A conceptual model of epikarst processes across sites, seasons, and storm events

Abstract

The epikarst is an area of complex interactions and processes and is an important component of the critical zone. Understanding how processes in the epikarst are similar and different between sites is of the utmost importance in determining how information about these systems can be used to understand broader concepts and implications in the unsaturated zone of karst systems. We looked at two sites in separate karst regions of Kentucky, USA, to assess patterns in storm response of epikarst systems. Using discharge and analytes including pH, temperature, specific conductance, and turbidity as markers of epikarst processes, we assessed how each of these parameters responded to storm pulses, comparing between sites and seasons (leaf-on vs. leaf-off). Our results show that hysteresis patterns vary between analyte and season, but there are consistent patterns between sites. Regression modeling of cross-correlation results show that storm intensity drives the timing of storm responses, whereas precipitation total drives how strongly the analytes correlate to discharge response. Across both sites, analytes respond similarly, with the lag in response likely tied to the size of the basin. The similarity in response of the study sites suggests that the processes controlling transport through the epikarst are consistent across sites. The influence of a storm event and season on these responses highlight the importance of further study of soil and near-surface processes on controlling geochemical responses in the epikarst.