHOENIX, March 6, 2009—Arizona’s mountain snowpack is melting fast due to above average temperatures and below average precipitation during the past few weeks. As a result, rivers and streams throughout the state are currently flowing fast and furious. This also means that streamflow for the spring runoff period (March-May) is predicted to be well below normal.

“Our snowpack peaked early in the winter, but our March 1 survey shows that much of the snowpack has melted,” said Dino DeSimone, state water supply specialist for USDA’s Natural Resources Conservation Service. NRCS coordinates the measurements of Arizona’s snowpacks at 41 sites across the state and reports its findings in the Arizona Basin Outlook Report published throughout the winter.

Historically, the beginning of March shows the maximum snow accumulation for the year. Although the statewide snowpack is currently at 111 percent of the long-term average, several sites have no snow, and the aerial extent of the snowpack is limited to the uppermost reaches of the basins. “What snow remains is rapidly melting and the outlook for more precipitation in the coming months is poor,” DeSimone said.

Among the findings in the report, the Salt River Basin snowpack was measured at 93 percent of the 30-year average and the Verde River Basin at 121 percent of average. The San Francisco-Upper Gila Basin was measured at 54 percent of average and the Little Colorado River Basin at 117 percent of average snowpack as of March 1.

For February, precipitation amounts were 76 percent of average over the Salt River Basin, 109 percent of average over the Verde River Basin, 47 percent of average over the San Francisco-Upper Gila River Basin, and 93 percent of average over the Little Colorado River Basin.

Overall, the six Salt River Project reservoirs held a combined total of 2,224,000 acre-feet in storage at 96 percent of system capacity. San Carlos reservoir held 231,000 acre-feet in storage as of March 1, which is 26 percent of capacity.

Long-range predictions call for well below median runoff for the March-May forecast period. Flows over these three months are expected to be 63 percent of median in the Salt River and 54 percent in the Verde River. Forecasts call for 45 percent of median flows in the San Francisco at Clifton and the Gila River is forecast to run 33 percent of median at Safford.

The Little Colorado River at Woodruff is forecast at 33 percent of median inflow. Colorado River inflow to Lake Powell is estimated at 98 percent of average for the forecast period April-July.

The Arizona Basin Outlook Report is available at: http://www.az.nrcs.usda.gov/snow/. For more information, call NRCS Water Resources Specialist Dino DeSimone at 602-280-8786.


 

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