Hydrogeological Investigation of a Karst Aquifer System

Abstract

This study aims to present the hydrogeological and hydrochemical characteristics of Paradisos Karst aquifer system (PAS), Northeast Greece. The average area of the PAS is estimated according to Thornthwaite and Mather (1957) (T-M) procedure at 74.2 km2. The karst system, which is largely fault-controlled, discharges through three permanent karst springs: KS15, KS20 and KS21. The average discharge rate was calculated for two of them at 0.726 m3/s. The time series analysis shows that: (a) the memory effect for the PAS is extremely high; and (b) the karst system is a poorly developed with high storage capacity and absence of a quick flow component. The chemical type for the majority of the groundwater samples is of Ca-HCO3 type. The chemical properties of the groundwaters are strongly influenced by alkaline earth metals and weak acids. The presence (sporadically) of high NH4 + content and slightly increased nitrate, ammonium and phosphate values in springs KS20 and KS21 is attributed to the presence of anthropogenic sources, especially septic tanks and agriculture. All studied groundwaters are oversaturated in calcite and aragonite, which suggests a mechanism of diffuse flow. The morphology and geology of the PAS catchment area, and data from hydrographs and chemographs, show that the hydrologic system is dominantly of diffuse flow. The use of time series analysis combined with classic hydrogeological techniques (i.e., degree of karstification, T-M procedure, chemographs and saturation indices) can be used in order to successfully characterize a karst system and achieve a sustainable integrated water management in it.