Bedrock geologic map showing thickness of overlying Quaternary deposits, Fremont Quadrangle and part of Omaha Quadrangle, Nebraska

Burchett, Raymond R.; Reed, E. C.; Dreeszen, Vincent H.; Prichard, G.E.

doi:10.3133/i905

Cited by 4 publications

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Conjunctive Use of Geophysical and Geological Data in the Study of an Alluvial Aquifer

Ayers

1989

Groundwater

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A geoelectric survey, composed of vertical electrical soundings, was conducted over part of the lower Platte Valley alluvial aquifer of east‐central Nebraska. Survey results, in conjunction with seismic‐survey data and test‐ hole‐log information, provided the basis to map the areal extent and thickness of a near‐surface, low‐permeability clay unit. Because of the low hydraulic conductivity of the clay, the unit forms a confining layer over a significant part of the aquifer. Generally, the approach to evaluating the lower Platte Valley alluvial aquifer for sustained yield has been to assume that the entire flow system is under water‐table conditions. However, numerical‐model simulations with and without the clay unit indicate that this confining layer has a significant effect on the hydraulic behavior of the groundwater flow system under pumping stresses. An estimate of the bulk porosity of the aquifer was made by using geoelectric data and applying the Archie equation. Values of porosity ranged from 0·27 to 0·43; although reasonable for fluvial sand and gravel, the range is higher than previous estimates.

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