Characterization and Assessment of Groundwater Resources in a Complex Hydrological Basin of Central Greece (Kopaida basin) with the Joint Use of Hydrogeochemical Analysis, Multivariate Statistics and Stable Isotopes

Abstract

Combined assessments from different methodologies, including hydrogeochemical analysis, multivariate statistics and stable isotopes, were used in order to characterize the groundwater resources of a heterogeneous aquifer system in central Greece and to evaluate the overall environmental regime. Results outlined the driving factors that chiefly control groundwater chemistry and delineated the major pathways of groundwater flow. Following the results of the combined assessments, hydrogeochemistry is influenced both by geogenic and anthropogenic factors including the geological substrate, intense agricultural activities and ongoing geochemical processes which impact the concentrations of redox sensitive agents like NO₃, Fe, Mn and SO₄. Stable isotope evaluations supplemented the above assessments by providing critical information for the hydrodynamics of the heterogeneous aquifer system. Evaporation is the main factor influencing the isotopic composition of water resources, in addition to the slow percolation rates of the thick unsaturated zone. Comparisons between δ ¹⁸Ο and δD values for surface and groundwater samples revealed an interaction among water systems through the developed karstic network and/or the riverbeds of higher permeabilities. Eventually, the integrated conceptual approach of diverse methodologies was applied successfully for the identification of hydrogeological and hydrogeochemical assessments in the case of Kopaida basin; evaluations were cross-confirmed and supplemented when needed, hence providing essential information for strategic planning and water resources management.