Shallow Groundwater Sampling in Kane County, 2015

In October 2003, scientists from the Illinois State Water Survey (ISWS) sampled 75 shallow wells for water -quality analysis in Kane County to provide a “snapshot” of groundwater quality in these shallow aquifers, and to compare water quality from different pa rts and aquifers of Kane County. In the fall of 2015, the study was repeated to assess how groundwater quality had changed since 2003. Sixty -eight wells were sampled in 2015, 55 of which had been sampled in 2003. The quality of shallow groundwater in Kane County is generally good, especially in the western and central thirds of the county. However, the total dissolved solids (TDS) values of samples from the eastern third of the county were significantly higher than elsewhere in the county; chloride was the ion of greatest concern. Two- thirds of the samples from the eastern wells sampled had TDS and/or chloride concentrations above their drinking water standards. Road- salt runoff is most likely the major source of elevated TDS and chloride. Of the wells samp led in both 2003 and 2015, about 60 percent had higher TDS values in 2015, with three having increases greater than 100 mg/L. The average increase for the wells with increasing TDS values was 50 mg/L. The increase in TDS is entirely explained by increases in chloride and sodium concentrations, which increased in 78 percent and 59 percent of the wells, respectively. The average increase for wells with increasing values was 25.4 mg/L for chloride and 19.2 mg/L for sodium. The average rate of increase in chlor ide concentrations in the urban eastern third of Kane County was 3.9 mg/L/yr, which is similar to rates found in other studies in northeastern Illinois.published or submitted for publicationis peer reviewedOpe

Groundwater Flow Models of Illinois: Data, Processes, Model Performance, and Key Results

The Illinois State Water Survey (ISWS) has a long history of developing groundwater flow models to simulate water supply and groundwater contamination issues in the state of Illinois. However, past local- and regional-scale models developed by the ISWS have traditionally been project based; thus models are archived when the project is completed and may not be updated for many years. This report presents the first version of the Evolving Network of Illinois Groundwater Monitoring and Modeling Analyses (ENIGMMA), which is the framework of data, procedures, protocols, and scripts that facilitate the development of a single, continuously updated groundwater flow model and other outputs (hydrographs, maps, animations of groundwater potentiometric surfaces). This report focuses on five aspects of ENIGMMA: 1. The archived models and high-resolution datasets that serve as inputs to ENIGMMA 2. The procedures for developing model-ready datasets from these inputs 3. The Illinois Groundwater Flow Model (IGWFM), which serves as the single model that will be continuously updated by ENIGMMA 4. The ISWS Calibration Toolbox, used to facilitate a transient calibration of the IGWFM 5. Animations of groundwater potentiometric surfaces using head-specified models This report is a living document that will be updated periodically. Future updates to this report will focus on additional aspects of ENIGMMA, including the automated development of model-ready inputs and display of model outputs. Updates to this report will also chronicle any additional geologic data added to ENIGMMA, and subsequently, to the Illinois Groundwater Flow Model. Updates will also highlight both local- and regional-scale advancements made with the model, including any key results from these models. The current version of the IGWFM combines and expands on two existing groundwater flow models: 1) the Northeastern Illinois Cambrian-Ordovician Sandstone Aquifer model and 2) the East-Central Illinois Mahomet Aquifer model. In addition, the model incorporates new geologic information developed by the Illinois State Geological Survey in the Middle Illinois Water Supply Planning region. The current model domain covers large portions of Illinois, Wisconsin, Indiana, and Michigan. This large spatial extent is necessary to capture the far-reaching regional head declines in the deep Cambrian-Ordovician sandstone aquifer system, which can extend beyond state boundaries. Depicting some shallow, unconsolidated aquifers also requires a simultaneous simulation of the deep sandstone to account for flow exchange between units. This is because the low-permeable stratigraphic units (aquitards) overlying the sandstone aquifers are absent over large areas of northern Illinois or are locally punctured by wells with long, open intervals. To capture these complex flow pathways, the three-dimensional IGWFM explicitly simulates all geologic materials from the land surface to the impermeable Pre-Cambrian crystalline bedrock. The IGWFM does not currently include a groundwater flow simulation of the southern portion of the state where the deep basin sandstones are highly saline and not used for water supply. Incorporating the shallow aquifers in the southern portion of the state into the IGWFM is a long-term goal. The primary datasets currently incorporated into IGWFM include surface water elevations, annual groundwater withdrawals, well information such as open intervals, geologic 2 surfaces, measured water levels, and aquifer properties inferred from previous modeling studies. These datasets are input at their best available spatial and temporal resolutions, allowing for the development of refined local-scale models. Such local-scale models are essential for simulating groundwater-surface water interactions, well interference, and contaminant transport. Major local-scale models already exist for the Mahomet Aquifer, Kane County, and McHenry County. The IGWFM can address a number of water supply planning questions, particularly the impacts of historic, modern, and future high-capacity groundwater withdrawals on heads and groundwater discharging to surface waters. In addition, where detailed geologic information of the shallow aquifers is available, the IGWFM can also simulate the subsurface migration of point (e.g., volatile organic compounds) and nonpoint (e.g., chloride and nitrate) contaminants.published or submitted for publicationis peer reviewedOpe

Water Supply Planning: Middle Illinois Progress Report

This report presents a summary of 1) the technical information assembled to describe existing water availability and sources of supply within the 7-county (LaSalle, Livingston, Marshall, Peoria, Putnam, Stark, and Woodford Counties) Middle Illinois River Region in central Illinois (Figures 1 and 2) and 2) the development of preliminary computer models that will be used in future studies to estimate impacts to water availability resulting from future water development in the region. Through funding by the Illinois Department of Natural Resources (IDNR), the Illinois State Water Survey (ISWS) and Illinois State Geological Survey (ISGS) prepared this document for the Middle Illinois Regional Water Supply Planning Committee (MIRWSPC) to aid in the development of a plan for meeting the future growth of water supply demands within the basin to the year 2060. It contains background information to provide an overview of management criteria and an understanding of the constraints and policies used in conducting analyses and making decisions concerning water usage. Models will be applied to a broad range of conditions, including a set of selected future water use scenarios to more fully characterize water availability within the Middle Illinois River Region to the year 2060. In addition, as the MIRWSPC deliberates and prepares its water supply planning document, the information presented in this report will be reviewed and, in some cases, additional analysis may be performed and results revised. A more complete reporting of the model development, the results of the scenario simulations, and subsequent work concerning water availability will be published at the end of that forthcoming study. The existing technical information compiled as the first task of this study includes a review of previous analyses and publications dealing with the Middle Illinois River Region’s water resources; collection of hydrogeological and hydrologic data, primarily as needed for modeling; and, in certain cases, additional analyses of that data, such as data mining of well records and yield analyses of surface water supply sources. This compiled information focuses on the three primary sources of water supply within the Middle Illinois River watershed: 1) direct withdrawals from the Illinois River; 2) public supply systems using the Vermilion River and off-channel reservoirs at Pontiac and Streator; and 3) groundwater from within the Middle Illinois River basin. A companion report has been published (Meyer et al., In preparation) evaluating water demand scenarios out to 2060 for the Middle Illinois River, Northwest Illinois, and Kankakee River Regions.published or submitted for publicationis peer reviewedOpe

Changing Groundwater Levels in the Sandstone Aquifers of Northern Illinois and Southern Wisconsin: Impacts on Available Water Supply

In 2014-15, the Illinois State Water Survey conducted their largest synoptic measurement of water levels (i.e., heads) in Cambrian-Ordovician sandstone wells since 1980. The study covered 33 counties in the northern half of Illinois where demands for water are satisfied, in part, by sandstone aquifers. The Wisconsin Geological and Natural History Survey also measured sandstone wells in 10 counties in southern Wisconsin. These observations were used to generate head contours of the sandstone aquifers. These contours provide insight into the direction and magnitude of groundwater flow. They also can be compared with historic measurements, providing insight into the impact of changing groundwater withdrawals through time. In predevelopment conditions, heads in the Cambrian-Ordovician sandstone aquifers were near or above land surface. Due to pumping from the sandstone aquifers, heads have decreased over time; this decrease is referred to as drawdown. In 2014, drawdown in northeastern Illinois was typically over 300 ft and exceeded 800 ft in the Joliet region. Three factors drove this large drawdown. First, demands for water from sandstone aquifers are much greater in northeastern Illinois than in the rest of the study region. Second, the sandstone aquifers are overlain by aquitards, which are low permeable materials that limit vertical infiltration of water. Third, the Sandwich Fault Zone limits water flowing into the sandstone aquifers of northeastern Illinois from the south. Heads near the center of the cone of depression continue to have a decreasing trend. The more severe drawdown in northeastern Illinois has resulted in local areas where heads have fallen below the top of the sandstone, known as desaturation. Desaturation of a sandstone aquifer can create a number of water quality and quantity concerns. The uppermost sandstone, the St. Peter, was observed to be partially desaturated in portions of Will, Kane, and Kendall Counties under non-pumping conditions. Other areas in these counties are at risk of desaturation under pumping conditions or with the installation of additional wells connecting the St. Peter to deeper, more heavily stressed sandstones. Simulations from a groundwater flow model indicate that the risk of desaturation will increase with increased future withdrawals. Despite the relatively small demand for water throughout much of central Illinois, heads have been declining since predevelopment, likely due to the shale overlying the sandstone. This shale serves as an aquitard, minimizing vertical infiltration of groundwater to the sandstone. Sustained drawdown in this region could potentially induce flow from the southern half of the state, where water in the sandstone is highly saline and not suitable as a drinking water supply. Drawdown in northwestern Illinois was also typically small (<100 ft), primarily due to two factors: 1) low demands from the sandstone aquifers and 2) the absence of shale aquitards. The notable exception is in Winnebago County, near Rockford, where demands are historically high and drawdown was on the order of 100-200 ft. While the quantity of water in the aquifer is not a concern in this region, large withdrawals could result in reductions of natural groundwater discharge to surface waters, impacting stream ecosystems under low flow conditions. Drawdown since predevelopment was over 300 ft in southeastern Wisconsin, with the greatest drawdown in Waukesha County of over 400 ft. Recent trends indicate heads in the Waukesha area are recovering, although they are still well below predevelopment levels. [This report is also associated with the fact sheets: Changing Groundwater Levels in the Cambrian-Ordovician Sandstone Aquifers of Northern Illinois, 1980-2014, Groundwater Availability in Northeastern Illinois from Deep Sandstone Aquifers, and Sources of Water for Communities in Northeastern Illinois.published or submitted for publicationis peer reviewedOpe

Groundwater Depletion in Chicago's Southwestern Suburbs

Sandstone aquifers in Illinois have been important sources of water for municipalities and industries since the mid-1800s, and remain important in Will, Kendall, Kane, and McHenry Counties (Figure 1a). Long-term withdrawals have resulted in declining groundwater levels (also known as heads), with the greatest declines of over 900 feet in Will County, locally exceeding 1,100 feet when wells are pumping.published or submitted for publicationis peer reviewedOpe

Changing Groundwater Levels in the Cambrian-Ordovician Sandstone Aquifers of Northern Illinois, 1980-2014

published or submitted for publicationis peer reviewedOpe

Groundwater Availability in Northeastern Illinois from Deep Sandstone Aquifers

published or submitted for publicationis peer reviewedOpe

Water Supply Planning: Middle Illinois Assessment of Water Resources for Water Supply-Final Report

Illinois Department of Natural Resourcespublished or submitted for publicationis peer reviewedOpe

Water supply planning: Kankakee watershed assessment of water resources for water supply

This report examines the impacts of current and future demands on water supplies for the Kankakee Watershed Water Supply Planning Subregion (WSPR) in northeastern Illinois, an area comprising most of Kankakee and Iroquois Counties and portions of Ford, Will, Vermilion, and Grundy Counties that intersects the Kankakee River watershed boundary. Initial water demand scenarios were developed for a three-county region (Ford, Iroquois, and Kankakee) out to 2060 for five major water sectors, including thermoelectric power generation, public supply, self-supplied domestic, self-supplied industrial and commercial (IC), and self-supplied irrigation, livestock, and environmental (ILE), and are described in a companion report (Meyer et al., 2019). Total water usage in 2010 was estimated to be 39 million gallons per day (mgd), with two sectors, public supply and ILE, accounting for more than 80 percent of the demand in the region. Most of the ILE demand was for crop irrigation. Self-supplied IC accounted for 13 percent and the domestic sector 6 percent of the usage. Significant water resources are available to meet demands in the Kankakee WSPR, including both groundwater and surface water. Two major aquifer systems occur in the region: (1) productive sand and gravel aquifers, primarily in the south where the Mahomet Aquifer is encountered; and (2) weathered Silurian-Devonian dolomite, which is the most productive aquifer system in the region. Both the dolomite and Mahomet Aquifers are overlain by clay over most of the watershed, limiting leakage from shallower sources. The deeper Cambrian-Ordovician sandstones are generally too saline in this area to use as a water supply, although they are heavily used just outside of the watershed boundary in Will, Kendall, and Grundy Counties. Although the aquifers are generally thought to be adequate to meet most expected future demands, there are some sensitive areas that should be monitored closely. The most important area appears to be southeastern Kankakee and northeastern Iroquois Counties, where demands for irrigation water are highest on account of sandy soils. These demands are met from the dolomite aquifers and have been shown to result in dewatering of the dolomite during the irrigation season.Water quality in the Silurian-Devonian dolomite aquifer system is generally good. At a few locations, nitrate and chloride concentrations are elevated, but at concentrations below their respective drinking water standards. Water moves relatively rapidly from land surface into the Silurian-Devonian dolomite aquifer where it is near land surface, especially in the northern half of the region; aquifer protection activities should be a priority in these areas. The primary surface water sources in the Kankakee WSPR are the Kankakee and Iroquois Rivers. Currently there are four entities withdrawing water from the Kankakee River in the planning region: Aqua Illinois-Kankakee Division, which supplies the city of Kankakee, the city of Wilmington, Exelon Dresden Station, and Exelon Braidwood Generation Station.Although the Kankakee River has reliable water for meeting current power generation and public water supply needs, the cooling water withdrawals from the river could be limited on account of protected minimum flows and water temperature criteria. Therefore, both Dresden and Braidwood plants have a considerable storage capacity in their cooling ponds to buffer the impact of the minimum flow restriction. With increasing water demand and potential climate change, the frequency and duration of the minimum flow restriction may be increased in the 2 future. Both power plants using the Kankakee River for cooling water may rely on storage water more frequently.Water demand from within the watershed is not expected to increase dramatically in the future. However, large portions of Will County are at risk to dewatering of the Cambrian-Ordovician sandstone aquifers. As a result, communities within these at-risk areas are seeking alternate water supplies in anticipation of these impacts. One possible option is the Kankakee River. As part of the process of exploring alternative supplies, both Joliet and Godley have requested withdrawing a large amount of water from the lower reach of the Kankakee River. The communities served by this water lie primarily outside of the watershed, so both withdrawal and consumptive use of Kankakee River water could increase substantially. Unlike within the watershed, water demand for these communities outside of the watershed is expected to increase. Another unknown is how water demand will be met in the future by industries along the Des Plaines River. Many of these industries also rely on the at-risk sandstone aquifers, so the long-term viability of their sandstone wells is contingent on decisions by communities.The major concern with increasing water demand on the Kankakee River is the minimum flow restriction and how to supplement the river water when it is not available during drought conditions, especially when the water is diverted out of the watershed, as the wastewater may not be returned to the river. Other backup supplies are of limited availability in areas of sandstone risk, as currently the sandstone aquifers are likely to be the only viable backup option; however, there are questions about its viability under increasing demand. Off-channel storages and/or abandoned storage pits could also be explored to provide additional backup supply.As a result, conjunctive water management that accounts for impacts on both river and groundwater supplies will be essential moving forward. Water users within the Kankakee River watershed should be cognizant of this potential future demand on the river. Available flow on the Kankakee River during low-flow periods may be contingent on whether the communities in Will County also tap into it as a water supply, so water planners currently using or anticipating growth in use of the Kankakee River water should stay informed on planning decisions outside of the region. Sandstone users considering using the Kankakee River as a backup supply are also currently working with the ISWS to evaluate the viability of the Kankakee River as a backup supply under low-flow scenarios on the Kankakee River. This is critically important because of the rapid response of the sandstone aquifer when demands change.Illinois Department of Natural Resourcespublished or submitted for publicationis peer reviewedOpe

Upgrade of Illinois State Water Survey Groundwater Quality Database Year 1 Summary

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