Hydrogeologic and geochemical characteristics of the Ogallala and White River aquifers, Cheyenne, Wyoming

Water-Resources Investigations Report 2000-4188




The Ogallala aquifer and the underlying White River aquifer are important ground-water resources of public and private drinking water in the Cheyenne, Wyoming area. In 1997, as part of a cooperative project between the Cheyenne Board of Public Utilities and the U.S. Geological Survey, a well was installed to develop information for those two aquifers. Information provided for the Ogallala aquifer included core descriptions, geophysical logs, water levels, aquifer transmissivity, water quality, isotopic analysis, and geochemical modeling. Information for the White River aquifer was limited to core descriptions and geophysical logs.Evaluation of the core obtained from the drill hole showed the sediments to be primarily sands, silts, and clays. The thickness of the Ogallala Formation at the well site was estimated to be 246 feet. Water levels and precipitation from October 1, 1998 to September 30, 1999 indicated that water levels responded to precipitation. During that time, water levels ranged from 6,002.41 feet to 6,004.27 feet above mean sea level. The transmissivity was estimated to be 1.1 feet squared/day. The temperature differences between the municipal water and the Ogallala aquifer water were examined in relation to selected hydraulic conductivities and it was found that the warmer municipal water would slightly increase the hydraulic conductivity if the water were injected into the Ogallala aquifer.The water quality of a sample from the Ogallala 1 well indicated the predominant major ions were calcium, magnesium, and bicarbonate. Isotopic analyses of hydrogen-2, tritium, chlorine-36, carbon-14, and carbon-13 indicated the water was a mixture of pre- and post-1953 recharge. A simple geochemical mixing model indicated there was the potential for dissolution of anhydrite, calcite, gypsum, and dolomite and precipitation of goethite, hematite, pyrolusite, and amorphous ferric hydroxide if municipal and Ogallala aquifer waters were mixed.

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Hydrogeologic and geochemical characteristics of the Ogallala and White River aquifers, Cheyenne, Wyoming
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Water-Resources Investigations Report
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1 over-size sheet.