Temporal Changes In Shallow Groundwater Quality In Northeastern Illinois

Abstract

The rapid increase in population and developed land in the Chicago, Illinois, metropolitan area has placed a heavy demand on water resources. The water sources most likely to be developed in this region over the next few decades are shallow aquifers. These shallow aquifers are vulnerable to surface-derived contaminants, and the increase in developed land may be increasing the rate at which groundwater quality is being degraded. Historical shallow groundwater chloride concentrations from the Chicago metropolitan area have been evaluated for data quality and temporal trends. Chloride concentrations are increasing both regionally and for individual wells in the outermost counties of the Chicago metropolitan area, probably due to road salt runoff. Chloride concentrations have increased by over 2 mg L-1 yr-1 in 20 of 28 municipal wells in DuPage County, and by over 4 mg L-1 yr-1 in 5 wells. On the other hand, chloride concentrations are not increasing significantly in most municipal wells in Cook County.