Atmospheric river contribution to hydroclimatic variables in the Nechako watershed
Atmospheric Rivers (ARs) form an essential component of the precipitation patterns of British Columbia's Nechako River Basin (NRB), contributing significantly to the region's hydroclimate. This study examines the contribution of ARs to total precipitation, rain, snow, and snow water equivalent (SWE) in the NRB by analyzing two climate databases, namely the six-hourly AR Catalogue of Gershunov et al. (2017) and the hourly climate data of the ERA5-Land product (Muñoz-Sabater et al., 2021), which are associated on a daily scale. Data from 1950 to 2021 reveal that ARs account for 21-25% of the annual precipitation totals in the westernmost sub-basins of the NRB, with the Upper Nechako and Stellako being most affected. A longitudinal reduction pattern in the contribution of ARs is observed across all variables. ARs markedly influence rain totals more than other variables, particularly during fall, where nearly half of the rainfall is attributed to ARs, while only 24% is to snowfall. AR-related snow represents a higher proportion of seasonal totals during fall than winter due to higher regional AR frequency and intensity from September to November. Nearly 20% of the snow in the Upper Nechako and Upper Stuart is linked to ARs, while AR-related SWE is higher in the Upper Stuart. These findings demonstrate the critical role of ARs in shaping the hydroclimate of the NRB and highlight the importance of understanding their relationship with the hydrological cycle for the long-term sustainable development of Western Canadian watersheds.