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Published November 21, 2012
Southwest Snowpack(data through 11/15/12)
Data Source(s): National Water and Climate Center, Western Regional Climate Center
Most basins in Arizona and New Mexico had below-average snow water equivalent (SWE) as of November 15 (Figure 8). However, a few basins exhibit above-average conditions as a result of a recent storm. In the Upper Salt River Basin in the White Mountains, for example, SWE now measures 1,350 percent of average. In New Mexico, the San Francisco and the Gila River basins had 600 and 900 percent of average SWE, respectively. These numbers should be viewed cautiously because it is early in the season and as a result even small snow accumulations can cause large deviations from the average.
In the states to the north, which supply most of the water to the Colorado River and the Rio Grande, conditions are mixed. Snowpack levels in Colorado are well below average, ranging from 50 to 64 percent of average SWE, while SWE in Utah ranges from 90 to 263 percent of average. With well below-average storage in many New Mexico reservoirs, it is crucial that precipitation this winter is robust. Combined reservoir storage in New Mexico totals 1.6 million acre-feet and stands at about 19 percent of capacity. A similar picture can be seen in Arizona, where the San Carlos and Salt and Verde reservoirs only contain about 36 percent of their combined 3.2 million acre-feet.
The January–March precipitation outlook recently took a turn toward drier conditions, in part because the once-budding El Niño stalled. The NOAA-Climate Prediction Center (CPC) now calls for increased chances for below-average rain and snow in most of Arizona and New Mexico. However, the forecast for the Upper Colorado and Rio Grande basins calls for equal chances for above- and below-average precipitation.Notes:
Snowpack telemetry (SNOTEL) sites are automated stations that measure snowpack depth, temperature, precipitation, soil moisture content, and soil saturation. A parameter called snow water equivalent (SWE) is calculated from this information. SWE refers to the depth of water that would result by melting the snowpack at the SNOTEL site and is important in estimating runoff and streamflow. It depends mainly on the density of the snow. Given two snow samples of the same depth, heavy, wet snow will yield a greater SWE than light, powdery snow.
This figure shows the SWE for selected river basins, based on SNOTEL sites in or near the basins, compared to the 1971–2000 average values. The number of SNOTEL sites varies by basin. Basins with more than one site are represented as an average of the sites. Individual sites do not always report data due to lack of snow or instrument error. CLIMAS generates this figure using daily SWE measurements made by the Natural Resources Conservation Service.
Southwest Climate Outlook Staff
- Michael Crimmins, UA Extension Specialist
- Stephanie Doster, Institute of the Environment Editor
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, Managing Editor, CLIMAS Associate Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Dollin, CLIMAS Publications Assistant
- Dave Dubois, New Mexico State Climatologist
Please direct your Southwest Climate Outlook comments and suggestions to Zack Guido.
The CLIMAS Web site contains official and non-official forecasts, as well as other information. While we make every effort to verify this information, please understand that we do not warrant the accuracy of any of these materials.... Read full disclaimer