The Sonoran Desert relies heavily on underground rivers and aquifers for its water sources.

In the Sonoran Desert, water is a precious and scarce resource, but it is primarily supplied by underground rivers and aquifers. These underground water reserves, known as "fossil water," are often replenished only over millennia and are crucial for supporting the desert's ecosystems and human settlements. While seasonal rain during the monsoon season can provide some surface water, the majority of the desert's water supply is found underground, especially in regions near rivers like the Colorado River. This underground system is essential for sustaining desert life, agriculture, and wildlife.