Hidalgo County, Texas: drinking water report. Hidalgo County sits at the southern tip of Texas along the Mexican border, with a population of about 870,000
Hidalgo County sits at the southern tip of Texas along the Mexican border, with a population of about 870,000 – making it one of the most populous counties in the state. McAllen, Edinburg, Mission, and dozens of smaller cities and colonias draw water from the Rio Grande and from groundwater wells tapping the Gulf Coast Aquifer. The colonias – unincorporated communities often lacking basic infrastructure – face water quality challenges that are distinct from those in the county's larger cities.
The Rio Grande at this point has traveled over 1,800 miles, accumulating agricultural runoff from New Mexico and West Texas, industrial discharges, and treated wastewater from both U.S. and Mexican communities. According to the TCEQ's 2024 Rio Grande Basin monitoring report, the river consistently exceeds recommended levels for total dissolved solids, sulfate, and chloride at monitoring stations in Hidalgo County.
Some colonias in the county still rely on private wells that draw from shallow aquifer zones contaminated by inadequate septic systems. A 2023 Texas A&M ColoniaS Program assessment found that 8% of tested private wells in Hidalgo County colonias exceeded the MCL for coliform bacteria, and 12% exceeded nitrate limits. The EPA's UCMR5 data shows low-level PFAS detections in the larger municipal systems.
If you live in a colonia served by a private well, testing for bacteria and nitrate is a safety baseline that should happen at least annually. Municipal systems in McAllen and Edinburg treat for these contaminants, but the quality of your water depends entirely on which system – or which well – serves your home.
Check your water for the latest monitoring data in your area. For bacteria, UV treatment or chlorination at the well is the standard approach. For nitrate and TDS, reverse osmosis is effective. Our water filter guide explains options for both scenarios. Pull your detailed report for historical data, and see our Texas page for statewide patterns.