Evaluation of potential paleochannels in the Washita Alluvium and Terrace aquifer, Oklahoma

Abstract

Aquifers comprised of alluvium are often an important source of water for industrial, municipal, and environmental purposes. To best manage and protect these complex hydrogeologic systems, a comprehensive evaluation is needed to monitor and predict their response to stress. Electrical Resistivity Imaging (ERI) was used to image the subsurface architecture of the Washita Alluvium and Terrace aquifer in western Oklahoma up to 110 meter deep. This technique was applied to evaluate the geometry and hydraulic properties of the deposits, and integrated these data with limited well data available in the area.

The Washita Alluvium and Terrace aquifer overlies Permian-age bedrock, forming a boundary detectable by ERI. Previous investigations suggest the alluvial deposit was approximately 36 meters deep. The ERI data suggest a previously unknown paleochannel, up to 90 m deep is present in each of four cross section datasets that run perpendicular to the stream with lengths between 0.83 and 1.95 kilometers. The interpretation was supported by some limited deep borings in the area. The discovery of this deeper component of the aquifer demonstrates interpretations of these systems through traditional methods, such as correlating borehole information, can miss important features due to lack of spatially continuous information.