The upper San Pedro River valley in Arizona is the epitome of the Wild West. Open and arid, stretching north from Mexico and lying in the shadow of the rugged Huachuca Mountains, the valley looks much the same as it did more than a century ago when miners and settlers uneasily shared the land. It is a place where the long shadows at sunset bring visitors back to a long-past time.

Cutting across that mythic landscape is the treasure of the valley, the San Pedro River, last free-flowing river in the desert Southwest. A remnant of the formerly extensive network of desert riparian ecosystems, the river has dwindled in recent decades as development moved into the valley. And now the San Pedro may be drained to feed a proposed mega-development.

The Southwestern willow flycatcher.  (USGS)

The river’s death would imperil important habitat for a wide array of species. Even in its current diminished state, the San Pedro provides a refuge from the impacts of development and climate change. The river corridor is one of the most important migratory flyways in the United States; millions of songbirds use it each year during their migrations between Central America and Canada. And two endangered species, the Huachuca water umbel and the southwestern willow flycatcher, call the San Pedro home.

The San Pedro Riparian
National Conservation Area.  (BLM)

A critical section of the riparian habitat is embraced by the San Pedro Riparian National Conservation Area, a 57,000-acre reserve managed by the U.S. Bureau of Land Management to protect and enhance this national gem. The area includes 40 miles of river and adjacent lands. Each year, the conservation area and surrounding lands attract thousands of visitors, who contribute millions of dollars to the local economy.

But the area also includes Sierra Vista, a city of nearly 50,000 at the gates of the still active Fort Huachuca. The city, the fort and other development in this arid region are dependent on groundwater, pumping what they use from an aquifer that is intimately connected to the river.

The San Pedro’s “base flows”—flows that run year-round and are not dependent on precipitation—depend largely on water from the aquifer. The volume of groundwater pumped to accommodate the growing population, lawns and golf courses now far exceeds the amount of water naturally recharging the aquifer. This deficit pumping is leading to a decline in the river’s flow that is projected to worsen in coming years. Sadly, key stretches of the upper San Pedro now stand dry for portions of the year. The river has little left to give.

Earthjustice has worked with our partners for more than a decade to sustain the San Pedro River and the rich ecosystems that flourish there. We seek to keep water in the river until a balance can be struck between the needs of the river and the local communities. Our work has focused on a series of cases challenging inappropriate groundwater depletions by Fort Huachuca. This effort improved the fort’s water management practices and bought the San Pedro some time.

Now, the Arizona Department of Water Resources has approved a massive groundwater pumping project that could be the end of the river. This decision ignores the project’s impact on birds, wildlife, and local residents and businesses that are dependent on a healthy river.

The planned groundwater pumping will feed a massive, 7,000-home new development in Sierra Vista. By the developers’ own admission, the proposed construction will consume “virtually all of the available development land” left in the city and will significantly expand the population of this critically water-short area. The developers could not proceed with the project without the state’s determination of an adequate water supply—a determination the state could only make by assuming there is no connection between groundwater and water in the river.

Incredibly, despite volumes of scientific study demonstrating that the river and the groundwater aquifer are interconnected, the state has now made that determination and the pumping may begin.

Earthjustice attorney McCrystie Adams said:

The upper San Pedro River is the lifeblood of this region. The state of Arizona continues to hold fast to the fiction that groundwater and surface water are not connected. In the meantime, the river is disappearing and the birds, wildlife, and people who depend on a living San Pedro are left high and dry.

The BLM (asserting its federal reserved water right), conservation organizations and property owners along the river—including Dr. Robin Silver—have opposed the determination and may challenge ADWR’s action in court.

Adams added:

Allowing this groundwater mining to proceed is signing the death warrant for the river. This one decision could undo many years of hard work by residents and organizations fighting to keep the San Pedro flowing.

Earthjustice is reviewing legal options with Dr. Silver.

Follow Doug on Twitter at @dpflugh_ej