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Published January 23, 2013
Southwest Snowpack(data through 1/16/13)
Data Source(s): National Water and Climate Center, Western Regional Climate Center
Scant precipitation in most of the Southwest is leaving many mountainous regions with lower than average snowpack, particularly in Colorado and New Mexico watersheds. Since the water year began on October 1, precipitation in in the Rio Grande head waters in southern Colorado has measured 62 percent of average. As of January 17, the water contained in the snowpack, or snow water equivalent (SWE), measured at eight SNOTEL monitoring sites in the Rio Grande headwaters is 64 percent of average. This is discouraging news for the water supply on the Rio Grande, which receives a large fraction of its annual supply from this watershed. Elephant Butte Reservoir, for example, contains less than 7 percent of its full capacity. Elsewhere in New Mexico, all major basins are experiencing below-average SWE (Figure 8) with the exception of Rio Hondo in the far north-central part of the state (not shown). SWE in most of these basins measures less than 75 percent of average.
Drier-than-average conditions also dominate in the upper Colorado River basin. SWE measured at SNOTEL sites in major watersheds that contribute to the Southwest’s most important river all are less than 72 percent of average. Arizona, on the other hand, is experiencing above-average SWE in the Verde River basin, central Mogollon Rim region, Little Colorado River, and upper Salt River despite slightly below-average precipitation in these watersheds since the water year began.
As a large fraction of winter precipitation typically falls between mid-January and the end of March, the next several months will be critical for determining the fate of snowpacks, and consequently, the water supply.
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.
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