Water quality of a stream-aquifer system, southern Franklin County, Ohio

The chemical quality of the water resources in the Scioto River valley south of Columbus, Ohio, was evaluated on the basis of data collected from 74 wells and 4 surface-water sites. A very hard calcium bicarbonate water that is high in dissolved solids is characteristic of the aquifer. Mean pH of the ground water is 7.3, and bicaerbonate concentrations range from 238 to 530 milligrams per liter. Concentrations of dissolved iron in water samples (0.01 to 3.9 milligrams per liter) frequently exceed the drinking water standard of 0.3 milligrams per liter established by the Ohio Environmental Protection Agency. The chemical quality of local streams closely resembles the ground-water quality, except for higher concentrations of sodium, chloride, and sulfate in the surface water. Microbiological testing of ground water for fecal bacteria indicated concentrations ranging from 1 to 2,400 colonies per 100 milliliters. The higher concentrations were observed in one well on the Scioto River flood plain after a flood event. Mass-balance calculations of the chemical data indicate that pH is buffered primarily by the carbonate system. Data for pH, calculated Eh, and concentrations of ferrous iron and reduced sulfur show that areas of different chemical environments exist within the aquifer. A reaction model of an induced-infiltration radial collector system indicates the amount of mass transfer (chemical reactions that occur as ground water and surface water mix) is small, and that the mixing ratio between ground and surface waters is four to one.