Hydrologic effects of ground- and surface-water withdrawals in the Milford area, Elkhart and Kosciusko counties, Indiana

Water-Resources Investigations Report 85-4166

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Agricultural irrigation in northern Indiana has increased rapidly since 1975 and might double by the year 2000. In 1982, an average of 2 in. of water was used to irrigate 975 acres of sandy soil in north-central Indiana overlying highly transmissive outwash deposits. Irrigational pumpage was 75% of the summer water use but was less than potential irrigational pumpage because: (1) only one-third of the suitable land was irrigated, and (2) precipitation was near normal for the year. A three-dimensional digital flow model, calibrated with data collected in 1982, was used to simulate four hypothetical pumping plans representing various irrigational schemes and possible rainfall conditions: (1) 1982 acreage irrigated and 1982 (above normal) precipitation; (2) 1982 acreage irrigated and below-normal precipitation; (3) maximum acreage irrigated and normal precipitation; and (4) maximum acreage irrigated and below-normal precipitation. A fifth pumping plan was used to simulate maximum year-round water use. Of the four pumping plans that simulated irrigational pumpage, plan 4 had the greatest effect on ground- and surface-water supply. The model predicted a potentiometric decline of as much as 20.7 ft over an 8-acre area of the aquifer. Streamflow in Turkey Creek would be reduced 39% by simulated groundwater and surface water pumpage but remaining flow would still be twice the 7-day, 10-yr low flow. The rate of pumping used in plan 5 was nearly 4 times the pumping rate in 1982. Potentiometric decline for plan 5 was as much as 40% of available drawdown, and predicted streamflow reduction would cause flow in Turkey Creek to decrease below the 7-day, 10-yr low flow. Results of plans 1, 2, 3, and 4 indicate that the outwash system provides adequate water for current (1982) needs and substantial growth for irrigation. Plan 5 indicates that water use could increase substantially before effects of pumping would prevail year-round. (Lantz-PTT)

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USGS Numbered Series
Hydrologic effects of ground- and surface-water withdrawals in the Milford area, Elkhart and Kosciusko counties, Indiana
Series title:
Water-Resources Investigations Report
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U.S. Geological Survey,
vi, 75 p. :ill., maps ;28 cm.