An integrated hydrogeological and hydrogeophysical characterization of potential saltwater intrusion pathways in a fractured aquifer
Abstract
Fractures and fracture zones exert strong controls on groundwater flow regimes. Fractures are often more hydraulically conductive than the surrounding host rock; however, not all fractures are open to fluid flow. The hydraulic properties of fractured media differ with fracture aperture, intensity, orientation, connectivity and infill material. The interrelationship of any or all of these factors often causes fractured systems to be hydraulically anisotropic. Moreover, the scale of fracture flow varies from the local scale of individual fractures to the regional fracture zone scale. Characterization of fractured systems is both critical and difficult because flow and transport paths are complex. In this study, 2-D electrical resistivity imaging (ERI), 3-D ERI, fracture mapping and hydrogeological results were integrated to characterize a fracture system on Saturna Island, British Columbia, Canada. Bedrock consists of sandstone-dominant and mudstone-dominant formations with interbedded zones of mudstone and sandstone at formation boundaries. The presence of bedding plane fractures, joints, and faults suggest fracturing at a variety of scales. The geophysical results are consistent with local (outcrop) geology and previous (hydrostratigraphic and hydrostructural) conceptualizations. The images show a distinction between overburden, sandstone-dominant and mudstone-dominant units and the presence of fractured zones. However, discrete fractures were not identified using ERI. Consequently, under some geologic conditions it is possible to use ERI to constrain the aquifer architecture for groundwater models at a regional and sub-regional scale. In this particular fractured setting, ERI may be useful for identifying permeable pathways for saltwater intrusion, which may be associated with fracture zones.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSMNS41A..01R
- Keywords:
-
- 1800 HYDROLOGY;
- 1829 Groundwater hydrology;
- 8010 Fractures and faults