Do you know where your water comes from? Understanding artificial flows in the Cambrian-Ordovician aquifer system of northeast Illinois through participatory modelling

The Cambrian-Ordovician Aquifer System of Northeast Illinois, one of the most heavily stressed aquifers in the United States, presents unique challenges and opportunities for participatory modelling. In the southwest suburbs of Chicago, heads in the aquifer have declined over 300 meters since predevelopment, with the uppermost St. Peter Sandstone being actively desaturated and heads approaching the top of the Ironton-Galesville Sandstone, the deepest fresh groundwater source in much of the region. MODFLOW modellers at the Illinois State Water Survey have worked alongside water users in the southwest suburbs as they actively pursue alternate water infrastructure; elsewhere in the Northwest suburbs a similar risk is projected by the mid- to late-century. One of the largest sources of uncertainty is artificial leakage through multi-aquifer wells; the Ironton-Galesville Sandstone receives no recharge in the region and is almost entirely dependent on anthropogenic flows. This has severe implications on estimates of sustainability. In this presentation we will highlight our insights from discussions with planning groups and water users in the region as we engage in participatory models for future groundwater availability. Topics of discussion include defining risk in a complex network of interconnected aquifers, implications for sustainability, and decision making under uncertainty.