Numerical modeling of flow and transport in the Bari industrial area by means of rough walled parallel plate and random walk models

Modeling fluid flow and solute transport dynamics in fractured karst aquifers is one of the most challenging tasks in hydrogeology. The present study investigates the hotspots of groundwater contamination in the industrial area of Modugno (Bari southern Italy), where the limestone aquifer has a fractured and karstic nature. A rough walled parallel plate model coupled with a geostatistical analysis to infer the values of the equivalent aperture has been implemented and calibrated on the basis of piezometric data. Using the random walk theory, the steady-state distribution of hypothetical contamination with the source at the hotspot has been carried out, reproducing a pollution scenario which is compatible with the observed one. From an analysis of the flow and transport pattern it is possible to infer that the anticline affecting the Calcare di Bari formation in direction ENE-WSW influences the direction of flow as well as the propagation of the contaminant. The results also show that the presence of nonlinear flow influences advection, in that it leads to a delay in solute transport with respect to the linear flow assumption. This is due to the non-constant distribution of solutes according to different pathways for fractured media which is related to the flow rate.