McAllen draws its drinking water from one of the most overallocated rivers in the Western Hemisphere — and just miles away, thousands of Texans in colonias still don’t have reliable clean water. The water story in South Texas is unlike anywhere else in the country.
Where McAllen Gets Its Water
The McAllen Public Utility supplies drinking water to roughly 150,000 residents in the city and surrounding areas. The primary source is the Rio Grande, accessed through a system of irrigation canals and reservoirs managed by Hidalgo County Irrigation District No. 1.
The water undergoes conventional treatment before distribution. But the Rio Grande itself presents unique challenges as a source: it’s shared between two nations, heavily drawn for agriculture, affected by upstream discharges from both sides of the border, and increasingly stressed by drought.
During severe drought years, the Rio Grande’s flow drops to a trickle in some stretches. Mexico’s treaty obligations to deliver water to the U.S. have been a source of diplomatic tension for decades, and water availability is never guaranteed.
Agricultural Runoff: The Constant Pressure
The Rio Grande Valley is one of America’s most productive agricultural regions. Citrus, vegetables, sugarcane, and cotton are grown across hundreds of thousands of acres — all irrigated with Rio Grande water. That irrigation returns water to the river and its tributaries carrying:
- Pesticides and herbicides from crop production
- Nitrates and phosphates from fertilizer application
- Sediment from field erosion
- Salinity — dissolved salts concentrate as water is diverted, used, and returned
The Texas Commission on Environmental Quality (TCEQ) has listed segments of the Rio Grande and its tributaries as impaired for various pollutants, including bacteria, dissolved solids, and nutrients. The Arroyo Colorado, a major drainage channel in the McAllen area, has been particularly impaired. [NEEDS VERIFICATION: current 303(d) listing status for Arroyo Colorado and nearby Rio Grande segments]
For drinking water treatment, these pollutants create extra work. Higher levels of organic matter and nutrients in source water can lead to increased disinfection byproduct formation during chlorination.
The Colonias: America’s Water Access Crisis
Within a short drive of McAllen, an estimated 400,000 or more Texans live in colonias — unincorporated settlements, many along the border, that developed without adequate infrastructure. [NEEDS VERIFICATION: current population estimate for Texas colonias] Some colonias lack running water entirely. Others have contaminated wells or unreliable connections to substandard water systems.
The colonia issue is one of the most significant environmental justice problems in the United States. Many residents rely on hauled water, shared wells of questionable quality, or connections to small systems that struggle to maintain treatment and distribution standards.
The Texas Water Development Board’s Economically Distressed Areas Program (EDAP) has funded water and wastewater infrastructure in colonias for decades, but the need far outstrips the investment. Hidalgo County, where McAllen is located, has among the highest concentrations of colonias in the state.
For residents of these communities, the water quality concerns are more basic than PFAS or disinfection byproducts — it’s about having access to treated water at all.
Fluoride: A South Texas Issue
Natural fluoride levels in groundwater across South Texas tend to run higher than in other parts of the state. While McAllen’s treated surface water is fluoridated at controlled levels, private wells in the region may contain naturally elevated fluoride.
Excessive fluoride exposure — above the EPA’s maximum contaminant level of 4 mg/L — can cause skeletal fluorosis and dental damage. The secondary standard of 2 mg/L is set to prevent cosmetic dental effects. Some wells in the Rio Grande Valley have been documented with fluoride above these thresholds. [NEEDS VERIFICATION: specific fluoride levels in Hidalgo County private wells]
If you’re on a private well in South Texas, fluoride testing is important — it’s not something you can taste or smell at the levels that matter.
What the Data Shows
McAllen’s annual Consumer Confidence Reports generally show compliance with federal drinking water standards. The city’s treatment plant handles the challenges of Rio Grande source water effectively most of the time. However, several factors bear watching:
- Total dissolved solids (TDS) — the Rio Grande carries high mineral content, and TDS levels in treated water can be elevated, affecting taste
- Disinfection byproducts — the high organic load in source water can drive TTHM and HAA5 formation
- Nitrates — agricultural runoff keeps nitrate levels in source water elevated, though treatment typically brings them below the MCL of 10 mg/L
- Haloacetic acids — have been detected at levels that, while below the MCL, warrant attention
EPA’s ECHO database shows the McAllen system has maintained general compliance, but the source water challenges mean the treatment plant has to work harder than systems drawing from cleaner sources. [NEEDS VERIFICATION: any recent SDWA violations for McAllen Public Utility]
Drought and Water Security
Water quantity is as much a concern as water quality in the Rio Grande Valley. The region experienced severe drought conditions in recent years, with reservoir levels dropping to alarming lows. Falcon and Amistad reservoirs — the two international reservoirs that store Rio Grande water for the lower valley — have seen dramatic fluctuations.
When water levels drop, contaminant concentrations increase in the remaining water. Drought also increases competition between agricultural, municipal, and environmental water needs. McAllen and other valley cities have invested in water conservation programs, but the fundamental supply constraint isn’t going away.
Climate projections suggest the Rio Grande basin will face increasing drought stress in coming decades, making water security an existential issue for the region.
What McAllen Area Residents Should Do
Get your water tested. Whether you’re on city water or a private well, baseline testing gives you a clear picture. For city water, request the latest Consumer Confidence Report from McAllen Public Utility. For wells, test for bacteria, nitrates, fluoride, TDS, and pesticides.
Know your source. If you’re on city water, you’re getting treated Rio Grande water. If you’re on a well, understand your aquifer and what’s happening upstream or upgradient.
Consider a point-of-use filter. A reverse osmosis system can address TDS, nitrates, fluoride, and disinfection byproducts — all relevant concerns in this region. Activated carbon filters handle taste, chlorine, and some organic compounds.
Stay aware of drought conditions. Water restrictions aren’t just about conservation — they can signal source water quality changes too.
If you’re in a colonia without reliable water access, contact the Hidalgo County colonia services program or the Texas Water Development Board about infrastructure assistance programs.
If you’re concerned about your water quality, a certified water treatment professional can test your water and advise on solutions.