ISWS researchers use advanced, long-term monitoring techniques, comprehensive databases, and modeling tools to evaluate and improve water quality across Illinois. These insights inform resource managers, policymakers, and communities in urban and rural areas, helping protect public health and sustain vital surface and groundwater resources.
Runoff
Nitrogen and Phosphorus
Illinois’ watersheds are particularly vulnerable to nutrient runoff due to intensive agriculture. Excess nitrogen and phosphorus from farms, city streets, and wastewater treatment plants contribute to harmful algal blooms, reducing oxygen levels essential for aquatic life, including downstream in the Gulf of Mexico.
ISWS scientists monitor nutrient levels in key Illinois watersheds, such as the Sangamon, Kaskaskia, and Fox rivers, to assess the effectiveness of the Conservation Reserve Enhancement Program (CREP). In this project, ISWS researchers evaluate the success of conservation practices and land management in reducing runoff. A watershed simulation model, combined with multi-objective evolutionary algorithms (MOEAs), optimizes these practices and guides data-driven watershed management plans. Learn more about our watershed monitoring to support the CREP program.
In other projects, scientists simulate the transport of nitrate from the surface to aquifers below by building and refining groundwater flow models. Also, ISWS samples nitrates in groundwater studies and collects the contaminants at certain ISWS streamgages. Examining the sources and pathways of nitrates is vital in developing strategies to protect water resources.
Chloride
Road salt from winter deicing has been a significant concern for groundwater quality, especially in urbanized regions of Illinois, since the 1950s. Chloride from road salt infiltrates shallow groundwater reserves, leading to contamination in lakes, rivers, and wells. While chloride is not a public health concern, it is an indicator of impaired groundwater quality and leads to corrosion of water infrastructure. ISWS researchers analyzed over 4,600 public and private well samples between 1906 and 2005, identifying rising chloride levels in Cook, DuPage, and surrounding counties. Their findings help inform better salting practices, contributing to efforts to reduce groundwater contamination and maintain water quality.
In 2023, ISWS researchers received the Salt Symposium’s Chloride Reduction Leadership Award, which recognizes individuals and groups that have made a significant contribution to chloride reduction. ISWS researchers are actively modeling chloride movement in aquifers throughout northeastern Illinois using groundwater flow models.
Contaminants of Concern
PFAS, PPCPS, and Microplastics
Emerging contaminants such as PFAS (per- and polyfluoroalkyl substances), pharmaceuticals and personal care products (PPCPs), and microplastics are increasingly recognized for their potential to contaminate water resources. ISWS researchers are investigating the fate and behavior of these and other contaminants. These studies enhance our understanding of how these contaminants move through both groundwater and surface water systems, guiding efforts to manage and mitigate their impacts.
Heavy Metals and Minerals
Lead from pipes is a heavy metal of concern because of its potential health risks. In 2019, ISWS researchers conducted studies in Jackson, Peoria, and Kane counties to determine lead levels in private homes. Elevated lead levels were found in 48% of well water samples, particularly in samples from older homes or areas with corrosive groundwater. These findings aim to assist well owners in reducing exposure and improving water quality.
Arsenic and radium are naturally occurring contaminants derived from minerals. Previous studies indicate that these contaminants vary across the state, depending on local aquifer conditions.
A team from the University of Illinois Urbana-Champaign, which includes ISWS scientists, and Washington University is developing a drinking water quality system that evaluates the ability of commercially available water filters to monitor lead, copper, arsenic, PFAS, and other chemicals linked to adverse health outcomes. The research aims to support residents who use private wells and public water systems in disadvantaged communities.
Legionella Bacteria
Legionella is a growing concern in both public water supplies and private wells. Legionella occurrence in home plumbing systems is not well understood, but ISWS researchers are currently examining possible mechanisms of Legionella occurrence in homes that use private wells as their water source. The Private Well Class leads a water testing effort for homes using private well water as their drinking water source in Illinois. The results so far are mixed and have led to numerous additional questions about Legionella, biofilms, and bacterial growth in hot water lines in residential settings.
Suspended Sediments
Sediment transport can significantly degrade water quality and harm aquatic ecosystems. The Benchmark Sediment Monitoring Program, launched by ISWS in 1981, provides critical insights into ongoing sediment dynamics across Illinois rivers and streams. Trained local citizen scientists and ISWS staff collect water samples on the same exact date, time, and stream stage. These long-term data trends can be used to evaluate watershed management efforts by identifying high-erosion areas and assessing the impact of conservation practices aimed at reducing soil loss and sediment delivery. The Sediment Materials Lab measures suspended sediment concentrations and particle sizes and provides water analysis services to University of Illinois staff, external researchers, and the public.
Regional Water Quality Assessments & Water Quality Databases
ISWS has a long history of conducting regional and countywide water quality studies in surface water and groundwater systems, providing data to help identify long-term trends in contaminants such as lead, arsenic, chloride from salt deicers, and emerging contaminants like PFAS. For example, the Illinois Coastal Zone Water Quality Database (ICoastalDB), funded by the Illinois Department of Natural Resources, compiles data from multiple agencies and can assess 200 water quality parameters in Illinois’ coastal regions. ISWS researchers recently completed a 20-year groundwater quality study at private wells in Kane County, showing how land use impacts aquifers. Finally, the ISWS developed the Illinois Shallow Groundwater Vulnerability Map with the Illinois Department of Natural Resources. The map depicts subsurface zones comprising sand and gravel aquifers and the upper 100 feet of bedrock, with heightened potential for contaminant migration into and within groundwater.
ISWS maintains groundwater quality databases that serve as crucial resources for understanding water quality conditions in Illinois over time. Using data compiled from various sources, the Groundwater Quality Database offers detailed information on a location or facility’s specific well, well depth, aquifer tapped, sample date, sample number, and water quality parameter(s). It contains over 60,000 samples collected since 1890, covering historical and ongoing groundwater quality data. These databases and resources support research efforts, inform policy decisions and Illinois residents, and guide conservation and management practices to protect water resources across the state over time.