Poster Number 236
See more from this Division: Topical Sessions
See more from this Session: Innovative Methods for Investigating Flow and Transport in Karst Systems (Posters)
Abstract:
The Edwards karst aquifer in south-central Texas is recharged primarily from losing streams and secondarily from infiltration of water across upland interstream areas. The study area was in Edwards limestone overlying Headquarters Cave in an upland interstream setting in northwest San Antonio, Texas. Time-series resistivity involved repeated surveys over a 10 month period using a 48-electrode dipole-dipole array with 1-m electrode spacing. The two dimensional vertical pseudosection was discretized into specific sampling volumes for which resistivity was repeatedly measured. Temporal variance of resistivity was calculated for each sampling volume. Highest resistivity variance was in the uppermost 0.5-m depth, reflecting wetting and drying of surficial soil. Large variations in resistivity were also mappable along subvertical linear zones and in discrete horizons reflecting vertical and bedding-plane conduits within the epikarst. Additional work is needed to quantify water storage and flux in the unsaturated limestone for better calibration with electrical resistivity.
See more from this Division: Topical Sessions
See more from this Session: Innovative Methods for Investigating Flow and Transport in Karst Systems (Posters)