The primary source of water for vegetation in the Great Basin is snowmelt that flows from the surrounding mountain ranges.

Due to the region's arid and semi-arid climate, the Great Basin does not receive consistent rainfall throughout the year. Instead, the snow that accumulates on the mountain ranges surrounding the basin melts during the warmer months and provides a crucial water source. This snowmelt is essential for the growth of vegetation, especially in the more elevated areas, where it is stored in rivers and lakes before eventually being absorbed into the ground. Groundwater is another significant source, but snowmelt plays the dominant role in supporting plant life in the region.