1 U.S. Department of the Interior U.S. Geological Survey Using Geophysical Methods to Characterize the Hydrostatigraphy of the Edwards Aquifer By Jason D. Payne 1, Bruce D. Smith 2, Sachin D. Shah 3, and Allan K. Clark 4 Texas Water Science Center, San Angelo, Tx 1 Crustal Imaging Characterization Team, Denver, Co 2 Texas Water Science Center, Austin, Texas, Tx 3 Texas Water Science Center, San Antonio, Tx 4

Geophysical Data Collection in the Edwards Aquifer Well Logging, Greg Stanton, WRDHEM data collection, GD GEM-2 data collection, Bruce Smith, GD TDEM data collection, Brian Imig, WRD GPR data collection, Jim Stefanov, Jason Payne, Brian Imig, Ryan Thompkins, WRD Magnetometer, Jason Payne, WRD, Dave Smith, GD

Edwards Aquifer Geophysical Publications  Geologic Discipline Seco Creek HEM Seco Creek HEM Bexar County HEM Bexar County HEM Medina And Uvalde County Aeromagnetic Survey Medina And Uvalde County Aeromagnetic Survey  Water Resources Discipline Travis and Hays Counties TDEM survey Travis and Hays Counties TDEM survey  WRD and GD Combined Bexar County Cibolo Canyon survey Bexar County Cibolo Canyon survey

Geophysics in the Edwards Aquifer  Geologic Discipline Program Research Program Research Regional Studies Regional Studies Entire Edwards AquiferEntire Edwards Aquifer Mostly federal funding Mostly federal funding  Water Resources Discipline Site Research Focused Study Areas Problem specific Funded by local cooperators

Areas of Specialization  Geologic Discipline 1. Interpretation 2. Data Analysis 3. Data Collection 4. Geologic Models  Water Resources Discipline 1. Data Collection 2. Data Analysis 3. Interpretation 4. Hydrologic Models

Common Science Objectives  Utilize site information in regional programs (Edwards – Trinity Aquifers)  Develop integrated hydrologic and geologic models  Improve hydrostratigraphic understanding of geologic and hydrologic mapping methods  Contribute to scientific reports and investigations

Geophysical Studies throughout the Edwards Aquifer

HEM Surveys – GD 8 Seco Creek HEM survey Bexar County HEM survey

Cibolo Canyon Data Collection – WRD and GD

GeologicMapping RevisedGeologicMap Methods used for integrated study Geophysical data collection Geophysical analysis

Direct-Current Resistivity Dolomiticmember zone of intense fracturing

Time-Domain EM Data Analysis

Hydrostratigraphic Model Edwards aquifer unit Hydrologic characterization Generalized resistivity range Cyclic and Marine high permeability, local low permeability mudstone Moderate Leached and collapsed high permeability High Regional dense low permeability, barrier to vertical flow Low Below 100 Grainstone generally low permeability, local high permeability in conduits and fractures Moderate Kirschberg evaporite moderate permeability High Dolomitic high permeability associated with fractures and caves Very high Above 500 Basal nodular generally low permeability, local high permeability in conduits and fractures Low Below 100

Common Science Objectives  Utilize site information in regional programs (Edwards – Trinity Aquifers)  Develop integrated hydrologic and geologic models  Develop hydrostratigraphic concepts to improve geologic and hydrologic mapping and modeling  Contribute to joint scientific reports and data bases (DAPLE GOOGLE EARTH)

Resources  Shah, S.D., Smith, B.D., Clark, A.K., and Payne, J.D., 2008, An integrated hydrogeologic and geophysical investigation to characterize the hydrostratigraphy of the Edwards aquifer in an area of northeastern Bexar County, Texas: U.S. Geological Survey Scientific Investigations Report 2008–  This and other Texas Water Science Center Publications can be downloaded at the following URL: