Koster, John W., authorHarry, Dennis L., authorColorado State University, publisher2020-01-302020-01-302005https://hdl.handle.net/10217/200601http://dx.doi.org/10.25675/10217/2006012005 annual AGU hydrology days was held at Colorado State University on March 7 - March 9, 2005.Includes bibliographical references.Electrical resistivity surveys were conducted of an unconfined fluvial aquifer in Columbus, MS. The aquifer consists of an upper 3 m thick clayey-silt flood plain facies containing clay and silty-clay filled channels and a lower 5 m thick braided stream facies consisting of sand and gravelly-sand. A survey conducted in 2002 imaged the aquifer in a drained state. It was re-surveyed in 2004 when saturated. The geometry and positions of the two surveys are identical, so changes in resistivity are a direct result of aquifer saturation. The data was inverted to produce cross sections of resistivity in the saturated and drained aquifer. The difference in resistivity shows that water saturation decreases resistivity in the upper flood plain facies by 0 to 600 ohm-m, with the creates change outside the channels in the clayey-silt flood plain deposits. In the channels, the resistivity remains approximately unchanged. This is attributed to the low permeability of the clay, which does not allow water to enter the channel fill. In the braided stream facies, resistivity increases with saturation by 0 to 1100 ohm-m. The largest increases are in the poorly sorted gravel-bearing deposits. Channels and major lithologic boundaries are well constrained in both the saturated and unsaturated state, indicating that resistivity images of drained outcrops provide a reliable analog that can be used for interpretation of data from buried, saturated aquifers.born digitalproceedings (reports)engCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.Text