Water-quality assessment of the Cambrian-Ordovician aquifer system in the northern Midwest, United States

Abstract

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Spatial and temporal variability of radium in the Wisconsin Cambrian–Ordovician aquifer system

“…The temporal variability of combined‐Ra levels in the MCOAS in Wisconsin at the regional and individual water utility scales is examined using the Wisconsin Department of Natural Resources' (DNR) Public Drinking Water System compliance data set. Previous studies examine Ra levels at geographic scales ranging from the entire MCOAS (Siegel, ; Stackelberg et al, ; Szabo et al, ; Wilson, ), to more specific regions within the aquifer system (Grundl & Cape, ; Weaver & Bahr, ), and to the local scale (Mathews et al, ). In contrast, the present study examines trends in maximum combined‐Ra measurements in hydrogeologically defined regions of the MCOAS in Wisconsin, and at the scale of water utility well fields in southeast Wisconsin.…”

Groundwater quality in the Cambrian-Ordovician aquifer system, midwestern United States

“…Combined radium concentrations were moderate or high in about 37 percent of the area not buried by younger rocks, whereas they were moderate or high in about 91 percent of the area that is buried by younger rocks. The difference in combined radium concentrations between these two areas has been previously noted (Wilson, 2012) and is attributed to differences in geochemical conditions within the aquifer system that favor the adsorption of radium on aquifer materials where the aquifer is not buried by younger rocks and the release of radium into solution where the aquifer is buried by younger rocks.…”

“…The LUS networks typically consist of observation wells that are relatively shallow, MAS networks typically consist of domestic-supply wells that are intermediate in depth, and PAS networks typically consist of public-supply wells that are relatively deep. A national synthesis of shallow and intermediate depth groundwater quality was reported by DeSimone and others (2014), and a regional synthesis of shallow and intermediate depth groundwater quality from the C-O aquifer system was reported by Wilson (2012). This fact sheet provides a summary of PAS data for 60 public-supply wells sampled in 2014 in the C-O aquifer system (data available in Arnold and others, 2017b).…”

“…Groundwater in large parts of the buried system was likely recharged during the Pleistocene by glacial meltwater (Siegel and Mandle, 1984). Shallow groundwater flows along short flow paths to local streams, whereas deeper groundwater flows along longer flow paths towards major river valleys, Lake Michigan, or downdip structural basins (Wilson, 2012). Groundwater in large parts of the buried system, in far western Iowa, most of Missouri, south-central Illinois, and Indiana, is too saline for drinking-water use.…”

“…Rocks of the C-O aquifer system are mainly marine sandstones and carbonates that are present at the land surface or beneath glacial deposits in southeastern Minnesota, northeastern Iowa, Wisconsin, northern Illinois, and extreme northwestern Indiana (Young, 1992;Wilson, 2012). The rock layers dip and thicken to the south and east into structural basins in southwestern Iowa, central Illinois, and western Michigan.…”