TUCSON, Ariz. – A U.S. Army base nestled at the foot of a southern Arizona mountain range is threatening a sensitive desert waterway sometimes called America’s most endangered river, two environmental groups said in a federal lawsuit Friday.
Groundwater pumping at Ft. Huachuca is lowering the water table near the San Pedro River, putting at risk habitat for almost 500 species of animals, including several endangered species and millions of birds that navigate up and down the river on their annual migrations, the Center for Biological Diversity and Maricopa Audubon Society said in the lawsuit filed in U.S. District Court in Tucson.
“It’s heartbreaking that the San Pedro and its irreplaceable wildlife are being sacrificed because the fort and local governments refuse to reduce groundwater use,” said Robin Silver, cofounder and board member of the Center for Biological Diversity. “They’re willfully killing this beautiful river.”
The lawsuit challenges a 2014 biological opinion in which the U.S. Fish and Wildlife Service, a defendant in the lawsuit along with the fort’s commander, Secretary of the Interior David Bernhardt, Secretary of Defense Mark Esper, Fish and Wildlife Director Aurelia Skipwith and three others involved in the decision, found the pumping at the fort and adjoining town of Sierra Vista, with a combined population of about 60,000, would not impact endangered species along the river.
That decision – made even though the agency knew the pumping would impact flows in the river – flies in the face of available science, especially considering the effects of climate change, the plaintiffs claim.
“Of particular relevance to this case, the changing climate has made the American Southwest both hotter and drier in recent decades, and these effects will intensify during this century,” the lawsuit claims.
The San Pedro, the last undammed free-flowing desert river in the Southwest, is an intermittent stream that starts in northern Mexico and flows north into the U.S. about 20 miles southeast of Ft. Huachuca. The flow in the river is spotty along its 170 mile length, often disappearing and reappearing seasonally or based on nearby groundwater pumping on ranches or in towns.
For 21 years, volunteers for The Nature Conservancy, which manages several preserves along the river, have been mapping San Pedro flow annually. In June 2019, volunteers found water in most portions of the river east of Ft. Huachuca, but a mostly dry river north of the fort.
Groundwater pumping risks habitat for the Huachuca water umbel, a rare plant; the northern Mexican garter snake, which feeds mainly on frogs and fish from the river; the Southwest willow flycatcher, which uses the river for nesting and for migration to Latin American winter habitat; the Western yellow-billed cuckoo; and other species, according to the plaintiffs.
The fort’s water use leaves the watershed with an annual deficit, because the surrounding desert gets just 14 inches of rain per year. A U.S. Geological Survey estimate for 2012 put the deficit at 5,000 acre-feet per year, the lawsuit says, which is enough water for about 15,000 average households.
A previously undisclosed 2010 report commissioned by the U.S. Army showed that groundwater pumping attributable to Fort Huachuca and nearby Sierra Vista was harming the river and endangered wildlife in 2003, The Center for Biological Diversity said in a news release.
The Fish and Wildlife Service failed to consider those findings in the 2014 approval of the fort’s groundwater pumping for another decade, the news release said.
“In the midst of an extinction crisis the Army and local officials are wiping out one of the country’s environmental crown jewels,” said Mark Larson, president of the Maricopa Audubon Society. “This fragile river will be lost forever if the fort doesn’t act quickly to reduce groundwater use.”
Alex Hardee, an attorney for Earthjustice, which is representing the plaintiffs, said the lawsuit is an attempt to halt the fort’s longstanding practice of relying on faulty groundwater data.
“For years the fort has evaded the Endangered Species Act by disregarding the science and relying on illusory water credits,” Hardee said. “We filed this lawsuit to put an end to this pattern and practice, and to force the U.S. Army and Fish and Wildlife Service to comply with the Endangered Species Act.”
The Fort Huachuca Public Affairs Office did not immediately respond to a call seeking comment.