Colorado has stricter environmental regulations and a PFAS action plan that includes state-funded testing beyond federal requirements. Arizona faces naturally occurring arsenic in groundwater, heavy Colorado River dependence, and limited state-level water quality enhancements. Colorado provides better regulatory protection; Arizona's geology creates unique contamination risks.
Colorado and Arizona both depend on the Colorado River but face very different water quality challenges. Colorado's contamination story centers on military PFAS and mining legacy. Arizona battles naturally occurring arsenic, drought-driven concentration of contaminants, and infrastructure strain from some of the fastest population growth in the country. Here's what the data shows.
This article contains affiliate links. If you buy through them, we may earn a small commission at no extra cost to you.
Colorado's Department of Public Health and Environment (CDPHE) regulates about 930 community water systems serving 5 million residents. The state has been proactive on PFAS, launching a statewide PFAS testing initiative in 2022 and developing a PFAS action plan that goes beyond federal requirements. Arizona's Department of Environmental Quality (ADEQ) oversees roughly 790 community systems for 6.5 million people, following the federal framework without major state-level additions.
Check your water quality by zip code to see the specific test results for your water system.
Colorado's PFAS contamination is concentrated around military installations. Peterson Space Force Base and Schriever Space Force Base near Colorado Springs have confirmed PFAS in groundwater. Buckley Space Force Base near Denver and the former Lowry Air Force Base site also show contamination. The Colorado Springs PFAS situation affected the Widefield Water and Sanitation District, where PFOS levels in some wells exceeded 70 ppt – seventeen times the federal limit.
Arizona's PFAS hot spots include Luke Air Force Base near Phoenix, Davis-Monthan Air Force Base in Tucson, and the former Williams Air Force Base site in Mesa. A 2024 ADEQ sampling found PFAS in groundwater at 8 of 12 tested military-adjacent sites, according to the agency's annual water quality report.
Both states depend on the Colorado River, but Arizona's dependence is existential. The Central Arizona Project canal delivers Colorado River water 336 miles across the desert to Phoenix and Tucson, serving over 5 million people. As the river's flow declines due to drought and overallocation, Arizona's water supply security is among the most precarious in the nation.
Colorado sits upstream on the Colorado River and also draws from the South Platte and Arkansas river systems. Snowmelt from the Rocky Mountains provides relatively clean source water, though mining legacy contamination in mountain communities adds heavy metals like cadmium, zinc, and arsenic to some local water supplies.
Arizona faces a unique contaminant that Colorado largely doesn't: naturally occurring arsenic. The desert geology releases arsenic into groundwater, and the EPA's MCL of 10 ppb is frequently exceeded in small Arizona systems. According to ADEQ data, over 50 Arizona water systems have reported arsenic detections above 10 ppb in the past five years. Arsenic is a known carcinogen linked to bladder, lung, and skin cancers.
Colorado is the more proactive regulator. The state launched a PFAS action plan in 2022, funded statewide testing beyond UCMR5 requirements, and is developing state-specific MCLs expected to take effect in 2026. Colorado also has stricter monitoring requirements for small systems and has been more aggressive on mining-related contamination cleanup under state superfund authority.
Arizona follows the federal framework without state-level enhancements for PFAS or most other emerging contaminants. The state's regulatory focus has been on water quantity – managing drought and Colorado River allocations – rather than water quality. While ADEQ conducts compliance monitoring, it has not proposed state-level PFAS standards or expanded testing requirements beyond federal minimums.
Colorado has the regulatory edge and cleaner source water. Mountain snowmelt is about as good a starting point as you get for water treatment. The state's proactive approach to PFAS – testing more, regulating earlier, funding cleanup – gives residents better protection and more information.
Arizona's challenges are harder to regulate away. Naturally occurring arsenic isn't a failure of regulation – it's geology. Colorado River water quality degrades as it travels downstream, picking up agricultural runoff and dissolved minerals. And Arizona's explosive growth puts strain on treatment infrastructure that wasn't built for current demand.
The verdict: Colorado provides better regulatory protection and starts with cleaner source water. Arizona faces structural challenges – arsenic, drought, and distance from water sources – that regulations alone can't fully address.
Check your water quality by zip code to see contamination data for your system. Arizona residents should specifically look for arsenic levels in addition to PFAS. Colorado Springs-area residents should check PFAS results given the military base contamination history.
If you find elevated contaminants, the AquaTru reverse osmosis system removes PFAS, lead, and arsenic. The Brita Elite handles lead and some PFAS but is not rated for arsenic. Arizona residents with arsenic concerns should use RO. Full guide: water filters.
Detailed reports: get a water quality PDF report. State pages: Colorado and Arizona.
Is Colorado or Arizona water safer to drink? Colorado has stricter regulations, cleaner source water from mountain snowmelt, and a proactive PFAS testing program. Arizona faces naturally occurring arsenic in groundwater and heavier dependence on Colorado River water. Colorado provides better regulatory protection overall.
Does Arizona water have arsenic in it? Yes. Arizona's desert geology naturally releases arsenic into groundwater. Over 50 Arizona water systems have reported arsenic levels above the EPA's MCL of 10 ppb in recent years. Arsenic is a known carcinogen – reverse osmosis filtration removes it effectively.
Is Colorado Springs water contaminated with PFAS? The Widefield Water and Sanitation District near Colorado Springs has documented PFAS contamination from Peterson and Schriever Space Force Bases. Some wells showed PFOS levels exceeding 70 ppt – seventeen times the federal limit. The state and DoD are funding remediation.
Is Colorado River water safe to drink? Colorado River water is treated before distribution, but its quality degrades as it flows downstream from Colorado through Arizona. By the time it reaches Phoenix and Tucson via the Central Arizona Project, it contains higher levels of dissolved minerals and agricultural runoff than at its mountain source.
What filter removes arsenic from Arizona water? Reverse osmosis systems remove arsenic effectively – the AquaTru countertop RO removes up to 99% of arsenic along with PFAS and lead. Standard carbon filters like the Brita Elite do not remove arsenic. Arizona residents with arsenic concerns should use RO specifically.