Multiscale understanding of fluid flow and solute transport in karst systems: insights from laboratory experiments, field studies, and numerical modeling

Abstract

Understanding the influence of triple-porosity structures (simultaneous presence of the porous matrix, fractures, and conduits) in karst aquifers is critical for predictive modeling of contaminant transport in these highly heterogeneous systems. As climate change intensifies precipitation variability in the Upper Midwest, improving our ability to model groundwater response to recharge fluctuations is essential for protecting future water resources. Here, we combined laboratory experiments, field investigations, and numerical modeling to comprehensively explore these processes. Laboratory core flooding experiments were conducted using dolostone core triple-porosity analogues. Both passive solute and reactive transport experiments under inertial and non-inertial laminar flow conditions were conducted to assess solute exchange and plume evolution. Complementing these controlled studies, field-scale insights were from a karst aquifer site, where a two-dimensional groundwater model was calibrated against spring discharge records and groundwater elevation data. We outline how changes in recharge and flow rate alter discharge and breakthrough curve development.