Low Surface Water Supply Likely this Spring and Summer

Contact: Renee Bodine (602) 280-8778
or George Couch (602) 280-8806   

PHOENIX, March 6, 2007 - Warm weather intermingled between a few winter storms moving through the state’s high country in February has kept watershed snowpack levels below average and the water supply forecast sparse for spring.

“Our mountain snowpacks never reached average conditions this winter,” said Larry Martinez, state water supply specialist for USDA’s Natural Resources Conservation Service. NRCS coordinates the measurements of Arizona’s snowpacks at 38 sites across the state and reports its findings in the 2007 Arizona Basin Outlook Report published throughout the winter. The federal agency, through its cooperative snow surveyors, monitors snow levels in the mountain watersheds to estimate the amount of surface water available to help water users and managers plan for the future.

The March 1 report historically shows the maximum snow accumulation for the year, but this year the statewide snowpack is at 71 percent of the long-term average. The El Nino predicted to bestow at least average snowfall on Arizona never panned out. “There is diminishing hope each day that passes for significant improvement to the state’s snowpacks as springtime approaches March 20th and warm temperatures continue to melt the snow early,” Martinez said.

Tom Pagano, NRCS chief hydrologist for Arizona agrees. “What snow is there has started to melt in earnest, and we don’t foresee any more precipitation for at least a week or more. A month ago, if you were to tell me that we would be seeing red flag fire-danger warnings in Arizona the first week of March because of temperatures near the 80s and humidity in the single digits, I probably wouldn’t have believed it,” he said.

Cumulative precipitation for the current water year, October-February, remains below average in the northern watersheds, ranging from 48 to 75 percent of the long-term average. October records show significant precipitation at the automated SNOTEL sites, which turned very dry across the region in November until the Nov. 28 winter storm that brought two to eight inches of snowfall to the mountains. December produced some snow flurries, however, NRCS records show precipitation totals below 50 percent of average for the month. January brought the first significant snowfall of the season to Arizona and it seemed the weak El Nino would finally deliver heavy snowfall to the high country, but February turned dry with only marginal snow accumulations in the watersheds.

Among the findings in the report, the Salt River basin snowpack was measured at 77 percent of the 30-year average, the Verde River basin at 58 percent of average, and the San Francisco-Upper Gila basin at 87 percent of average. The southern headwaters of the Little Colorado River basin had 70 percent of average snowpack on March 1, while the central Mogollon Rim was at 80 percent of average. In the Chuska Mountains of northeastern Arizona, snowpacks were monitored by the Navajo Water Management Branch at 85 percent of average. At the San Francisco Peaks the snowpack was measured at 64 percent of average.

For February, precipitation amounts were 68 percent of average over the Salt River basin, 46 percent of average over the Verde River basin, and 70 percent of average over the San Francisco-Upper Gila River basin. The Little Colorado River basin received 72 percent of average precipitation in February.

March 1 reservoir storage remains steady for the most part compared to January 1 levels. “Carryover storage from last year will help this season, especially now that we are almost certain of below normal runoff into the major streams we all count on for our water supplies,” said Martinez.


Overall, the six Salt River Project reservoirs held a combined total of 1,426,380 acre-feet in storage at 62 percent of system capacity. San Carlos reservoir held 286,000 acre-feet in storage March 1, which is 33 percent of capacity. Lake Pleasant held 721,803 acre-feet of usable storage March 1. Storage in Lyman Lake was 7,570 acre-feet. An acre foot of water equals 325,851 gallons and is enough to supply two families for a year.

Long-range predictions call for below median runoff for the March 1-May forecast period. Flows over these three months are expected to be 46 percent of median in the Salt River, 42 percent in the Verde River, and 46 percent in Tonto Creek. Forecasts call for 67 percent of median flows in the San Francisco at Clifton Arizona. The Gila River is forecast to run 57 percent of median at the head of Safford Valley. At San Carlos, inflow to the lake is forecast at 47 percent of median through May. The Little Colorado River is forecast at 62 percent of median inflow to Lyman Lake through June. Colorado River inflow to Lake Powell is estimated at 71 percent of average for the forecast period April-July, typically the time of year when the greatest runoff occurs from snowmelt to replenish the river.

The Arizona Basin Outlook Report is available at: http://www.az.nrcs.usda.gov/snow/.

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