INVESTIGATION OF SHALLOW GROUNDWATER QUALITY IN ILLINOIS’ DRIFTLESS AREA: PRELIMINARY RESULTS

Shallow karst groundwater quality in Jo Daviess County, located in the Driftless Area of Illinois, has never been studied systematically. We recently sampled 10 shallow wells (100 – 160 ft) and 10 karst springs across the county to determine chemical and bacterial quality. The well water generally was of good quality, even though the presence of tritium in most of the samples indicated fairly young waters. Only 3 of the wells tested positive for total coliform and none for fecal coliform. Chloride and nitrate levels were also low, suggesting minimal surface-borne contaminants. Spring water quality was generally much worse, as is common in karst systems. Total coliform numbers were often very high, and all but two springs had fecal coliform contamination. Nitrate-N concentrations were generally above background (ca. 2.5 mg/L) and in some cases as high as 12 mg/L. These results are being used to help design a larger study to systematically evaluate the water quality of the shallow karst aquifer in Jo Daviess County.