Low Arizona surface water supplies likely this spring and summer

Warm weather intermingled between a few winter storms moving through Arizona'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, water supply specialist for USDA's Natural Resources Conservation Service-Arizona office.

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.

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.

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.

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.

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

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