Clarksville Water Hardness & Quality Report (2026)

Clarksville, Indiana, in Clark County — a southern Indiana town directly across the Ohio River from Louisville, Kentucky, the oldest American town north of the Ohio River (platted 1783 as the first US land grant after the Revolutionary War), and home to the Falls of the Ohio State Park — receives its municipal water from the Clark County Water Works or Town of Clarksville Utilities, which draws from the Ohio River at the Louisville Falls reach. Clarksville and the greater Louisville metropolitan area depend on the Ohio River for municipal water supply.

The hard 215.5 mg/L hardness and elevated TDS of 477.7 mg/L reflect the Ohio River's substantial Mississippian carbonate mineral loading at the Falls of the Ohio reach. The Ohio River at Louisville drains an enormous watershed including the Mississippian limestone plateau of Kentucky and Indiana — the St. Louis Limestone, Salem Limestone, and Ste. Genevieve Limestone of the classic Mid-continent Mississippian carbonate sequence. The Falls of the Ohio is itself a famous exposure of Devonian coral reef limestone — the Jeffersonville Limestone (Devonian) — testifying to the prolific carbonate terrain the Ohio traverses above Clarksville. Mississippian and Devonian carbonate plain drainage consistently loads the Ohio River with dissolved calcium, magnesium, and bicarbonate, producing hard, moderately elevated-TDS finished water after treatment.

At 215.5 mg/L, Clarksville's water is hard — scale builds in kettles and appliances within weeks, dishwashers require rinse aid or water softener salt, and bathroom fixtures develop calcium encrustation. Monthly descaling of frequently used heating appliances is practical. A water softener or descaling filter is recommended for Clark County homes with high water use. The PFAS level of 6.8 ppt warrants a certified drinking water filter — the Louisville-southern Indiana metro's industrial corridor, the Indiana Army Ammunition Plant in Charlestown (Clark County), and the Ohio River upstream PFAS industrial discharge sources contribute to the Clark County Ohio River supply's PFAS background.