IRRIGATION DEVELOPMENT AND MANAGEMENT ALTERNATIVES OF A DOLOMITE AQUIFER IN NORTHEASTERN ILLINOIS

ABSTRACT: Irrigation development of the dolomite aquifer in eastera Kankakee and northern Iroquois Counties, Illinois, is extensive and increasing. Interruptions of domestic supplies have been reported with increasing frequency during the 1980's. To address this issue, a regional assessment of the ground‐water resources of the region was conducted in 1987 and 1988. Options for managing the dolomite aquifer were also investigated. Hydrogeology of the dolomite aquifer was determined using five aquifer tests. Tranamissivity values of the dolomite aquifer ranged from 14,000 to 50,000 gpd/ft (168 to 600 m³/m/day). Storage coefficients were between 0.0001 and 0.0002, within the range of a confined (artesian) aquifer. Based on flow‐net analyses, recharge of the dolomite aquifer ranged from 85,000 to 285,000 gpd/mi² (124.4 to 417.0 m³/day/km²). Water levels of the dolomite aquifer were mapped during five periods in 1987 and 1988 by measuring up to 226 wells completed in the dolomite aquifer. Maximum regional water‐level declines because of irrigation pumpage were 44 feet (13.4 m) in 1987 and 72 feet (21.9 m) during the drought of 1988. Based on ground‐water use data, precipitation records, and hydrogeologic information, the magnitude of water‐level declines can be attributed more to differing hydrogeologic conditions than to pumpage or climatic changes. Existing ground‐water management methods for resolving conflicts over the ground‐water resources of the study area are reviewed and alternative management options explored.