Karst conduit size distribution evolution using speleogenesis modelling

Abstract

Abstract One of the critical aspects when modeling groundwater flow in karstic aquifers is to estimate the statistics of the size of the conduits, in conjunction with the connectivity of the karst conduit network. Statistical analysis can be performed on data gathered by speleologists, but a significant fraction of the karst conduit networks is not directly reachable, and therefore, the resulting statistics are incomplete. An alternative method to evaluate the inaccessible areas of a karst conduit network is to simulate numerically the speleogenesis processes. In this paper, we use a coupled reactive-transport model to simulate the evolution of a vertical section of a fractured carbonate aquifer and investigate how the statistical distribution of the fracture apertures evolves. The numerical results confirm that the karstification proceeds in different phases that were previously hypothesized and described (inception, gestation, development). These phases result in a multi-modal distribution of conduit aperture. Each mode has a roughly lognormal distribution and corresponds to a different phase of this evolution. These outcomes can help better characterize the statistical distribution of karst conduit apertures including the inaccessible part of the network.