Clarksville Water Hardness & Quality Report (2026)

Clarksville, Tennessee draws its municipal water supply from the Clarksville Gas and Water Division, sourcing raw water from the Cumberland River at an intake connected to Lake Barkley — a large TVA impoundment created by Barkley Dam on the Cumberland River in Stewart and Trigg Counties. The Cumberland at this point drains a large watershed encompassing much of middle Tennessee and southern Kentucky, collecting flows from the Plateau, Highland Rim, and Nashville Basin physiographic regions. Raw water is treated at Clarksville's Water Treatment Plant in Montgomery County before distribution. Water hardness measures 139.5 mg/L — classified as moderately hard.

Clarksville's moderate hardness reflects the geology of the lower Cumberland watershed where the river crosses the Western Highland Rim physiographic province in northwest Tennessee. The Highland Rim is underlain by Mississippian-age St. Louis Limestone, Warsaw Formation limestone and dolostone, and older Devonian limestone formations — a gently rolling carbonate plateau that forms the rim surrounding the Nashville Basin. As the Cumberland River drains these extensive limestone formations and the numerous karst springs that emerge throughout the Highland Rim, it consistently accumulates moderate calcium and bicarbonate loads before reaching Lake Barkley.

With hardness at 139.5 mg/L, Clarksville residents encounter moderate scale build-up on bathroom fixtures, in kettles, and inside dishwashers over time. Monthly descaling of faucet aerators and showerheads keeps them in good working condition. Kettles benefit from periodic citric acid treatment to remove mineral build-up, and dishwashers produce consistently cleaner results with rinse-aid. Water heaters benefit from an annual inspection for element scale accumulation. Clarksville Gas and Water consistently delivers water meeting all Tennessee TDEC and EPA Safe Drinking Water Act requirements.