Modeling the Sediment Fill of the Upper Troy Pre-Glacial Bedrock Valley, McHenry County, Illinois, USA

The Troy Bedrock Valley (TBV) and its tributary valleys are the principal pre-glacial drainage in southern Wisconsin and northern Illinois, USA. This study focused on the headwaters of a tributary that occurs in McHenry County, IL. Drilling, geophysical surveys, and the analysis of existing geologic and water well data were used to determine the lithologic and geometric characteristics of the sediments that fill the paleovalley. A 3D geologic model of these sediments was then developed in Petrel. More than 65 m of Quaternary sediments filled the paleovalley. The model domain covers approximately 30 km2. The valley drains to the west and meanders, which is distinct from the straight course of the overlying modern Kishwaukee River. The sediments that filled the valley were subdivided into five units. These units include Illinois-age Glasford Formation coarsegrained proglacial outwash and alluvial deposits (GS2, GS1) and fine-grained lacustrine and diamicton deposits (G2 and G1). The Wisconsin-age Henry Formation sand and gravel cap the valley fill, and Cahokia alluvium buries everything

Stratigraphy and Extent of the Pearl-Ashmore Aquifer, Mchenry County, IL, USA

Quaternary glacial till, outwash, lake sediments, and loess compose the surficial deposits of McHenry County, Illinois. Much of the landscape of McHenry County were formed by at least three separate advances of the Harvard Sublobe of the Wisconsin Episode Lake Michigan Lobe, which was part of the Laurentide Ice Sheet. This project focuses on the delineation of the stratigraphy and extent of the Pearl-Ashmore Aquifer. The Pearl-Ashmore Aquifer is the combination of the proglacial outwash of the Wisconsin Episode Ashmore Tongue of the Henry Formation and the youngest outwash associated with the Illinois Episode, which is the Pearl Formation. A 3-D geologic model was generated from a number of different subsurface geologic data sets, including geologic borings, and municipal and private water well records. These data were initially visualized and interpreted in the 3-D environment using ESRI’s ArcScene. More than 700 wells were used to construct the model. The stratigraphic picks were imported into Petrel, and horizons were created from the surface data to complete the 3-D geologic model. Isopach maps of each unit were then created. The Pearl-Ashmore Aquifer extends through the eastern two-thirds of McHenry County. The 3-D geologic model predicts that the aquifer has an average thickness ranging from 5 to 15 m and is thickest in the north-central portion of McHenry County where it can reach thicknesses of up to 40 m

Role of Multiple High-Capacity Irrigation Wells on a Surficial Sand and Gravel Aquifer

Within McHenry County, IL, the fastest growing county in Illinois, groundwater is used for 100% of the water needs. Concerns over water resources have prompted the investigation of the surficial sand and gravel aquifers of the county. While the eastern portion of the county is urbanizing, the western portion remains devoted to agriculture. High-capacity irrigation wells screened within the surficial sand and gravel aquifer are used for crop production. To assess the impacts of the irrigation wells on the aquifer, a groundwater flow model was developed to examine five different scenarios reflecting drought conditions and increased pumping. Results show that the surficial sand and gravel aquifer is capable of meeting current water demands even if recharge is decreased 20% and pumping is increased 20%. The additional loss of discharge and increases in pumping result in head differences throughout the aquifer

The future of science of the Mahomet aquifer

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Northeastern Illinois Water Supply Planning Investigations: Opportunities and Challenges of Meeting Water Demand in Northeastern Illinois

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