The Santa Cruz River is the fourthmost endangered river in America, according to American Rivers’ 2024 rankings.
The river conservation nonprofit released its annual America’s Most Endangered Rivers list Tuesday to call attention to 10 of the most at-risk rivers and streams due to drought, pollution and climate change.
Nominated by the Sonoran Institute, the Santa Cruz was listed due to threats to water security and climate change. All rivers in New Mexico were ranked first on the list following a Supreme Court rollback on Clean Water Act protections.

The Sackett vs. EPA ruling left 96% of New Mexico’s streams vulnerable to pollution with potential downstream impacts to the Rio Grande, Gila, San Juan and Pecos rivers, American Rivers said.
“All water is connected. We cannot allow pollution anywhere without risk to the rivers we rely on for drinking water,” said Tom Kieran, president and CEO of American Rivers. “America’s Most Endangered Rivers is a national call to action to defend the streams and rivers on which all life depends.”

The Colorado River in the Grand Canyon was the most endangered river last year. The Colorado has made the list several times, and American Rivers has previously highlighted other Arizona rivers, including the Gila, the Verde and the San Pedro.
Climate change, weakened regulation imperil many rivers
The American Rivers report calls for protection and aims to raise awareness of the 10 rivers featured and conservation for all 3 million miles of rivers across the nation.
The list signals severe degradation to the nation’s waterways, as about 44% are too polluted for swimming or fishing according to the EPA, and freshwatermarine life is going extinct at unprecedented rates. Climate change has spurred severe floods and droughts, and new legal rulings have scaled back protections, worsening water quality, the group says.

The Clean Water Act was enacted in 1948 and implemented pollution control programs to keep waterways clean. It set wastewater standards and made it illegal to release pollutants into navigable waters without a permit.

The 10 most endangered rivers
1. Rivers of New Mexico 2. Big Sunflower and Yazoo Rivers (Mississippi)
3. Duck River (Tennessee) 

4. Santa Cruz River (Arizona) 

5. Little Pee Dee River (North Carolina, South Carolina)
6. Farmington River (Connecticut, Massachusetts)
7. Trinity River (California) 

8. Kobuk River (Alaska) 

9. Tijuana River (California, Mexico) 

10 . Blackwater River (West Virginia, Virginia)

In 2023, the EPA amended the definition of “Waters of the United States” based on the Sackett vs. EPA decision. It narrowed the scope of waters subject to federal jurisdiction, deeming relatively permanent or continuously flowing waterways “forming geographic features” qualify.

The new definition also states the Clean Water Act only applies to wetlands that are difficult to distinguish from waterways. To nominate waterways threatened in some way, local groups had to prove the river’s importance to people and wildlife, the severity of the threat to the river and community and identify a decision in the next 12 months the public can influence.

Santa Cruz flows with treated wastewater. The Santa Cruz has been revitalized in the last 15 years, but advocates worry climate change and water scarcity could undo years of progress. The river’s perennial flows ceased in 1913 from extreme groundwater use, and seasonal flows followed in 1940. In the following decades, partially treated wastewater was discharged into the river, worsening water quality that endangered the ecosystem and the surrounding communities.

In 2008, wastewater treatment facilities were updated and now provide about 35 miles of perennial flows. As water quality improved, native fish, wildlife and vegetation have returned to the river.
As Tucson relies on water supplies from the dwindling Colorado River, advocates fear less wastewater will be released into the Santa Cruz.
“The water is treated to a really high quality and then released into the Santa Cruz, but you need water in the first place to create the Santa Cruz,” said Luke Cole, Santa Cruz River program director for the Sonoran Institute. “That’s really what the main threat is.”
Why advocates campaign for protection

The Sonoran Institute is campaigning for an Urban National Wildlife Refuge designation to protect the Santa Cruz. If granted by the U.S. Fish and Wildlife Service, this designation would provide funding for the federal government to buy parcels of land that would be protected permanently.

National wildlife refuges must be within 25 miles of urban areas and help residents engage with nature and protect wildlife. The designation would allow the government to acquire more property in the future, provide open spaces for wildlife and provide amenities within the refuge.

“We’re seeing people using the river again, native fish, birds and wildlife are coming back,” Cole said. “All of this desert life needs the Santa Cruz River, and the recognition of it through this campaign is a great tool to help people refamiliarize themselves with this system and see the value in it.”

Beyond the potential designation, Cole hopes the Santa Cruz’s place on the endangered rivers list will raise awareness about the threats to the river, and encourage the public to advocate for its survival.
“For me, this is really a rebirth story that deserves to be told,” Cole said. “To see the recovery of the Santa Cruz River in the last 15 years is unlike anything I’ve ever seen before.”

Hayleigh Evans covers environmental issues for The Arizona Republic and azcentral. Send tips or questions to hayleigh. evans@arizonarepublic. com. ---This article was reprinted from The Arizona Republic.

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