Abstract: Geophysical methods have been an important component of effective hydrogeologic investigations overthe Edwards aquifer in central Texas. A variety of electrical and electromagnetic methods have been used to mapstratigraphy and geologic structure and to locate buried sinkholes and caves. Geophysical methods can alsocharacterize faults and fractures in the Balcones Fault Zone (BFZ). Six exemplary case studies across the Edwardsaquifer in the Austin area show that the location of buried caves and sinkholes, and fault characterization are bestaccomplished by using a combination of 2-D and 3-D resistivity imaging and self-potential methods. Additionalgeophysical methods, such as ground penetrating radar, induced polarization, and seismic refraction tomographycan be also used to characterize faults and karstic features. It is noted, however, that successful application of themethods is site dependent; applications in other karstic regions could respond differently to different geophysicalmethods and select  different primary geophysical methods.