Process-based karst modelling to relate hydrodynamic and hydrochemical characteristics to system properties

摘要

More than 30% of Europe's land surface is made up of karst exposures. Insome countries, water from karst aquifers constitutes almost half of thedrinking water supply. Hydrological simulation models can predict thelarge-scale impact of future environmental change on hydrological variables.However, the information needed to obtain model parameters is not availableeverywhere and regionalisation methods have to be applied. The responsivebehaviour of hydrological systems can be quantified by individual metrics,so-called system signatures. This study explores their value fordistinguishing the dominant processes and properties of five different karstsystems in Europe and the Middle East. By defining ten system signaturesderived from hydrodynamic and hydrochemical observations, a process-basedkarst model is applied to the five karst systems. In a stepwise modelevaluation strategy, optimum parameters and their sensitivity are identifiedusing automatic calibration and global variance-based sensitivity analysis.System signatures and sensitive parameters serve as proxies for dominantprocesses, and optimised parameters are used to determine system properties.By sensitivity analysis, the set of system signatures was able todistinguish the karst systems from one another by providing separateinformation about dominant soil, epikarst, and fast and slow groundwaterflow processes. Comparing sensitive parameters to the system signaturesrevealed that annual discharge can serve as a proxy for the recharge area,that the slopes of the high flow parts of the flow duration curves correlatewith the fast flow storage constant, and that the dampening of the isotopicsignal of the rain as well as the medium flow parts of the flow durationcurves have a non-linear relation to the distribution of groundwater storageconstants that represent the variability of groundwater flow dynamics. Ourapproach enabled us to identify dominant processes of the different systemsand provided directions for future large-scale simulation of karst areas topredict the impact of future change on karst water resources.