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

Groundwater discharge points to coastal waters can be identified and quantified using natural electrical and temperature data. In August 2022, U.S. Geological Survey (USGS) collected water-borne electromagnetic induction and temperature along selected transects within Hen Cove on Cape Cod, Massachusetts, following a spatial survey of bed sediment temperature. Handheld thermal infrared data were also collected to locate areas of focused terrestrial groundwater discharge based on characteristic cool temperatures of groundwater in late summer. Those initial datasets guided the installation of vertical bed sediment temperature profilers, water pressure loggers suspended in piezometers, and the collection of pore water samples. The individual datasets from this study are described in more detail under the Child Items of this data release, organized by data type.

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).

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 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 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 electrical resistivity tomography (ERT) and frequency domain electromagnetic (FDEM) data collected in areas of unwalled shoreline at the Bremerton Naval Complex, WA, June 1-5, 2023. Preliminary inverse results from the FDEM data area also included. Two sites were investigated: Charleston Beach and Segment 4. Charleston Beach is a gently sloping pebble beach adjacent to the naval complex; whereas Segment 4 is a steeply sloping section of rocky shoreline on the naval complex surrounded by a pier and naval complex infrastructure. At Charleston Beach, FDEM data were collected with two different instruments with different sensitivity patterns (a DualEM-421 and a GEM-2) during negative tide (less than the mean low tide level) on June 2,2023. At Segment 4, various time-lapse ERT configurations were tested during June 3-5 over tidal cycles, while FDEM datasets (GEM-2 only) were collected during negative tides over this period. To facilitate comparison of geophysical data with tides, tide elevation predictions from NOAA station 9445958 are included in this release. A local digital elevation model was also created for Segment 4 using a real time kinematic (RTK) global positioning system.

This data release contains electrical resistivity tomography (ERT) and frequency domain electromagnetic (FDEM) data collected in areas of unwalled shoreline at the Bremerton Naval Complex, WA, June 1-5, 2023. Preliminary inverse results from the FDEM data area also included. Two sites were investigated: Charleston Beach and Segment 4. Charleston Beach is a gently sloping pebble beach adjacent to the naval complex; whereas Segment 4 is a steeply sloping section of rocky shoreline on the naval complex surrounded by a pier and naval complex infrastructure. At Charleston Beach, FDEM data were collected with two different instruments with different sensitivity patterns (a DualEM-421 and a GEM-2) during negative tide (less than the mean low tide level) on June 2,2023. At Segment 4, various time-lapse ERT configurations were tested during June 3-5 over tidal cycles, while FDEM datasets (GEM-2 only) were collected during negative tides over this period. To facilitate comparison of geophysical data with tides, tide elevation predictions from NOAA station 9445958 are included in this release. A local digital elevation model was also created for Segment 4 using a real time kinematic (RTK) global positioning system.

This data release provides saturated sediment temperatures from vertical temperature profilers, pressure head data from co-located pizometers, and estimates of 1D groundwater flux using a recursive-estimation framework to infer groundwater/surface-water exchange based on the collected temperature time-series (approximate 1,6,16,26cm depths, AlphaMachX vertical temperature profilers) from below the sediment/water interface. A heat-transport problem was formulated as a state-space model (SSM), in which the spatial derivatives in the convection/conduction equation are approximated using finite differences. The SSM is calibrated to estimate time-varying specific discharge using the Extended Kalman Filter (EKF) and Extended Rauch-Tung-Striebel Smoother (ERTSS) algorithms. These algorithms are described in McAliley et al., 2024 (https://doi.org/10.1029/2021WR030443) and relevant algorithm has been publicly released previously on ScienceBase (https://doi.org/10.5066/P99DBTKT). This data release contains 3 zipped folders, EKF_ERTSS_results.zip that contains EKF and ERTSS groundwater flux estimates, Temperature_observations.zip that contains raw observed temperature time series, and Pressure_data.zip that contains raw observations of pressure from piezometers adjacent to vertical temperature profilers. Additionally, water pressure transducers (Onset HOBO model U20L) were suspended at two depths within 2" steel pipes with 20cm screen drivepoints that were driven vertically into bed sediments adjacent to locations TX129 and TX132.