| | | | Title: | | | | | Volume/Number: | 1965 | | | | Issuing Agency: | | | | | Description: | Recharge conditions in several areas of northeastern Illinois are described, and recharge rates for several aquifers in central and southern Illinois are given. Recharge rates to deeply buried bedrock and sand-and-gravel aquifers vary from 1300 to 500,000 gallons per day per square mile (gpd/sq mi). The lowest rate is for an area where the Cambrian-Ordovician Aquifer is overlain by the Maquoketa Formation consisting mostly of shale; the highest rate is for an area where a sand-and-gravel aquifer is overlain by permeable coarse-grained deposits. Groundwater recharge generally is at a maximum during wet spring months; in many years there is little recharge during the five-month period July through November. The theoretical aspects of recharge from precipitation are discussed; recharge rates vary with the coefficient of vertical permeability, the vertical head loss associated with recharge, and the saturated thickness of deposits through which vertical leakage of water occurs. Recharge rates are not constant but vary in space and time. A summary of coefficients of vertical permeability and leakage of deposits overlying aquifers within the state is presented. Coefficients of vertical permeability of glacial deposits range from 1.60 to 0.01 gallons per day per square foot (gpd/sq ft). The average coefficient of vertical permeability of the Maquoketa Formation is 0.00005 gpd/sq ft. Coefficients of leakage of glacial deposits and bedrock confining beds range from 2.3 x 10-1 to 2.5 x 10-7. Annual ground-water runoff from 109 drainage basins scattered throughout Illinois is estimated with streamflow hydrograph separation methods and flow-duration curves. The relations between groundwater runoffs during years of near, below, and above normal precipitation and basin characteristics such as geologic environment, topography, and land use were determined by statistical analysis. Groundwater runoff is greatest from glaciated and unglaciated basins having considerable surface sand and gravel and underlain by permeable bedrock. Groundwater runoff is least from glaciated basins with surface lakebed sediments and underlain by impermeable bedrock. Groundwater runoff during a year of near normal precipitation ranges from 0.06 to 0.43 cubic feet per second per square mile (cfs/sq mi). Groundwater runoff is at a maximum during spring and early summer months, and is least in late summer and fall months. Annual groundwater runoff depends upon antecedent moisture conditions as well as the amount and distribution of annual precipitation. Because many aquifers in Illinois are deeply buried, not all groundwater runoff can be diverted into cones of depression because there is some lateral as well as vertical movement of water in surface deposits. Data on groundwater runoff can be useful in estimating recharge to aquifers and in evaluating the potential yield of groundwater reservoirs. However, studies indicate that no simple relation exists between groundwater runoff and the potential or practical sustained yields of aquifers. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | RI-48 | | | | ISL ID: | 000000000930 Original UID: 999999993912 FIRST WORD: Ground | |
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