Arizona River Runs Dry: A Sign of Deeper Crisis

For the second time in 122 years, a key gauge measuring the San Pedro River's streamflow near Sierra Vista has gone dry, raising alarms for one of the Southwest's last free-flowing rivers. The U.S. Geological Survey's Charleston gauge recorded zero flow for over two weeks, with a subsequent monsoon storm temporarily restoring surface flow. Conservationists emphasize that this is not equivalent to the river's essential baseflow, which is sustained by underground aquifers and is the most sensitive indicator of a river's health.

Multiple factors strain the San Pedro's water supply, including unusual climatic conditions and, significantly, extensive groundwater pumping. Both Sierra Vista and Fort Huachuca, a large military base, draw water from the underground aquifer. Environmentalists warn that this consistent pumping is depleting the bedrock reservoirs crucial for sustaining the Upper San Pedro, particularly during dry periods and droughts.

Decades ago, the U.S. Army Corps of Engineers warned of groundwater overdrawing in the region, leading to the San Pedro Riparian National Conservation Area's designation. Despite these efforts, the river's annual flow at the Charleston gauge has declined by 50% over the last century. Reports from 1970, 2005, and 2016 have consistently highlighted declining water levels and the potential impact of pumping on the river's baseflow.

In 2022, the San Pedro River was recognized as one of America's 10 most endangered rivers due to overpumping. This river is a vital oasis, supporting unique riparian habitats and millions of migratory birds annually. Without intervention, its fate could mirror other desert rivers that have dried up due to excessive groundwater extraction, underscoring the urgent need to address pumping practices.