Round Rock Water Hardness & Quality Report (2026)

Round Rock, Texas, one of the fastest-growing cities in the United States and a major Austin suburb in Williamson County, draws its municipal water supply through the City of Round Rock Utilities and the Brushy Creek Regional Utility Authority (BCRUA), sourcing primarily from Lake Georgetown on the North Fork San Gabriel River in Williamson County, and contracted treated water from the City of Georgetown and other Williamson County sources. The North Fork San Gabriel River and Brushy Creek drain the Williamson County terrain between the Edwards Plateau and the Blackland Prairie transition zone. Water hardness measures 101 mg/L — classified as moderately hard.

Round Rock's moderate hardness reflects the geology of the San Gabriel River watershed in the Williamson County–Edwards Plateau transition zone. Lake Georgetown and Brushy Creek watersheds drain terrain underlain by the Cretaceous Glen Rose Formation (lime mudstone, marl, and reef limestone — the primary Edwards Plateau formation), the Cretaceous Edwards Group (porous dolomite and limestone), and the Comanche Peak Limestone. While this is clearly carbonate terrain, the San Gabriel watershed in this transitional zone shows lower hardness than the full Blackland Prairie–Austin Chalk system further east, reflecting the Glen Rose Formation's somewhat less soluble character compared to the Austin Chalk, and the high-quality spring-fed recharge from the Edwards Plateau.

At 101 mg/L, Round Rock residents encounter moderate scale accumulation. Faucet aerators and showerheads develop deposits after several months — monthly cleaning with citric acid solution is practical maintenance. Dishwashers produce cleaner glassware with rinse-aid, and water heaters benefit from periodic inspection for scale. City of Round Rock Utilities and BCRUA consistently deliver water meeting all Texas TCEQ and EPA Safe Drinking Water Act requirements.