Geoelectric Characterization of Hyporheic Exchange Flow in the Bedrock‐Lined Streambed of East Fork Poplar Creek, Oak Ridge, Tennessee

A multimethod geoelectric survey was implemented between January and March 2022 along a 220‐m long reach of the bedrock‐lined streambed of East Fork Poplar Creek in Oak Ridge, Tennessee to identify locations of surface‐water and groundwater exchange and characterize the subsurface flow paths that convey water between the stream and flood plain. A waterborne self‐potential (WaSP) survey was completed in January 2022 to measure the electric streaming‐potential field in the stream. Electric resistivity tomography (ERT) was performed in March 2022 on the flood plain adjacent to the WaSP survey reach to map the electric resistivity distribution and characterize the hydrogeology and subsurface flow paths that facilitate surface‐water and groundwater exchange in the bedrock‐lined stream. The combination of WaSP and ERT data support the qualitative interpretation that surface‐water and groundwater exchange likely occurs along fractures in outcropping bedrock and along two fault lines that intersect the limestone creek bed. Plain Language Summary Groundwater flow creates a natural electrical field on the land surface and in streams. Electrical geophysical measurements, measured on the land surface and in streams, measure both the natural electric field attributed to groundwater flow and artificial electric fields that are created by injecting electric current into the Earth. The natural electric field enables scientists to identify locations in bedrock‐lined streambeds where surface‐water flows into the subsurface, or where groundwater in the subsurface discharges into the stream, and the artificial electric fields enable scientists to create images of the electrical properties of the subsurface hydrogeology. This information enables subsurface flow paths to be mapped and characterized and locations where water enters or exits the stream to be identified with greater accuracy. We use geoelectric measurements at East Fork Poplar Creek, Oak Ridge, Tennessee to identify apparent locations where water may flow between the bedrock‐lined streambed and the flood plain. Key Points Waterborne self‐potential and electric resistivity tomography are performed to investigate hyporheic exchange in a bedrock‐lined stream Waterborne self‐potential logging provides an indicator of hyporheic exchange by the polarity of the streaming potential Electric resistivity tomography enables characterization of hyporheic exchange flow paths