Validation of Vulnerability Assessment Using Time Series Analysis—the Case of the Korentan Spring, SW Slovenia

Abstract

In the shallow Orehek karst aquifer in southwest Slovenia, the use of hydrological data analysis for the purpose of validating the assessment of water source vulnerability was tested. The appropriate criteria for the aquifer and groundwater flow characterization were identified and major drawbacks highlighted. Results of water budget calculations were used to determine the extent of the catchment of the Korentan spring, which is the main outflow from the aquifer. The vulnerability assessment was verified by autocorrelation and cross-correlation analyses of available daily hydrological time series data. The small variability of the Korentan spring water temperature and electric conductivity time series points to the dominance of autogenic recharge and that sinking streams in the catchment contribute to the spring to a minor degree. The analysis indicated relatively small storage capacity of the aquifer and its high degree of karstification and rapid groundwater flow. The results justify the small proportion of highly vulnerable areas and lower vulnerability for marginal parts of the aquifer. Time series analyses proved to be time- and cost-effective, but have limited applicability for vulnerability validation purposes, as they do not provide direct and clear spatially resolved information on the vulnerability of the catchment.