Cataloging Large Precipitation Events Associated with Atmospheric Rivers in the Upper Colorado River Basin

Amidst declining mountain snowpack across the western United States in recent years, increasing attention has been focused on the spatiotemporal trends of snowpack accumulation each season. Individual events accounting for substantial proportions of total seasonal precipitation, referred to as “large precipitation events (LPEs),” have been identified as significant predictors of subsequent streamflow in basins across the west, including the Upper Colorado River Basin (UCRB). Residual moisture from landfalling atmospheric rivers originating over the Pacific Ocean is thought to influence inland hydrology, though to a more subtle extent overall as compared to coastal regions. The contribution of atmospheric rivers to specific LPEs has not yet been widely examined in the UCRB and is therefore the focus of this study.

This exploratory study utilizes an archive of LPEs derived from observations at a sample of high elevation snow telemetry (SNOTEL) locations in the UCRB from 1981-2014 to determine and characterize the moisture delivery mechanisms common to LPEs. Existing catalogs of atmospheric rivers offer the opportunity to examine the relative spatiotemporal impacts of these moisture sources during LPEs across the UCRB. Characteristics of atmospheric river-associated LPEs will then be statistically related to various hydrometeorological variables and climatic teleconnections to begin to contextualize the importance of atmospheric rivers to the hydrology of the UCRB.