Atmospheric rivers (ARs) can induce heavy precipitation and modulate land surface hydrological processes. Previous studies have investigated the impact of ARs on different surface water budget components, such as extreme precipitation, rain-on-snow, and extreme runoff. However, few studies have evaluated the impact of ARs on the overall surface water budget. In this study, we quantified the impact of ARs on the land surface hydrological processes across the western U.S. watersheds based on a high-resolution regional climate simulation. We analyzed the statistical behaviors of major water budget components (snowpack, soil moisture, evapotranspiration, and runoff) during AR and non-AR events, and attributed the differences to specific meteorological conditions of ARs (heavy precipitation, increased air temperature, and modified radiation reaching the ground). Our analysis indicates that during AR events, snowpack change is altered by both temperature and radiation, evapotranspiration is more dominantly controlled by temperature, and water input to the snow-soil continuum is heavily modulated by precipitation. By altering water inputs to the soil, ARs have cumulative effects on runoff generation and water availability. Last, investigation of the relationship between ARs and the seasonal distribution of water resources highlights the importance of considering ARs in water resources planning and management.