Mesa, Arizona is home to more than half a million people, making it the third-largest city in the state and larger than many cities that get far more water-quality attention. Its drinking water comes from a mix of sources — the Salt River, the Verde River, the Central Arizona Project canal, and groundwater — and every one of those sources faces pressure.
Drought, population growth, and the emergence of PFAS as a regulated contaminant are converging on a city that was built in the desert and has to manage its water with precision.
Where Mesa’s Water Comes From
Mesa’s water supply is more diversified than many Arizona cities, which is both a strength and a complexity:
- Salt River Project (SRP) surface water — drawn from the Salt and Verde rivers via a system of reservoirs (Roosevelt Lake, Saguaro Lake, and others). This is historically the backbone of the East Valley’s supply.
- Central Arizona Project (CAP) water — Colorado River water pumped hundreds of miles uphill to central Arizona. Mesa receives CAP allocations that supplement its SRP supplies.
- Groundwater — pumped from the East Salt River Valley sub-basin. Arizona’s 1980 Groundwater Management Act limits groundwater pumping, but it remains part of the supply mix.
- Reclaimed water — treated wastewater used for irrigation, industrial purposes, and aquifer recharge. Not directly used for drinking, but it extends the overall water budget.
This diversity provides resilience, but it also means Mesa’s water quality profile shifts depending on which source is dominant at any given time. Colorado River water, for instance, has different mineral content and contaminant profiles than local surface water.
The Drought Factor
Arizona’s water future is inseparable from the Colorado River crisis. Lake Mead, the primary reservoir for CAP water, has dropped to historic lows in recent years. Federal shortage declarations have triggered cuts to Arizona’s Colorado River allocation — and those cuts disproportionately affect CAP water, which has lower priority than some other users.
Mesa’s SRP water from the Salt and Verde rivers provides a buffer, but those systems aren’t immune to drought either. Snowpack in the mountains that feed those rivers has been below average in many recent years.
What does drought mean for water quality? As reservoir levels drop, the concentration of dissolved minerals, total dissolved solids (TDS), and certain contaminants can increase. Lower water volumes in rivers and reservoirs mean less dilution of whatever’s in the water.
Mesa’s water treatment plants handle these fluctuations, but the trend line matters. A city that expects to keep growing needs both sufficient quantity and manageable quality from its sources.
PFAS: The Emerging Challenge
PFAS contamination has been detected in water sources across the Phoenix metropolitan area, and Mesa is no exception. The primary PFAS sources in the region include:
- Military installations — Luke Air Force Base (west of Mesa) and other Department of Defense sites that used AFFF firefighting foam
- Industrial facilities — semiconductor manufacturing and other industries that used PFAS-containing chemicals
- Wastewater reclamation — PFAS passes through conventional wastewater treatment and can enter the water cycle through reuse and aquifer recharge
The EPA’s 2024 PFAS drinking water standards set maximum contaminant levels of 4 parts per trillion for PFOA and PFOS. Arizona has been monitoring for PFAS in public water systems, and some detections have been reported in the greater Phoenix area.
Mesa’s water utility has been proactive about PFAS monitoring and has begun evaluating treatment options for affected sources. The city’s multiple source waters give it some flexibility — if one source shows elevated PFAS, the blend can be adjusted while treatment solutions are implemented.
What’s in Mesa’s Water
Based on Mesa’s consumer confidence reports and EPA ECHO data, the city’s water generally meets all federal standards. Some parameters worth noting:
Total dissolved solids (TDS) tend to run higher than national averages, which is typical for the desert Southwest. TDS isn’t a health concern at Mesa’s levels, but it affects taste and can leave mineral deposits on fixtures.
Hardness is high — again, typical for the region. Mesa’s water often exceeds 200 mg/L as calcium carbonate, which is considered “very hard.” This is why water softeners are so common in Arizona homes.
Disinfection byproducts (trihalomethanes and haloacetic acids) are present at levels within regulatory limits. These form when chlorine used for disinfection reacts with organic matter in the source water.
Chromium-6 (hexavalent chromium) has been detected at levels above California’s public health goal but below the federal MCL. There is no separate federal standard for chromium-6; it falls under the total chromium standard of 100 ppb. Health advocates have pushed for a lower, specific standard.
Infrastructure and Growth
Mesa has been one of the fastest-growing cities in the United States for the past decade. That growth puts pressure on water infrastructure in two ways: the system needs to serve more people, and new development needs to be connected to treatment and distribution networks.
The city has invested significantly in water infrastructure, including upgrades to its treatment plants and expansion of its reclaimed water system. Mesa’s Southeast Water Reclamation Plant and Greenfield Water Reclamation Plant are part of the city’s strategy to stretch its potable water supplies by using reclaimed water for non-potable purposes.
But growth also means more impervious surface, more stormwater runoff carrying contaminants into washes and canals, and more demand during the hottest months when supply is already stressed.
What Residents Can Do
Mesa’s water is treated and regulated, and it meets federal standards. For residents who want additional protection or who are bothered by taste and hardness:
A whole-house water softener addresses the hardness issue, which is the most common complaint from Arizona residents. Ion-exchange softeners remove calcium and magnesium, reducing scale buildup and improving soap performance.
A reverse osmosis system under the kitchen sink handles TDS, chromium-6, PFAS (if present), and most other dissolved contaminants. For a desert city with high-TDS water, RO is probably the most impactful single upgrade.
A carbon filter (either standalone or as part of an RO system) improves taste by removing chlorine and chloramine residuals and reduces disinfection byproducts.
If you’re on a private well in the Mesa area, regular testing is essential. Groundwater quality varies significantly across the East Valley, and wells near agricultural areas, former industrial sites, or military installations may have elevated contaminant levels.
If you’re concerned about your water quality, a certified water treatment professional can test your water and recommend solutions that match Mesa’s specific water chemistry.
Looking Ahead
Mesa’s water challenges aren’t crisis-level today — the city has made smart investments in diversification and treatment. But the trajectory matters. Colorado River allocations are shrinking. The population is growing. PFAS regulations are tightening. And the climate is getting hotter and drier.
The cities that manage this transition well will be the ones that invested early in treatment technology, water reuse, and conservation. Mesa has a head start on most. But the margin for error in the desert is thin, and the next decade will test every assumption about water supply in the Sun Belt.
Sources: Mesa Water Consumer Confidence Reports, EPA ECHO database, Central Arizona Project allocation data, Arizona Department of Environmental Quality, Salt River Project hydrology reports.