Watertown Water Hardness & Quality Report (2026)

Watertown, South Dakota, in Codington County — the Codington County seat and northeastern South Dakota's regional commercial hub on the Big Sioux River, a prairie city surrounded by the Coteau des Prairies glacial lakes landscape — receives its municipal water from Watertown Utilities, which draws from the James River alluvial aquifer or the Dakota Sandstone aquifer through production wells in the Codington County glacial plain. Northeastern South Dakota's water supply depends primarily on the deep glacial drift and Cretaceous sandstone aquifer systems of the Great Plains.

The moderately hard 163.5 mg/L hardness and TDS of 398.8 mg/L reflect the Codington County glacial aquifer's carbonate character. The glacial drift aquifer beneath the northeastern South Dakota Coteau des Prairies contains reworked Cretaceous Pierre Shale and Niobrara Chalk calcareous material from glacial erosion, along with Silurian and Ordovician carbonate gravels transported by Pleistocene glaciers from the north. The Dakota Sandstone aquifer is a Cretaceous marine sandstone formation with calcareous cement and interbedded calcareous shale layers — both formations contribute moderate dissolved calcium and magnesium bicarbonate to the northeastern South Dakota groundwater supply.

At 163.5 mg/L, Watertown's water is moderately hard — consistent with the northeastern South Dakota glacial aquifer supply. Scale builds in kettles and coffee machines over months, dishwashers benefit from rinse aid, and faucet aerators need periodic cleaning. Quarterly descaling of heating appliances is the standard schedule. The PFAS level of 2.0 ppt is excellent — among the lowest in the Great Plains dataset — reflecting Codington County's rural agricultural character, limited industrial activity, and the relative isolation of the northeastern South Dakota prairie from major military or industrial PFAS sources.