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.
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