Detection and quantification of preferential flow using artificial rainfall with multiple experimental approaches

Preferential flow in the unsaturated zone strongly influences important hydrologic processes, such as infiltration, contaminanttransport, and aquifer recharge. Because it entails various combinations of physical processes arising from the interactions ofwater, air, and solid particles in a porous medium, preferential flow is highly complex. Major research is needed to improve theability to understand, quantify, model, and predict preferential flow. Toward a solution, a combination of diverse experimentalmeasurements at multiple scales, from laboratory scale to mesoscale, has been implemented to detect and quantify preferentialpaths in carbonate and karstic unsaturated zones. This involves integration of information from (1) core samples, by meansof mercury intrusion porosimeter, evaporation, quasi-steady centrifuge and dewpoint potentiometer laboratory methods, toinvestigate the effect of pore-size distribution on hydraulic characteristics and the potential activation of preferential flow,(2) field plot experiments with artificial sprinkling, to visualize preferential pathways related to secondary porosity, throughuse of geophysical measurements, and (3) mesoscale evaluation of field data through episodic master recession modelingof episodic recharge. This study demonstrates that preferential flow processes operate from core scale to two different fieldscales and impact on the qualitative and quantitative groundwater status, by entailing fast flow with subsequent effects onrecharge rate and contaminant mobilizing. The presented results represent a rare example of preferential flow detection andnumerical modeling by reducing underestimation of the recharge and contamination risks.