Assessing Streamflow Sensitivity to Precipitation Variability in Karst‐Influenced Catchments With Unclosed Water Balances

Abstract

AbstractKarst 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 absence is due to difficulties of properly considering the strong differences of karstic and nonkarstic hydrodynamics and the widespread occurrence of unclosed water balances in karstic regions due to intercatchment groundwater flow (IGF). In this study, we present a new approach that uses hydrological signatures to identify important natural processes and appropriate model structures for the simulation of karst‐influenced catchments. We account for karstic IGF and apply our approach to six karst‐influenced catchments in Europe and the Middle East. We estimate the contributions of karstic and nonkarstic parts to the total streamflow sensitivity. With different model structures identified at different sites, our approach reduces water balance errors by 18% and reduces the root mean squared error by 20% for catchments where the IGF is deemed important. We find that IGF modifies the contribution of karstic areas to the total streamflow sensitivity. The total streamflow sensitivity increases under gaining conditions and decreases under losing conditions for catchments with larger karstic discharge elasticity, while it shows the converse change for catchments with smaller karstic discharge elasticity. Modeling streamflow at karst‐influenced catchments requires the consideration of differences between karstic and nonkarstic areas, and the IGF matters for catchments with unclosed water balances.