Yan Liu , Thorsten Wagener, Andreas Hartmann 

Karst hydrological models are widely used for simulating groundwater dynamics at the aquifer scale. However, modeling streamflow of a topographic catchment that is partially covered by karst is rarely reported. This is due to difficulties of properly considering the strong differences of karstic and non-karstic hydrodynamics and the widespread occurrence of unclosed water balances in karstic regions caused by inter-catchment groundwater flow. In this study, we present a new approach that uses hydrologic signatures to identify important processes and appropriate model structures for the simulation of karst-influenced catchments. We include a new method that accounts for karstic inter-catchment groundwater flow. We apply our approach to six karst-influenced test catchments in Europe and Middle East. We estimate the contributions of karstic and non-karstic parts to total streamflow sensitivity. With different model structures identified at different sites, our simulation approach provides acceptable simulations especially at those catchments where inter-catchment groundwater flow is deemed important. Using the models to calculate the streamflow sensitivity to precipitation variability, we find that inter-catchment groundwater flow reduces the contribution of karstic area to the total streamflow sensitivity for the losing catchments, while increases that for the gaining catchments. Modeling streamflow at karst-influenced catchments requires the consideration of differences between karst and non-karst, and inter-catchment groundwater flow matters for catchments with unclosed water balance.