With the exception of water provided by snow and rain, the majority of water for wildlife and most humans over the vast expanse of the desert southwest comes from groundwater, seeps, springs, and tinajas. Seeps emit water from underground that does not always reach the surface, springs are reliable perennial sources of water where groundwater reaches Earth's surface, and tinajas are surface waters in bedrock depressions. Tinajas are fed by springs and/or precipitation. Seep, spring, and tinaja ecosystems are small, relatively rare “biodiversity hot spots” in arid lands because they support a substantial number of aquatic, riparian, and terrestrial species. Many of these plants and animals depend on the aquatic ecosystem and are unique to that location.
Understanding patterns in the amount and quality of water in seeps, springs, and tinajas will help us to gauge the overall status of water resources in our parks. These waters are important to park managers because they are among the most important and limited habitats for focal and threatened plant and animal species. In some cases, identifying the condition of seeps and springs is important for human health and safety. Knowing whether surface water is available at a given site is important to park visitors planning trips into the backcountry.