El Paso, Texas is the largest city in the Chihuahuan Desert, and it has spent the last three decades reinventing how a desert city manages water. The results are genuinely impressive — and the challenges are still enormous.
El Paso Water (the municipal utility) serves about 690,000 people using a mix of Rio Grande surface water, Hueco Bolson groundwater, Mesilla Bolson groundwater, and reclaimed water. The city also operates the largest inland desalination plant in the Western Hemisphere. It’s a complex system built out of necessity.
The Hueco Bolson: Running on Empty
The Hueco Bolson is the aquifer that sits beneath El Paso and Ciudad Juárez, Mexico. For most of the 20th century, both cities pumped it aggressively. By the 1990s, water level declines were alarming — some areas dropped more than 150 feet. At the rate of extraction, the freshwater portion of the aquifer was projected to be exhausted by 2025.
That projection forced El Paso to act. The city dramatically reduced its groundwater pumping, invested in reclaimed water for non-potable uses (parks, golf courses, industrial), and built the Kay Bailey Hutchison Desalination Plant in 2007 to treat brackish water from the deeper, saltier portions of the Hueco Bolson.
The result: El Paso pulled back from the brink. Groundwater levels have stabilized in some areas and even recovered slightly. But the freshwater zone is still severely depleted, and the city remains dependent on the Hueco Bolson as a supplemental source during years when Rio Grande allocations are short.
Arsenic and Brackish Water
The Hueco Bolson contains naturally elevated arsenic in many areas, particularly in the brackish zones. The desalination plant was designed partly to address this — reverse osmosis removes arsenic along with dissolved salts.
Some older wells that tap shallower freshwater zones have also shown arsenic levels near the EPA MCL of 10 ppb. El Paso Water manages this through blending and treatment, but the natural geology means arsenic will always be part of the water quality conversation here.
The Rio Grande: Shared and Stressed
El Paso’s surface water comes from the Rio Grande, allocated through a complex web of interstate compacts (the Rio Grande Compact) and international treaties (the 1906 Convention with Mexico). The river is managed by the U.S. Bureau of Reclamation through Elephant Butte Reservoir in New Mexico.
In wet years, El Paso gets a full allocation. In drought years — which have dominated the 2020s — allocations shrink dramatically. The Rio Grande has run dry through El Paso during some recent summers, something that would have been unthinkable a generation ago.
Water quality in the Rio Grande varies. Agricultural return flows from southern New Mexico add salts, nutrients, and pesticide residues. Urban runoff from both sides of the border contributes bacteria and contaminants. El Paso’s treatment plants handle these, but the raw water quality fluctuation is a challenge.
Cross-Border Contamination
El Paso and Ciudad Juárez share the same aquifer, the same river, and the same airshed. What happens on one side of the border affects the other. Juárez’s wastewater treatment capacity has historically lagged behind its population growth, and untreated or partially treated wastewater has contaminated portions of the Rio Grande and Hueco Bolson.
The Border Environment Cooperation Commission and the North American Development Bank have funded improvements to Juárez’s wastewater infrastructure, but the scale of the challenge is immense. A metropolitan area of over 2 million people straddling an international border in a desert is inherently complicated.
Advanced Water Reuse
El Paso is planning to become one of the first U.S. cities to implement direct potable reuse — treating wastewater to drinking water standards and putting it back into the supply. The Advanced Water Purification Facility, planned as an expansion of the existing reclamation system, would use reverse osmosis and advanced oxidation to produce water that meets or exceeds all drinking water standards.
This is the future of water in the arid West. El Paso is leading the way, and the technology works. The challenge is public acceptance and regulatory frameworks that haven’t caught up with the engineering.
What Residents Can Do
- Conserve. El Paso has cut per-capita water use by over 30% since the 1990s. Keep going — every gallon saved extends the supply.
- Know your source. El Paso Water’s blend changes seasonally. Taste and hardness fluctuations are normal.
- Filter if concerned. Reverse osmosis handles arsenic, salts, and most contaminants. It’s the go-to for El Paso’s water chemistry.
- Private well owners in El Paso County: Test for arsenic, TDS, nitrates, and bacteria. Brackish water quality varies enormously by depth and location.
- Support reuse. Direct potable reuse is safe, proven, and necessary for the desert Southwest. Understanding the technology helps build community support.
If you’re concerned about your water quality, a certified water treatment professional can test your water and recommend the right treatment for your situation.
See also our coverage of Albuquerque water quality and Tucson water quality.
Sources: El Paso Water, Texas CEQ, EPA SDWIS, USGS, International Boundary and Water Commission