Abstract
“Can the wells in my community withdraw water from my aquifer over the next 30 years?” This is the most-asked question to the hydrogeologists at the Illinois State Water Survey (ISWS). One of the greatest strengths of the ISWS is that it houses 150 years of water withdrawal, observed water level, and sampled water quality data. Further, the ISWS has the luxury of decades of development and evolution of a geologic framework, culminating in a regional groundwater flow model developed in MODFLOW.
In this presentation, I will discuss recent work in the southwest suburbs of Chicago using the MODFLOW model developed by the ISWS. Communities in this region must decide whether to stay on their local aquifers or switch to surface water, which brings with it greater water security but also the need for expensive infrastructure. There are two viable aquifers in the region, but each is complicated with its own risks. The shallow aquifer is at-risk of contamination, while the deeper aquifer is at-risk of depletion due to unsustainable withdrawals. Groundwater flow models are a key tool to making decisions, but uncertainty in models creates frustration with stakeholders who “don’t want all of these details, just give us a single number that we can pass to our mayors so they can make a decision.”
I will explore two important aspects that must be considered when using models to explore questions where definitive answers are desired, such as “what is the remaining life of an aquifer?”. First, history matching is a very common approach to evaluating model performance by comparing to observed data. However, great care must be taken to understand data variability/uncertainty and structural error in a model. Second, scenario planning is important to robustly evaluate plausible futures. This is challenging, as communication with stakeholders often reveals potential futures that scientists might not have considered.
Communication is key when presenting uncertainty to sponsors and stakeholders. Presenting uncertainty without proper context may lead to indecisiveness in the planning process, while selecting a single scenario could result in uninformed decisions. In this presentation, I will highlight strategies that the ISWS has used to communicate uncertainty in a clear and understandable manner to stakeholders and decision makers, forcing them to confront the uncertainty facing their water supply.
Bio
Daniel Abrams has a Ph.D. in Environmental Science from Indiana University’s School of Public and Environmental Affairs. He is the lead groundwater flow modeler with the Illinois State Water Survey, specializing in water supply investigations in Illinois. He also is responsible for communicating model results to the public and using feedback to improve models or develop scenarios useful for water supply planning. In the past three years, Daniel has been working closely with the communities and industries in northern Illinois to investigate looming water supply issues.