Quality of ground water for selected municipal water supplies in Iowa, 1997–2002 water years

The Iowa ground-water-quality monitoring program has been conducted cooperatively since 1982 by the Iowa Department of Natural Resources, Iowa Geological Survey; the University of Iowa Hygienic Laboratory; and the U.S. Geological Survey. The original objectives of the program were to provide baseline ground-water-quality data throughout the State for the major aquifers and to address any new areas of water-quality concern. Since the program began, the emphasis and objectives of the program have changed several times. As of 1992, greater emphasis has been placed on determining trends in ground-water quality and correlating water quality with possible contributing factors such as location, land use, aquifer, aquifer depth, and precipitation.

From 1997 through 2002, a total of 471 samples of untreated water have been collected from 154 municipal wells throughout Iowa. The samples, collected from six different aquifers, consisted of 192 alluvial aquifer samples (36 wells), 79 Pleistocene aquifer samples (16 wells), 52 Cretaceous aquifer samples (35 wells), 48 Carboniferous aquifer samples (30 wells), 54 Silurian-Devonian aquifer samples (19 wells), and 46 Cambrian-Ordovician aquifer samples (18 wells).

Some samples had concentrations greater than or equal to the respective Maximum Contaminant Levels for drinking water established by the U.S. Environmental Protection Agency. Of 471 samples analyzed, 19 samples had concentrations greater than or equal to the Maximum Contaminant Level for sulfate; 31 samples had concentrations greater than or equal to the Maximum Contaminant Level for nitrite plus nitrate; 257 samples had concentrations greater than or equal to the Secondary Maximum Contaminant Level for iron; and 249 samples had concentrations greater than or equal to the Secondary Maximum Contaminant Level for manganese. Of the 443 samples analyzed for pesticides, 87 samples had concentrations greater than or equal to the respective minimum reporting levels for the parent compounds, 30 samples had concentrations greater than or equal to the respective minimum reporting levels for pesticide metabolites, and 26 samples had detectable concentrations (censored values) less than the minimum reporting levels. Concentrations of alachlor, atrazine, cyanazine, and metolachlor accounted for about 90 percent of the samples equal to or exceeding the respective minimum reporting levels for pesticides. No samples had pesticide concentrations greater than the respective Maximum Contaminant or Health Advisory Levels.

The compact disc included with this report has information about water-quality properties and concentrations of dissolved solids, major ions, nutrients, trace elements, radionuclides, total organic carbon, pesticides, and synthetic organic compounds for water years 1997 through 2002.