Atmospheric Rivers and Snow Accumulation in the Upper Colorado River Basin

We utilized a macroscale hydrology model in conjunction with an atmospheric river (AR) catalog to evaluate AR-affected snow accumulation in the Upper Colorado River basin (UCRB) headwaters for water years 1951-2015. We find that there are on average 11.4 days during which AR-originating snow accumulates in the UCRB each year, yielding 5.75 km(3) of snow water equivalent (SWE). This AR-originating SWE accounts for 30.8% of average annual peak SWE in the basin. Most of the ARs that reach the UCRB first intercept the Sierra Nevada region of California; 84% of days affected by ARs in the UCRB are also AR-affected days in the Sierra Nevada. The pathways of the ARs reaching the UCRB do not have a great effect on snow accumulation, however ARs that first pass through the Sierra Nevada generally produce greater snow accumulations there than in the UCRB.