San Pedro River Named Among America’s Most Endangered Rivers of 2022

Groundwater pumping, harmful development threaten endangered fish and wildlife 


Sinjin Eberle, American Rivers, (720) 373-0864

Geoffrey Nolan, Earthjustice, (202) 740-7030

Today, American Rivers named the San Pedro River one of America’s Most Endangered Rivers® of 2022, highlighting the threat that excessive groundwater pumping and harmful development pose to one of the most biodiverse ecosystems in North America and one of the last major free-flowing rivers in the desert Southwest.

Stretches of the San Pedro River that previously flowed year-round are drying up. The base flow of the river is sustained by groundwater from the regional aquifer, which keeps the river flowing during the dry season. However, groundwater levels across much of the river’s watershed are declining due to ever-increasing demands. Additionally, rollbacks to the Clean Water Act initiated during the Trump administration have removed protections for seasonal and intermittent streams, which encompass almost 94% of the San Pedro River’s waterways and provide the lifeblood that sustains the river.

“America’s Most Endangered Rivers is an urgent call to action,” said Sinjin Eberle with American Rivers. “The San Pedro is an essential water resource in this desert region. The river’s fate and our own are intertwined.”

American Rivers and its partners called on Arizona legislators to pass laws to protect groundwater supplies and urged the Biden administration to strengthen federal Clean Water Act protections.

“The San Pedro River is one of the most biodiverse ecosystems in North America, but its future is under threat due to rampant development, lack of state level protections, and lingering policies from the Trump administration,” said Earthjustice Legislative Counsel Julián Gonzalez. “In order to protect this iconic river, the Arizona legislature must quickly pass policies to protect precious groundwater supplies while the Biden administration must forcibly reject the Trump administration’s dirty water rule and issue a new rule that offers better protections for our nation’s waterways.” 

“The San Pedro River is an important life source for Arizona,” said Rep. Raúl M. Grijalva, Chair of the House Natural Resources Committee. “Its waters give life to a rich diversity of animals, plants, and other wildlife, while also being part of the increasingly limited supply of groundwater that is vital to communities and local businesses across the state. Out-of-state developers have taken advantage of the rollback of clean water protections by the previous administration and forced this precious resource to the brink. We must use this as a call to action to protect the San Pedro River and ensure that we preserve these vulnerable ecosystems now before it’s too late.”

“The San Pedro River — the last free-flowing river in the southwest, is hugely important to the entire region. We must be aggressive in strengthening clean water protections and highlighting the issue,” said Rep. Ann Kirkpatrick. “It is crucial we preserve the unique biodiversity of our riparian environment and maintain water levels in the aquifer system below ground. I commend environmental leaders and organizations both locally and nationally for recognizing this importance and working together to preserve this lifeline for current and future generations.”

“If you have ever wondered how much difference it makes to have even a trickle of water in the desert, you need look no farther than the San Pedro River,” said Sierra Club Grand Canyon Chapter Director Sandy Bahr. “This river is not one of those large raging rivers, yet it sustains a significant diversity of plants and animals, including some that are just passing through via this flyway. Sadly, this river is critically endangered as groundwater pumping in the region threatens to literally drain it of its essence. We must do everything we can to stop that and keep the San Pedro flowing.”

“It’s been distressing, even heartbreaking, to have watched the riparian area decline in just a few decades,” said Tricia Gerrodette for the San Pedro 100. “I hope the attention this brings will help provide stronger protection for this special place.”

“The San Pedro River has become the default site for mitigating ecological impacts caused by rapid development elsewhere in Arizona, and now these federal mitigation designations are being threatened due to the lack of protective measures,” said chair of the Lower San Pedro Watershed Alliance Peter Else. “We must protect the last remaining natural and intact desert river ecosystem in southern Arizona. We must think beyond the span of our brief lifetimes.”

Across Arizona — where more than 40% of the water supply comes from groundwater — residents and businesses are drilling wells deeper to reach water as they continue to dry up and the water table continues to sink. The threat to the river and water supplies will only grow with climate change, as the Southwest becomes hotter and drier.

The proposed Villages at Vigneto development in Benson, Arizona, exemplifies the groundwater threat to the San Pedro River. This residential and commercial community development would span more than 12,000 acres and would include 28,000 homes, golf courses, vineyards, resorts and commercial buildings, potentially increasing the population of the riverside town from 5,000 to as many as 75,000. Doing so could increase groundwater pumping from approximately 800 acre-feet to as much as 13,000 acre-feet per year, sucking water from aquifers that maintain the San Pedro’s stream flows.

This ongoing problem was exacerbated in 2020, when the Trump administration issued what has become known as the “Dirty Water Rule,” which cut millions of streams and wetlands out of safeguards guaranteed by the Clean Water Act by excluding them from the definition of “Waters of the U.S.” Modeling showed that nearly 94% of all wetlands and flowlines in Arizona’s Upper San Pedro watershed would lose protection under the Rule.

The San Pedro is home to many endangered and threatened species, such as the jaguar, ocelot, southwestern willow flycatcher, western yellow-billed cuckoo, lesser long-nosed bat and the rare Huachuca water umbel plant. Recognizing the importance of the San Pedro, Congress protected 40 miles of the upper San Pedro River as a National Conservation Area in 1988.

The annual America’s Most Endangered Rivers® report is a list of rivers at a crossroads, where key decisions in the coming months will determine the rivers’ fates. Over the years, the report has helped spur many successes including the removal of outdated dams, the protection of rivers with Wild and Scenic designations, and the prevention of harmful development and pollution.

The San Pedro was previously highlighted on this list in 1994, 1995, and 1999. The Colorado River tops the endangered list this year as well. Other rivers in the region listed as most endangered in recent years include the Pecos River (2021) and Gila River (2019).

American Rivers reviews nominations for America’s Most Endangered Rivers from local groups and individuals across the country, and selects rivers based on three criteria: 1) the river’s significance to people and wildlife, 2) the magnitude of the threat to the river and communities, especially in light of climate change and environmental justice, 3) a decision in the next 12 months that the public can influence.

America’s Most Endangered Rivers® of 2022

  1. Colorado River  
    • State: CO, UT, AZ, NV, CA, WY, NM, Mexico  
    • Threat: Climate change, outdated water management  
  2. Snake River  
    • State: ID, WA, OR  
    • Threat: Four federal dams  
  3. Mobile River  
    • State: AL  
    • Threat: Coal ash contamination  
  4. Maine’s Atlantic Salmon Rivers  
    • State: ME  
    • Threat: Dams  
  5. Coosa River  
    • State: TN, GA, AL  
    • Threat: Agricultural pollution  
  6. Mississippi River  
    • State: MN, WI, IL, IA, MO, KY, TN, AR, MS, LA  
    • Threat: Pollution, habitat loss  
  7. Lower Kern River  
    • State: CA  
    • Threat: Excessive water withdrawals  
  8. San Pedro River  
    • State: AZ  
    • Threat: Excessive water pumping; loss of Clean Water Act protections  
  9. Los Angeles River  
    • State: CA  
    • Threat: Development, pollution  
  10. Tar Creek  
    • State: OK  
    • Threat: Pollution

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