Southwest Snowpack

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.