Hydrology

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  Coarse-grained Materials Within 50 Feet of the Ground Surface in Illinois
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  Flood Zones for Unincorporated Areas, One-Hundred and Five-Hundred Year
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  Illinois Center Pivot Irrigation
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  Illinois Municipal Water Use, 2012
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  Major Aquifers
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  Major Bedrock Aquifers at Depths Greater Than 500 Feet Below Ground Surface
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  Major Bedrock Aquifers Within 300 Feet of Ground Surface
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  Major Bedrock Aquifers Within 500 Feet of Ground Surface
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  Major Sand and Gravel Aquifers
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  Northeast Illinois Shallow Bedrock Potentiometric Surface
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  Potential of Agricultural Chemical Contamination of Aquifers
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  Reservoir Observation Network
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  Sediment Monitoring Network
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  Shallow Groundwater Wells Network
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  Sinkhole Areas (an indicator of karst terrain)
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  Streams and Shorelines
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  Wetlands, National Wetlands Inventory, 1987