IPS Model

Prioritizing High-Impact Restoration Projects

Restoring the health of rivers and streams in northeastern Illinois will take time. With so much to do, how can we prioritize projects that will have the greatest impact? The DuPage River Salt Creek Workgroup (DRSCW), in collaboration with Midwest Biodiversity Institute, first developed the Integrated Prioritization System (IPS) Model in 2011 to answer that question for their watershed area.  

The model has been updated in 2020, in partnership with the Lower DuPage River Watershed Coalition, the Des Plaines River Watershed Workgroup and the North Branch Chicago River Watershed Workgroup. The model was expanded to utilize data from wadeable streams from across northeastern Illinois provided by the Illinois Environmental Protection Agency, Illinois Department of Natural Resources and the project partners. This expanded data set helped to fill in the gradient from poor quality to high quality aquatic communities. 

How the Model Works

Rivers and streams that flow through an urbanizing landscape are impacted by a myriad of pollutants, structural impediments and problems associated with the quantity and quality of stormwater and wastewater that is directed into them. We consider all of these things to be “stressors” to aquatic life. The fish and macroinvertebrate (aquatic bugs) data that we collect tells us the health of the aquatic community, which reflects the compilation of all of these stressors. Fewer stressors allow greater biological diversity and signals better stream health. In contrast, more stressors limit biological diversity and indicate poorer health. 

The IPS Model takes all of the bioassessment data we collect (biological, chemical, and physical) and other information like land use, canopy cover, and road density and analyzes it at the reach and watershed scale. The output is the relative impact of each stressor or groups of stressors and allows us to rank them in order of importance – which stressors have the greatest impact to aquatic life. The model also provides a threshold for many stressors identifying the point at which a stressor causes fish or bug scores to decline.   

Based on the fish and bug scores, the ranking of stressors and how stream segments compare to the thresholds for various stressors, the IPS Model provides a restorability measure that indicates the relative difficulty or ease of restoring part of a stream. The measure allows our watershed groups to prioritize projects that will make the most progress to restore stream segments. Ultimately, we get an updated list of priority projects from the IPS Model.  

Stressors to aquatic life
IPS monitoring sites - click to expand