This data release consists of two different datasets, waterborne resistivity profiling data and water quality data collected during profiling.
In fresh water aquifers, the geoelectric resistivity of earth materials commonly has a positive correlation with hydraulic conductivity. In June 2016, continuous resistivity profiling data were collected, as a proxy for streambed hydraulic conductivity, along selected reaches of three rivers in the Delta region of Mississippi. A total of 180 kilometers (km) of continuous resistivity profiles were collected during a two-week span, with 50 km on the Quiver River, 70 km on the Sunflower River, and 60 km on the Tallahatchie River. These river reaches were selected due to groundwater and surface water continuous monitoring stations located alongside each of the streams which allowed comparison among streams and provided some information of surface water-groundwater interaction. Resistivity profiling was done using a ten-channel, direct-current resistivity meter and a floating, multi-electrode cable with 13 electrodes spaced 5 meters (m) apart.
Resistivity measurements are made by transmitting a known current through two electrodes (transmitter) and measuring the voltage potential across two other electrodes (receiver). The multiple channels on the resistivity meter allows for voltage measurements to be made at 10 receivers simultaneously following a current injection. The configuration of the transmitter relative to the receiver(s) is referred to as an array. For this survey a reciprocal Schlumberger array was used, which positions the transmitting pair of electrodes toward the center of the array and the receiving pairs radiating away from the transmitter. The electrical resistance is calculated by dividing the measured voltage by the applied current. The apparent resistivity is determined by multiplying the electrical resistance by a geometric factor. Apparent resistivity is not the true resistivity because a homogeneous, isotropic subsurface is assumed. To estimate the true resistivity or the resistivity structure where the subsurface is heterogeneous and/or anisotropic, the apparent resistivity data were processed using an inverse modeling software program. Since these data have not been modeled they should only be used qualitatively. The resistivity meter used an external global positioning system (GPS) and echosounder to determine the spatial location of the array and the thickness of the water column. The resistivity of the water in the river was measured at the beginning of each profile and at the end of the last profile each day using a field conductivity meter. Data collected within each river include: Latitudelatitude, Longitudelongitude, injected current, voltage, resistance, apparent resistivity, electrode location (referenced to the position of the GPS), water depth, water temperature, water conductivity, and calculated water resistivity.