A new report from the Center for Biological Diversity shows decades of groundwater pumping at Fort Huachuca, in southern Arizona, has depleted the aquifer to the point that it has reached the San Pedro River.
The San Pedro River travels north into Arizona from across the border in Mexico. It’s the last free-flowing river in the American Southwest.
It’s fed by the same aquifer that supplies Fort Huachuca and the city of Sierra Vista nearby. The Center for Biological Diversity report, published this month, uses 20 years of data from well flow and finds that since the 1950s, the military base has pumped 400,000 acre feet of water from the aquifer that has not yet been replenished, creating a deficit.
The report builds on an Army Corps of Engineers memo from 2005 that found pumping could result in a loss of the river’s flow.
“Undoubtedly now, the effects have reached the river. We now see a significant diminishment of the base flow of the river itself adjoining the base,” said report author and center co-founder, Robin Silver.
The base flow is the amount of water that flows out of the aquifer and feeds the riverbed during the driest times of the year. Silver says if the water table dips below the river, the river will disappear. The report concludes the only way to save the flow is to downsize Fort Huachuca.
“Fort Huachuca and its attributable population are the single largest extractor of groundwater [in the area]. They use water just like the rest of us do,” Silver said. “It's not being replaced, and now the unmitigated deficit has caught up with them to the point that it's killing the San Pedro River.”
In response to questions sent about the report, Fort Huachuca Public Affairs Officer Angela Camara said the base is engaged in conservation efforts with U.S. Fish and Wildlife Service. She declined to respond to or answer questions about the report’s assertions, saying the base was not involved in its preparation.
“We actively engage U.S. Fish & Wildlife Service to review water conservation initiatives, including effluent and recharge,” she said in an email. “One such initiative is the use of effluent to water the golf course which saves from pumping additional groundwater, and any unused effluent is recharged back into the aquifer.”
