Abstract
In three-dimensional (3-D) implicit geological modeling, the bounding surfaces between geological units are automatically constructed from lithological contact data (position and orientation) and the location and orientation of potential faults. This approach was applied to conceptualize a karst aquifer in the Middle Triassic Muschelkalk Formation in southwest Germany, using digital elevation data, geological maps, borehole logs, and geological interpretation. Dip and strike measurements as well as soil-gas surveys of mantel-borne CO2 were conducted to verify the existence of an unmapped fault. Implicit geological modeling allowed the straightforward assessment of the geological framework and rapid updates with incoming data. Simultaneous 3-D visualizations of the sedimentary units, tectonic features, hydraulic heads, and tracer tests provided insights into the karst-system hydraulics and helped guide the formulation of the conceptual hydrogeological model. The 3-D geological model was automatically translated into a numerical single-continuum steady-state groundwater model that was calibrated to match measured hydraulic heads, spring discharge rates, and flow directions observed in tracer tests. This was possible only by introducing discrete karst conduits, which were implemented as high-conductivity features in the numerical model. The numerical groundwater flow model was applied to initially assess the risk from limestone quarrying to local water supply wells with the help of particle tracking.
Highlights
Understanding the geology is the backbone of any groundwater management project, since hydraulic heads and velocities, as well as flow trajectories and residence times, are strongly controlled by the properties and arrangement of lithological entities
Describing karst aquifers for the purpose of quantifying groundwater flow poses unique challenges due to the complex and highly uncertain arrangement of karst conduits where water flow often occurs under turbulent conditions at very high velocities (e.g., Jeannin 2001)
To obtain an appropriate hydrogeological conceptual model of a karst aquifer, information on structural geology necessarily needs to be complemented by field observations and surveys such as tracer tests (e.g., Perrin and Luetscher 2008)
Summary
Understanding the geology is the backbone of any groundwater management project, since hydraulic heads and velocities, as well as flow trajectories and residence times, are strongly controlled by the properties and arrangement of lithological entities. This paper demonstrates how a spatially distributed model can be conceptualized, set up, and calibrated to describe groundwater flow in a karst aquifer by combining field surveys, 3-D implicit geological modeling, and an iterative model calibration method to reasonably consider hydraulically relevant karst conduits in the model.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
