PHOENIX, April 5, 2011—Arizona’s mountain snowpack is melting fast due to a well below average snowpack and soaring temperatures over the past week. As a result, streamflow for the remainder of the spring runoff period is predicted to be well below normal.
“Our April 1 survey shows that most snow measurement sites have already melted, which is about a month earlier than normal,” said Dino DeSimone, state water supply specialist for USDA’s Natural Resources Conservation Service (NRCS). NRCS coordinates the measurements of snowpacks at 44 sites across the mountains of northern and eastern Arizona. “What snow remains is limited to the uppermost reaches of the basins,” DeSimone said.
Among the findings in the April 1 Basin Outlook Report, the Salt River Basin and San Francisco-Upper Gila Basin snowpacks were measured at only 5 and 6 percent of the 30-year average, respectively. The Little Colorado River Basin was at 16 percent and the Verde River Basin at 47 percent of average snow water equivalent. “The current conditions are in sharp contrast to what we saw a year ago at this time, when the snowpacks ranged from 219-246 percent of average,” DeSimone added.
For March, precipitation amounts ranged from 8 percent of average over the San Francisco-Upper Gila River Basin to 41 percent of average in the Verde River Basin. The Salt River Basin and Little Colorado River Basin had 16 percent and 30 percent of average precipitation last month, respectively.
Thanks to much more favorable conditions experienced during the previous winter, the six Salt River Project reservoirs are currently at 89 percent of system capacity, for a combined total of 2,051,000 acre-feet in storage. San Carlos reservoir on the Gila River, on the other hand, has only 95,000 acre-feet in storage or 11 percent of capacity.
The forecast calls for well below normal runoff to continue in all of the basins through May. Flows are expected to be 15 percent of median in the Salt River near Roosevelt and 43 percent in the Verde River above Horseshoe Dam. The Little Colorado River at Woodruff is forecast at 18 percent of median flows, while the Gila River at Solomon is predicted to have 21 percent of median flows. By contrast, Colorado River inflow to Lake Powell is estimated to be 120 percent of average for the forecast period April-July.
The NRCS Arizona Basin Outlook Report and other related reports are available here. For more information, call NRCS Water Resources Specialist, Dino DeSimone, at 602-280-8786.