Generation of complex karstic conduit networks with a hydrochemical model

In this paper, we present a hydrochemical model that can be used to generate plausible karstic conduit networks that honor what is known about geology, hydrology, and topography of a karst system. To make the model applicable to a range of natural karst systems, we introduce a flexible and physically realistic flow boundary condition along the land surface. Moreover, whereas comparable existing speleogenesis models use an explicit reactive‐transport scheme, we propose an implicit reactive‐transport scheme to permit a coarser spatial discretization of the conduit cells. An application to a real karst system illustrates that the model can generate a realistic karstic network that reproduces observed hydrologic behavior in terms of current spring flow rates, regional hydraulic head field as well as average groundwater residence times. Our model provides a useful tool to generate ensembles of possible karstic conduit networks that may be used within a stochastic framework to analyze flow and transport prediction uncertainty associated with a lack of knowledge about network geometry. Key Points A speleogenesis model is presented that can be used to generate conduit networks at a regional scale Our model accounts for a switch between hydraulic and catchment control and uses an implicit reactive‐transport scheme The model is applied to a real system and it is illustrated that the model can generate a realistic conduit network