The San Pedro River: What Comes After Quantification? 

By Katherine Altaffer. 

A Brief History  

In Southern Arizona, the San Pedro River snakes its way from Mexico through Southern Arizona, sustaining life for endangered species and providing a lifeline for migratory birds and wildlife. It is the last free flowing river in the American Southwest. Yet, as the City of Sierra Vista expands, the delicate balance that keeps the San Pedro alive is under strain. Decades of urging from conservationists echo along its banks, arguing that unchecked water extraction threatens the river. Despite the conservation area’s legal right to the water, the San Pedro’s protections remain unenforced: a right on paper, but not in practice. Development in the nearby city continues as the river dwindles. How does one preserve a river so vital to life, yet so vulnerable to the thirst of a growing community?

In 1988, Congress created the San Pedro National Conservation Area (“SPRNCA”) and charged the Bureau of Land Management (“BLM”) with overseeing and protecting the area. The purpose of the national conservation area was conserving, protecting, and enhancing the riparian area and the aquatic, wildlife, archeological, paleontological, scientific, cultural, educational, and recreational resources of the conservation area. In other words, there must be enough water in the river to support the nature and wildlife in the San Pedro region that the conservation area was established to protect. 

Over time, the amount of water in the river has decreased, even becoming ephemeral in some areas, meaning that it flows only in response to large precipitation events. Much of this decrease is due to groundwater pumping in the basin. Climate change has exacerbated the issue. There are more than 8,000 wells registered in the San Pedro watershed and a large number of them are located near the river. Pumping from wells has lowered the water table in the aquifer so much that the amount of water available is reduced for all wells in the area.  

The City of Sierra Vista is located very close to SPRNCA, near the San Pedro River in Southern Arizona. It is a city of over 40,000 people and shares the river with other users, including Fort Huachuca and SPRNCA, both of which have federally reserved water rights. Although outside of an Active Management Area (“AMA”)—Arizona’s groundwater law that establishes standards for developers for their groundwater use in specific areas—Sierra Vista requires proof of adequate water supply and a demonstration of 100 years of adequate water supply.   

Today’s Landscape

Conservation groups have argued for decades that excessive water extraction is threatening Southern Arizona’s San Pedro River. The Center for Biological Diversity suffered a great loss in 2008 when it sued the Arizona Department of Water Resources (“ADWR”) for approving the Pueblo Del Sol Water Company’s application for development. The Arizona Supreme Court cleared the way for the development in Silver v. Pueblo Del Sol Water Co., holding that because SPRNCA had no quantified water right, ADWR was not required to consider this in its approval of applications. 

In August 2023, Judge Brain of the Maricopa County Superior Court quantified the amount of water sufficient to fulfill the purpose of SPRNCA. Although this quantification creates a water right for now, experts believe the decision will likely be appealed. The order could be challenged by people with senior water rights, who have been using the water since before the conservation area was established. The U.S. Army’s Fort Huachuca, for example, was established in 1877 and is one of the largest water users on the upper San Pedro River. It could argue its water rights are senior to those of the conservation area.

Users who started pumping water after the 1988 declaration of the conservation area have less priority, but it is still unclear how and by whom the federal water rights could be enforced. ADWR issued about 2,400 well permits near SPRNCA and issued 66 certificates of a 100-year adequate water supply to public water systems. It is unclear whether Judge Brain’s water rights adjudication would translate into any water use restrictions even for junior users. However, in 2021, the City of Sierra Vista, Cochise County, the BLM, and Fort Huachuca signed a memorandum of understanding establishing shared goals to balance the water needs of the conservation area and the nearby communities. 

With both the quantification and the memorandum in place, developers are likely to have a difficult time proving there is enough water to build in the San Pedro Basin. Castle and Crooke Arizona, the company that owns Pueblo Del Sol Water Co., backed out of its plan to develop about 7,000 homes in Sierra Vista after Judge Brain’s ruling. Because this came after ADWR approved the Pueblo Del Sol Water Company’s application and after the Arizona Supreme Court cleared the way for the development in Silver v. Pueblo Del Sol Water Co., developers may be scared off by the threat of a water use restriction or impending lawsuits.  

What Comes Next

Actual enforcement of the quantification is more unclear. Water levels are already below court-ordered levels at most monitoring gauges. Because there are thousands of wells throughout the basin, it is hard to pinpoint one offender. The culprit could be 1,000 single family homeowners and their private wells, it could be municipalities, it could be Fort Huachuca, or some combination. There is really no way to know for sure who is responsible for depleting the river below the adjudicated standard.

On June 6th, 2024, the Center for Biological Diversity and San Pedro Alliance filed a lawsuit against the Hobbs administration alleging that the ADWR failed in its duty to review whether it is necessary to designate active groundwater management in the upper San Pedro River. This came after Hobbs’s third denied request to declare an Active Management Area in the Upper San Pedro River basin, a designation that would require more stringent groundwater standards. If the plaintiffs win, the Center could, in theory, ask the court to re-examine all the 100-year water adequacy certificates issued by the ADWR in the Sierra Vista area after 1988, based on Judge Brain’s quantification. 

It is unlikely that an already-approved development could effectively be taken to court because it is difficult to hold one party responsible and impossible to hold everyone responsible. Judge Brain’s quantification did not adjudicate specific numbers for individuals’ water use, only the amount of water that must remain in the river. An objection to the quantification will likely send the case to the Arizona Court of Appeals. 

The ultimate fight over the river’s water rights will eventually occur in the general adjudication over the entire Gila River Basin, but this has already been ongoing for almost fifty years. With the thousands of adjudications to go, it is unlikely that this will be resolved soon. Until it is resolved, the ruling might scare off already-approved new development, but will not prohibit it. Robin Silver, a cofounder of the Center for Biological Diversity, urges that our “[t]ime to save the San Pedro River is running short” as the government continues to favor real estate development over the health of our last free-flowing river and all that depend on it.