The Santa Cruz River is a natural treasure for three nations: United States, Tohono O’odham, and Mexico. The river is nationally unique in that it originates in the in the San Rafael Valley of southern Arizona, crosses south into Mexico, then turns north to re-enter the U.S. east of Nogales. It continues its northward flow, crossing about a 10-mile stretch of the San Xavier District of the Tohono O’odham Nation, until it bends north-northwest to merge with the Gila River west of Phoenix.

Until the mid 1900s, the Santa Cruz River flowed year-round, though surface flow was intermittent in some stretches. Since then, its surface flow has dramatically diminished.

Fortunately, its watershed contains 90 miles of perennial streams and rivers that support riparian habitats—ribbons of life along shoreline communities with slow or non-flowing waters that are both beautiful and integral to life in the desert—like cienegas which are riparian marshes and havens for vegetation and wildlife.