This study explores how snowmelt and rainfall supply water to plants and groundwater in a high-elevation mountain grassland. Using field data and model simulations, we tracked how snowmelt and summer rain move through the soil. Snowmelt mainly supplies deep drainage, while rain mainly feeds plants. Nevertheless, during a very dry year, snowmelt contributed more than usual to plant water use. These results show how reduced snowfalls and droughts may affect the mountain water cycle.