The electrical conductivity of the earth is used to help infer lithological and pore fluid properties. Various geophysical methods can provide estimates of the distribution of below ground electrical conductivity, with each method having certain limitations. This data release presents raw and processed results from land-based and water-based frequency domain electromagnetic induction (EMI) data collected from August 23, 2017 to August 28, 2017. The raw data consist of .csv files from the Geophex GEM-2 unit. Data were primarily collected by walking with the instrument at approximately 1 m off the ground in horizontal coplanar (ski flat) mode. A survey along a section of the Little Wind River in a kayak (with about 0.3 m of elevation above the water surface) was also collected.

The electrical conductivity of the earth is used to help infer lithological and pore fluid properties. Various geophysical methods can provide estimates of the distribution of below ground electrical conductivity, with each method having certain limitations. This data release presents raw and processed results from 9 electrical resistivity tomography (ERT) transects collected from August 24, 2017 to August 28, 2017. The raw data include instrument files from the AGI SuperSting R8 unit (.stg and .crs fils) as well as some electrode positions from those lines recorded with a handheld GPS to help georeferenced the lines. Processed data include data that has been combined (where appropriate), filtered, and converted to a format suitable for inversion with the included R2 v. 3.1 program (Andrew Binley, Lancaster University). Visualization toolkit (.vtk) files of the inverted electrical conductivity are included that have been georeferenced to UTM zone 12T coordinates with elevations in reference to mean sea level. These files are suitable for viewing with Paraview software.

The electrical conductivity of the earth is used to help infer lithological and pore fluid properties. Various geophysical methods can provide estimates of the distribution of below ground electrical conductivity, with each method having certain limitations. This data release presents raw and processed results from hand-caried frequency domain electromagnetic induction imaging (EMI) data collected from June 27-28 along Blacktail Creek near Williston, North Dakota. Data were primarily collected by walking in the creek or along the riparian zones with the GEM-2 instrument (Geophex, Ltd.) at approximately 0.5 m off the ground in horizontal coplanar (ski flat) mode.

This data release contains geophysical data collected at the Little Wind River site near Riverton, Wyoming in 2015 and 2017. The dataset contains:[1] Fiber Optic Distributed Temperature Sensing data (FO-DTS, August-September 2015) collected in the water along the river bank, [2] Electrical Resistivity Tomography data (ERT, August 2017) collected on land near the river bank, and [3] Frequency domain Electromagnetic Induction (EMI, August 2017) data collected along the river and more extensively throughout the study region. Data for each of these methods can be found in the child items linked below.

This data release contains geophysical data collected at the Little Wind River site near Riverton, Wyoming in 2015 and 2017. The dataset contains:[1] Fiber Optic Distributed Temperature Sensing data (FO-DTS, August-September 2015) collected in the water along the river bank, [2] Electrical Resistivity Tomography data (ERT, August 2017) collected on land near the river bank, and [3] Frequency domain Electromagnetic Induction (EMI, August 2017) data collected along the river and more extensively throughout the study region. Data for each of these methods can be found in the child items linked below.

The electrical conductivity of the earth is used to help infer lithological and pore fluid properties. Various geophysical methods can provide estimates of the distribution of below ground electrical conductivity, with each method having certain limitations. This data release presents raw and processed results from land-based and water-based frequency domain electromagnetic induction imaging (EMI) data collected from March 31 to April 2, 2015. Data were primarily collected by walking throughout the wetland and riparian zones with the GEM-2 instrument (Geophex, Ltd.) at approximately 1 m off the ground in horizontal coplanar (ski flat) mode. A survey along a section of the Colorado River in a kayak was also collected (with approximate 0.3 m of elevation above the water surface).

The electrical conductivity of the earth is used to help infer lithological and pore fluid properties. Various geophysical methods can provide estimates of the distribution of below ground electrical conductivity, with each method having certain limitations. This data release presents raw and processed results from land-based and water-based frequency domain electromagnetic induction imaging (EMI) data collected from March 31 to April 2, 2015. Data were primarily collected by walking throughout the wetland and riparian zones with the GEM-2 instrument (Geophex, Ltd.) at approximately 1 m off the ground in horizontal coplanar (ski flat) mode. A survey along a section of the Colorado River in a kayak was also collected (with approximate 0.3 m of elevation above the water surface).

Electromagnetic (EM) geophysical methods provide information about the bulk electrical conductivity of the subsurface. EM data has been widely used to investigate aquifers and geologic structures. In the following study, the United States Geological Survey conducted a boat-towed, waterborne transient electromagnetic (FloaTEM) survey to examine conductivity within the subsurface of the Delaware River channel. These conductive zones determine the location of the groundwater freshwater/saltwater interface within the Delaware River, downstream from Wilmington, DE. The FloaTEM system transmits a primary electrical current through a transmitter loop (Tx) wire. This creates a static primary magnetic field. Then, the current in the TX loop is subsequently turned off, resulting in secondary electrical currents being induced in the earth. These induced electrical currents decay with time, and this rate of decay in the secondary electrical field is a function of the bulk conductivity of the subsurface material. As the secondary electrical field decays, a secondary magnetic field is induced and measured at a receiver (Rx) loop towed behind the Tx loop. The Rx loop measures the decay of the secondary magnetic field as a function of time (dB/dt). Measured dB/dt decay curves can be inverted to recover the depth-dependent resistivity structure of the earth. FloaTEM surveys were conducted downstream from Wilmington, DE on 8/26/2020 and 8/27/2020. Data on 2/26/2020 were collected around the Augustine Wildlife Area boat ramp, and data on 8/27/2020 were collected near the Collins Landing boat ramp.

Electromagnetic (EM) geophysical methods provide information about the bulk electrical conductivity of the subsurface. EM data has been widely used to investigate aquifers and geologic structures. In the following study, the United States Geological Survey conducted a boat-towed, waterborne transient electromagnetic (FloaTEM) survey to examine conductivity within the subsurface of the Delaware River channel. These conductive zones determine the location of the groundwater freshwater/saltwater interface within the Delaware River, downstream from Wilmington, DE. The FloaTEM system transmits a primary electrical current through a transmitter loop (Tx) wire. This creates a static primary magnetic field. Then, the current in the TX loop is subsequently turned off, resulting in secondary electrical currents being induced in the earth. These induced electrical currents decay with time, and this rate of decay in the secondary electrical field is a function of the bulk conductivity of the subsurface material. As the secondary electrical field decays, a secondary magnetic field is induced and measured at a receiver (Rx) loop towed behind the Tx loop. The Rx loop measures the decay of the secondary magnetic field as a function of time (dB/dt). Measured dB/dt decay curves can be inverted to recover the depth-dependent resistivity structure of the earth. FloaTEM surveys were conducted downstream from Wilmington, DE on 8/26/2020 and 8/27/2020. Data on 2/26/2020 were collected around the Augustine Wildlife Area boat ramp, and data on 8/27/2020 were collected near the Collins Landing boat ramp.

The bulk electrical conductivity of the subsurface was indirectly measured with electromagnetic imaging (EMI) by using induced secondary electromagnetic signals generated by subsurface electrical conductors in response to transmitted electromagnetic energy (Zohdy and others, 1974). Electromagnetic induction data were collected using a DUALEM-421 (DualEM, Inc.) mounted on an inflatable stand-up paddle board about 15 centimeters above the water surface. The DUALEM-421 uses 3 transmitter-receiver coil spacings (4-, 2-, and 1-meters) and 2 orientations (vertical dipole, and horizontal dipole). Larger coil spacings interrogate a larger/deeper sampling volume than smaller coil separations. REFERENCE: U.S. Geological Survey, Techniques of Water-Resources Investigations, Book 2, Chapter D1, Zhody, A. A. R., Eaton , G. P., and Mabey, D. R. https://doi.org/10.3133/twri02D1