Estimating the Distribution of Hydraulic Properties Using Resistivity Models Derived from Airborne Geophysics

Monday, December 4, 2017: 10:30 a.m.
Andrew Genco , XRIBlue, Denver, CO
Kristen Pierce , XRIBlue, Denver, CO
Rachel Woolf , XRIBlue, Denver, CO

The Ramotswa transboundary aquifer is shared between South Africa and Botswana. An extended drought throughout the region has increased the need to understand this shared water resource. An airborne electromagnetic (AEM) survey was conducted to generate new information about the aquifer in order to support water security and facilitate its sustainable management between the two countries. Using the AEM survey results, the three-dimensional spatial distribution of the dolomite aquifer was interpreted and estimates of the aquifer’s distribution and range of porosity and hydraulic conductivity were made. Porosities throughout the dolomite were estimated using a modified version or Archie’s Law specific to carbonates. Transmissivity values were previously calculated in the Ramotswa Well Field, from both constant rate and step pumping tests, and were used in conjunction with resistivity data, extrapolated over the well field, to calculate the relationship between hydraulic conductivity and resistivity for the aquifer. Minimal hydraulic data was collected on the ground within the study area, presenting a challenge for relating the electrical resistivity data to hydraulic properties, especially over a large and heterogeneous aquifer. The distribution of hydraulic conductivity in the aquifer was geoelectrically estimated using a generalized log-log linear electrical-hydraulic correlation function, the slope of which is dependent on the geologic and geochemical environment.
Andrew Genco, XRIBlue, Denver, CO
Andrew has been a geophysicist with XRIBlue since January 2014, where he has focused on using the airborne EM method for water resource mapping and management projects. Prior to joining XRIBlue, Andrew was a geophysicist with Zonge and hydroGEOPHYSICS Inc, where he worked on and managed a variety of environmental and engineering geophysics projects. Andrew obtained his BS in Geology from Lafayette College in 2006, and MS in Geophysics from Colorado State University in 2013.


Kristen Pierce, XRIBlue, Denver, CO
Kristen Pierce is a geophysicist with experience in both ground based and airborne methods applied to exploration of water resources. Kristen earned her BS in geophysical engineering at the Colorado School of Mines. At XRIBlue Kristen specializes in data integration, interpretation and analysis to generate subsurface geologic and hydrologic models. Before joining XRIBlue, Kristen worked for the United States Bureau of Reclamation, utilizing geophysics for geotechnical engineering projects.


Rachel Woolf, XRIBlue, Denver, CO
Rachel has been in the geophysical field since obtaining her bachelor's degree from the Colorado School of Mines (CSM) in 2002. Working primarily in near surface geophysics, Rachel has experience in numerous disciplines including unexplored ordnance detection. She obtained her Master's degree, also from CSM, in 2013 with an emphasis in groundwater and geothermal studies. She has been working in groundwater exploration for XRI Blue and its sister companies since 2010, specializing in airborne electromagnetic data processing and inversion.


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