Influence of atmospheric rivers on precipitation variability in British Columbia’s Gaat Héeni (Silver Salmon River) Watershed

Atmospheric Rivers (ARs) are major drivers of precipitation across western North America, yet their role in inland, leeward watersheds of northwestern British Columbia remains poorly understood. This study develops the first watershed-scale AR climatology for British Columbia’s G aat Héeni (Silver Salmon River) Watershed, a snow-dominated basin that serves as the migration corridor for Sockeye Salmon ( Oncorhynchus nerka ) returning to G aat Áayi (Kuthai Lake). Using ERA5-Land reanalysis data (1991–2023) and the SIO-R1 AR Catalog, we quantify long-term precipitation variability and the contribution of ARs to precipitation at monthly, seasonal, and annual scales. Results from 1991 to 2023 reveal a cold, snowfall-dominated watershed with a mean annual air temperature of − 2.3 °C. Despite its proximity to the Pacific Ocean, the G aat Héeni Watershed remains relatively dry with the 1991–2023 mean annual precipitation totaling 491.5 mm, of which 66.4% falls as snow. Over 1991–2023, ARs contribute between 15.9% and 37.9% of the seasonal precipitation, with fall (September-November) exhibiting the largest share (37.9%). Annual AR contributions to precipitation range from 16.4% to 37.8%, with a mean of 26.4% over the study period. While Mann–Kendall trend tests show no significant changes at annual or seasonal scales, September consistently exhibits significant trends in AR contributions to precipitation across all intervals ( p = 0.044–0.049). This sub-seasonal signal points to September as a critical period of volatile AR influence on the G aat Héeni Watershed as this coincides with Sockeye Salmon spawning migrations.