Declining Snowpack Depths and Snow Water Equivalent at Snowpack Monitoring Sites in the Rocky Mountain Region, USA, 1993-200

Recent studies indicate the widespread decline of snowpack depths and snow-water equivalent in the western USA. Since 1993, the US Geological Survey, National Park Service, and USDA Forest Service have operated a network of up to 62 snowpack-chemistry-monitoring sites at elevations above 1,500 meters in the Rocky Mountain region. Two 8-year periods before and during the 2001-2008 drought indicate significant decreases in both snowpack depth and SWE. Further comparisons of trends in the Northern, Central, and Southern Rockies subregions yielded moderate to highly significant declines in snowpack depth and SWE in only the Central Rockies. Regionally decreasing trends in SWE were more pronounced at lower-elevation sites than at higher-elevation sites, however, trends in both snowpack depths and SWE were decreasing with moderate significance at higher-elevation sites during the study.