Places We Protect

San Pedro River

Arizona

Water-level view of San Pedro River with trees arching overhead.
San Pedro River southeast of Phoenix © Harold E. Malde

Innovative land and water management fosters abundant life on the San Pedro River

Overview

Description

The San Pedro River's cottonwood-shaded corridor provides critical stopover habitat for millions of migrating birds each year. It is one of only two major rivers that flow north out of Mexico into the United States and is one of the last, large undammed rivers in the Southwest.

The San Pedro River basin supports an astonishing variety of life-species typical of both the Chihuahuan and Sonoran deserts, as well as those who come just that far north from the Sierra Madre in Mexico, and just that far south from the Rocky Mountains. Species such as the jaguar and black bear stalk the region’s forested mountains while the tropical Gray hawk and yellow-billed cuckoo nest along the verdant river. The basin is home to 84 species of mammals, 14 species of fish and 41 species of reptiles and amphibians, and provides a migratory flyway of hemispheric importance for neotropical birds.

Why the Conservancy is Working Here 

Like much of the arid west, human water demands continue to increase along the San Pedro River, as a prolonged “megadrought” results in reduced water supplies for both people and nature. The Conservancy has been working with water managers, scientists, and dozens of agencies and organizations to develop new approaches to water management that will meet the specific water needs of this desert river, as well as local communities.

In addition, the Lower San Pedro Basin contains one of the largest unfragmented landscapes within Arizona, second only to the Grand Canyon. The Conservancy is working to ensure that the most important corridors for wildlife movement remain intact and to improve the quality of habitats in key areas, including the Conservancy’s Muleshoe Ranch Preserve and Aravaipa Canyon Preserve. Private lands that make up part of a protected 10-mile-long wildlife corridor linking the Galiuro Mountains to the Rincon and Catalina Mountains have also been permanently protected through conservation easements.

What the Conservancy Is Doing

  • The Conservancy is working with members of the Cochise Conservation and Recharge Network (CCRN) to implement eight aquifer protection and recharge projects along 25 miles of the river to ensure adequate water supplies remain for both local communities and the San Pedro Riparian National Conservation Area. This regional water management effort is informed by the hydrologic science produced by the 21 member agencies of the Upper San Pedro Partnership since 1998. The Conservancy was a founding member, and remains an active participant, in both collaborative groups. 
  • The Conservancy has protected key tracts of land, and significant amounts of water, in both the U.S. and Mexico working with hundreds of private, agency and corporate partners over the past three decades. Some of these places, like the Ramsey Canyon Preserve near Sierra Vista, offer exceptional hiking and bird watching opportunities. Others do not offer public visitation opportunities but are instead protected as part of private lands. 
  • Since 1999, the Conservancy has recruited hundreds of volunteer “citizen scientists” to help to map the flows of the San Pedro in both the U.S. and Mexico during the hottest, driest time of year. The results of the mapping, conducted during June of each year, allow water managers to monitor flow patterns and adapt strategies to restore year-round flows, preventing further deterioration of the ecosystem. Learn more about our projects.
  • Some streams in the Lower San Pedro River watershed are so healthy they are the site of a massive fish reintroduction effort. At Muleshoe Ranch Cooperative Management Area, healthy populations of native loach minnow, desert pupfish and spike dace are thriving.
  • At the Conservancy’s Three Links Farm, a 90 percent reduction in agricultural water use over the historic water uses is helping the river: cottonwood seedlings dot the riverbed and shores, indicating that natural flows are intact and the river is doing well. Research has begun there to learn how land management practices can improve the quality of streamside mesquite forests while also ensuring adequate water supplies remain in place for a flowing river.

Access

OPEN TO THE PUBLIC

Location

Flows north from Mexico to AZ

Map with marker: The San Pedro flows north from the Mexican state of Sonora to join the Gila River in Arizona.

Highlights

84 species of mammals, including jaguar, coatimundi, bats, beaver and many rodents; more than 41 species of reptiles and amphibians, including Sonoran tiger salamander and Western barking frog; more than 100 species of breeding birds, including the imperiled yellow-billed cuckoo; and, seasonally, more than 250 species of migratory birds. Remaining native fish species include the Gila chub which is proposed for federal listing as endangered, and the longfin dace, desert sucker, roundtail chub, Sonora sucker, and speckled dace.

Size

The San Pedro River Basin sprawls across the U.S./Mexico border near Naco, Arizona and Naco, Mexico. The river runs approximately 175 miles, from its’ headwaters in the mountains of northern Sonora downstream to its confluence with the Gila River, near Winkelman, Arizona. The river basin encompasses parts of Cochise, Pima, and Pinal Counties.

Explore our work in Arizona