Tracking changes in bulk electrical conductivity (EC) during tracer tests in saturated sediments allows for direct observation of both mobile and less-mobile pore space exchange dynamics. Electrode arrays made up of four stainless steel rods (insulated with the exception of exposed 0.5 cm tips) were installed vertically at depths of interest and apparent electrical resistivity data (the inverse of bulk EC) were collected using a Wenner configuration with an AGI SuperSting R8 meter. The Bulk EC data are described and listed within the files below. Controlled, downward flow experiments were conducted in Dual-domain porosity apparatus (DDPA). Downward flow rates ranged from 1.2 to 1.4 m/d in DDPA1 and at 1 m/d, 3 m/d, 5 m/d, 0.9 m/d as described in the publication: Briggs, M.A., Day-Lewis, F.D., Dehkordy, F.M.P., Hampton, T., Zarnetske, J.P., Singha, K., Harvey, J.W. and Lane, J.W., 2018, Direct observations of hydrologic exchange occurring with less-mobile porosity and the development of anoxic microzones in sandy lakebed sediments, Water Resources Research, DOI:10.1029/2018WR022823.

Quantification of mobile/less-mobile porosity dynamics at the sediment/water interface is critical to predicting contaminant storage, release, and transformation processes. Zones in groundwater flow-through lakes where lake water recharges the aquifer can strongly control aquifer water quality. Less-mobile porosity has previously been characterized in aquifers using flow path scale (10's of m+) tracer injections which are analyzed using numerical models. Methodology was recently developed to couple geoelectric measurements (bulk electrical conductivity, EC), which are directly sensitive to less-mobile ionic tracer exchange processes, with pumped fluid EC tracer data over time. If the fluid EC concentration history is assumed to reflect the more mobile porosity exchange processes, these paired fluid and bulk EC measurements can be used to quantify less-mobile porosity exchange in discrete cm-scale packets of sediment at the interface between surface and groundwater. For this study, tracer experiments were conducted in multiple rate-controlled downward flow experiments over several days. Although the bed was composed predominantly of highly permeable sands and gravels, which is not an intuitive sediment texture for less-mobile porosity, embedded cobbles created areas of less-mobile flow zones proximal to large cobbles. These experimental findings are described in detail in the associated publication: Briggs, M.A., Day-Lewis, F.D., Dehkordy, F.M.P., Hampton, T., Zarnetske, J.P., Singha, K., Harvey, J.W. and Lane, J.W.(2018), Direct observations of hydrologic exchange occurring with less-mobile porosity and the development of anoxic microzones in sandy lakebed sediments, Water Resources Research, DOI:10.1029/2018WR022823.

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 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 dataset was generated during the precision testing of three water-quality sondes before picking one to use for field deployment of high frequency ground-water quality monitoring. Precision is important because the authors wanted to try and minimize calibration drift corrections between site visits. A laboratory experiment was conducted for the three sondes to simultaneously measure at hourly intervals with a setup of standard solution circulating past the sondes to simulate field conditions. The electrical conductivity experiment lasted 33 hours, the pH experiment lasted 13 hours, and the DO experiment failed (no data).

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 main Delaware River channel and the Leipsic River. The Leipsic River flows through an estuary into the Delaware Bay. Subsurface conductive zones, when viewed in the context of the regional conceptual model and other data, can help determine the likely groundwater location of the freshwater/saltwater interface within the Delaware River, as well as key hydrogeological layers such as the Lower Potomac-Raritan-Magothy Aquifer within the Northern Atlantic Coastal Plain Aquifer System, and their connectivity with the riverbed. Permeable aquifers could provide a hydraulic connection between surface water and inland groundwater. Therefore, changes to river water salinity could have an accelerated impact on water pumped from wells inland that are connected via these permeable aquifers. 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 from 8/26/2020 were collected around the Augustine Wildlife Area boat ramp, and data on 8/27/2020 were collected near the Collins Landing boat ramp. FloaTEM surveys were again conducted downstream from Wilmington, DE on 8/25/2021 and 8/26/2021. Data from 8/25/2021 were collected upstream of the 2020 surveys around the Pennsville public boat ramp, while data on 8/26/2021 were collected near the Collins Landing boat ramp and covered a similar area as the 2020 data. Data collected in 2021 also included a section of the Delaware River further upstream near Philadelphia PA, collected on 8/24/2021 and made use of the Fort Mifflin boat ramp. A final back and forth profile in the Leipsic River within the Bombay Hook National Wildlife Refuge (estuary) was gathered on 8/27/21, and used the Port Mahon Boat Launch as the starting/ending point. Surface water specific conductance data were also collected during portions of the surveys.

In June 2017, U.S. Geological Survey (USGS) collected geophysical measurements to help map variations in electrical properties to infer shallow flowpaths and storage zones influenced by residual spilled unconventional oil and gas (UOG). Two survey profiles were collected, each including dipole-dipole and Wenner-Schlumberger configurations. For each survey a total of 56 electrodes spaced 1.0 meter (m) apart were used. During the ERT measurement, current is injected through two current electrodes and voltage is measured sequentially across multiple pairs of potential electrodes; the known current and the measured voltages are used to determine the apparent resistivity of the subsurface. Inverse modeling of ERT survey results provide profiles of resistivity that can be interpreted for subsurface layers. This data release provides the raw ERT data and output from inversion.

The U.S. Geological Survey (USGS) and the National Park Service (NPS) have collaborated on monitoring the chloride flux in the major rivers of Yellowstone National Park by periodically sampling the rivers and analyzing chloride concentrations in discrete water samples since the 1970's. However, restrictions of winter travel, great distances between sites, and sampling and analytical costs have limited collection to approximately 28 samples per site annually. Electrical conductivity data can be used as a proxy for chloride concentrations in many of the major rivers of Yellowstone National Park. Electrical conductivity is a measure of the ability of water to pass an electrical current, and it is affected by the presence of inorganic ions such as chloride and other geothermal solutes. In 2012, an electrical conductivity probe was installed in the Snake River above Jackson Lake near Flagg Ranch. Continuous (every 15 minutes) electrical conductivity measurements provide high-resolution data that can be used to rapidly calculate chloride flux in the Snake River.

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 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.