SELF-POTENTIAL AND ELECTRIC RESISTIVITY TOMOGRAPHY DATA PERTAINING TO GROUNDWATER FLOW FOR THERMAL SPRINGS, HOT SPRINGS NATIONAL PARK, ARKANSAS

Abstract

This study aims to identify groundwater flow pathways and potential geothermal fluid discharge zones in the Hot Springs National Park, Arkansas, through the integration of the Self-Potential (SP) and Electrical Resistivity Tomography (ERT) methods. The dataset, obtained from the United States Geological Survey (USGS), includes both ERT and SP measurements within the study area. The ERT survey was conducted along two profiles using a dipole–dipole configuration with 48 electrodes and a 1-meter electrode spacing. The SP dataset consists of a spatial contour map of natural potential values and time-lapse monitoring measurements conducted over an 11-month period (February 2023–January 2024). Inversion results from the ERT reveal a resistive layer at shallow depths (>147 Ω·m), interpreted as massive or dry rock, an underlying conductive layer (14–30 Ω·m) associated with fluid-saturated zones, and a transitional layer in between. The SP contour map shows positive anomalies of up to +35 mV, indicating discharge zones, and negative anomalies below -65 mV, representing recharge zones. Time-lapse SP analysis at 40 surface points indicates fluctuations in potential values that correlate with seasonal variations and the dynamics of groundwater flow. The integration of these analyses confirms that the area surrounding the spring box serves as a primary discharge pathway for hot water from the hydrothermal system, with fluid movement controlled by local lithology and geological structures.