Well Water in Sierra Vista / Huachuca City, Arizona

Cochise County · Population ~50,000 · Aquifer: Upper San Pedro Basin Regional Aquifer

Hardness: Moderate to Hard

The Upper San Pedro Aquifer

The Upper San Pedro Basin aquifer is the sole water source for Sierra Vista, Fort Huachuca, and surrounding communities. It's also the lifeblood of the San Pedro River — an ecologically irreplaceable riparian corridor and the last major free-flowing river in the Southwest.

Regional aquifer water levels have been in steady decline since at least the mid-1990s. A USGS study documented the cone of depression centered on Sierra Vista and Fort Huachuca pumping centers — the area where concentrated pumping has pulled the water table down the most.

The general direction of groundwater flow is to the northeast toward the San Pedro River, except where pumping redirects it. When pumping exceeds natural recharge, the aquifer stops feeding the river — the river goes dry.

Fort Huachuca Contamination

Fort Huachuca, the Army installation adjacent to Sierra Vista, has two documented contamination sites:

• The South Range Landfill — contamination detected in shallow soil and leachate
• The East Range Mine Shaft — trace contaminants detected historically

Data collected to date indicates the regional aquifer has not been impacted above Aquifer Water Quality Standards near either site. Sierra Vista's drinking water wells draw from the deeper regional aquifer, which appears protected by the vertical separation.

All 26 drinking water systems in the Sierra Vista area have been in compliance since 1989. No industrial solvents or gasoline components have been detected in drinking water. But monitoring continues, because the contamination exists above the aquifer that everyone depends on.

Water Supply vs. Environmental Preservation

Sierra Vista faces a tension that few Arizona communities share: every gallon pumped from the aquifer is a gallon that doesn't reach the San Pedro River. Federal designation of the San Pedro Riparian National Conservation Area creates legal and ecological pressure to maintain river flows.

The community has implemented aggressive water conservation and recharge programs. Treated effluent is recharged to the aquifer. But population growth continues, and the balance between human water needs and river preservation remains precarious.

For private well owners, this context matters. Conservation requirements may tighten. Water availability may not grow with demand. Plan accordingly.

Testing Recommendations

Sierra Vista area well owners should test for:

• Arsenic — common in southern Arizona basin-fill aquifers
• Bacteria and nitrate — annual basics
• Hardness, TDS, fluoride, pH — baseline mineral panel
• VOCs — if near Fort Huachuca or any military/industrial facility

See our testing guide for certified labs.