Influence of conduit network geometry on solute transport in karst aquifers with a permeable matrix

In karst aquifers with significant matrix permeability, water and solutes are exchanged between the conduits and carbonate matrix. Transport through the matrix increases the spread of solutes and increases travel times. This study numerically evaluates advective solute transport in synthetic karst systems that contain 3D branching conduit networks. Particle tracking is performed to analyze the spatial and temporal transport history of solute that arrives at the conduit outlet. Three measures of transport connectivity are used to quantify the solute migration behavior: the skewness of the particle arrival time distribution, the normalized fifth percentile of arrival times, and the fraction of the total travel time that occurs within conduits. All three of these metrics capture the influence of conduit network geometry on solute transport. A more tortuous network leads to enhanced conduit-matrix mixing, which reduces the transport connectivity and yields a broader distribution of solute arrival times. These results demonstrate that the conduit network geometry is an important control on solute transport in karst systems with a permeable matrix.

► Percolation algorithm used to generate 3D karstic conduit networks.
► Numerical study of solute advection in synthetic aquifers with embedded networks.
► Permeable matrix allows solute exchange between conduits and matrix.
► Degree of conduit-matrix mixing depends on geometry of the conduit network.
► Greater network tortuosity produces a reduction in transport connectivity.