The San Pedro River is the last undammed desert river in the American Southwest. Millions of songbirds migrate through the region every year to and from their wintering grounds in Central America and Mexico and their summer breeding grounds in Canada and the northern United States. For tens of thousands of years, they have traveled along the few north-south river corridors for shelter, food and water during their transit. In the past, the Rio Grande, San Pedro, Santa Cruz and Colorado formed these migratory corridors. Today only the San Pedro survives.

Nearly 45 percent of the 900 total species of birds in North America use the San Pedro at some point in their lives — and more birds use it now than ever before. In 1995, the American Bird Conservancy recognized the San Pedro as its first “globally important bird area” in the United States, dubbing it the “largest and best example of riparian woodland remaining” in the Southwest.
Of course, the San Pedro is renowned for its biodiversity beyond birds; it is also home to 180 species of butterflies, 87 mammals and 68 reptiles and amphibians. Jaguars and ocelots have been seen in the San Pedro River basin, which is also critical to the long-term survival and recovery of southwestern willow flycatcher, yellow-billed cuckoo, loach minnow, spikedace and Huachuca water umbel.

One of Arizona's, the nation's and the world's environmental crown jewels, this river was officially recognized by Congress in 1988 with the creation of the San Pedro Riparian National Conservation Area “in order to protect the riparian area and the aquatic, wildlife, archeological, paleontological, scientific, cultural, educational and recreational resources of the public lands surrounding the San Pedro River.” In 1993, LIFE magazine gave the San Pedro the title of one of “America's Last Great Places.”

But the San Pedro River is drying up. Unsustainable pumping of the groundwater that supports it has caused base flows to decline by 67 percent since the 1940s. The current population of more than 50,000 people in the upper basin is pumping thousands of acre-feet (billions of gallons) more out of the aquifer each year than are recharged by rainwater. By 2020, the deficit is projected to reach 13,000 acre-feet (4.2 billion gallons) annually. The burgeoning water deficit is caused by unsustainable population growth and a lack of effective water-conservation planning.

The population of the town of Sierra Vista has exploded in recent years, driven largely by nearby Fort Huachuca, the U.S. Army base that is the largest single water user in the valley. While it has made great strides in reducing per-capita water use on post, the Fort is also the region's biggest employer, driving growth and excessive, uncontrolled pumping off the post. Sierra Vista, Cochise County, the state of Arizona and the federal government haven't shown the political will necessary to protect the river. Unless things change soon, the San Pedro will resemble the lower reaches of the Santa Cruz, Gila, Salt and other Arizona rivers: dry, treeless and devoid of the diversity of life that once graced its waters and shores. A 2011 hydrology study by the Center shows that well-water levels are already declining near the river at the Fort's eastern border.


The Center has led efforts to protect the San Pedro and its wildlife for decades. We've won Endangered Species Act protection for many species that rely on the watershed, including the southwestern willow flycatcher, jaguar, Sonoran tiger salamander and Huachuca water umbel — while we're still working hard to protect the yellow-billed cuckoo, Gila chub and Chiricahua leopard frog. We've also earned the designation and protection of specific critical habitat areas along the river for the flycatcher, cactus-ferruginous pygmy owl, loach minnow and spikedace, as well as in the upper watershed for the spotted owl.

In June 2008, when the Bureau of Land Management failed to defend its conservation area on the lower San Pedro from Pinal County's road-building and dredge-and-fill operation, the Center and allies acted. We sued Pinal County for misusing the San Pedro by creating an unrestricted passageway across the lower river, straight through the San Pedro River conservation area southeast of Phoenix. Our lawsuit sought to revoke the county's illegal seizure of the land on which the passageway was created, halting dredge-and-fill operations and habitat destruction by off-road vehicles drawn to the passageway. In February 2010, the U.S. Army Corps of Engineers cited Pinal County for its illegal activities on the river and the Bureau of Land Management finally took up the proper defense of its conservation area.

The Center is currently working on several fronts to protect the San Pedro, including pressuring Fort Huachuca to adequately mitigate its presence both on and off the base and challenging the hydrologic basis of Arizona water law. A major victory came in 2011, when, in response to our lawsuit, a federal judge rejected the latest plan by the Army and U.S. Fish and Wildlife Service aimed at preventing damage to the San Pedro from groundwater pumping for Fort Huachuca. The judge described the plan as “legally flawed” and said it failed to protect the river or properly analyze groundwater pumping's effect on the ecosystem's imperiled species. An earlier key step forward in protecting the San Pedro came with the repeal of a legislative rider to the 2003 Defense Authorization Bill exempting Fort Huachuca from key protective provisions of the Endangered Species Act.

In the spring 2007 session, the Arizona state legislature authorized the creation of a special water district for the Sierra Vista subwatershed. Although local political realities may preclude much progress on properly limiting San Pedro-area groundwater pumping, the Center will be pushing for the strongest regulation possible. Ultimately, if the San Pedro is to be saved, it will be necessary to change the way Arizona water law treats groundwater pumping near all sensitive riparian areas. Along those lines, the Center is exploring the potential for a statewide ballot measure that would protect rivers like the San Pedro from depletion through excessive groundwater pumping.


San Pedro River photo © Robin Silver