A hydraulic–hydrochemical approach to impact assessment of a grout curtain on karst aquifer behavior

Combining the results obtained by hydraulic (hysteresis) and hydrochemical (multivariate statistical analysis) approaches gives a better understanding of karst aquifer behavior, functioning of the hydraulic barrier and hydrogeochemical processes. The hydraulic approach is based on the principle that the relation of the groundwater levels in piezometers and the water level in a surface-water reservoir often follow certain hysteretic patterns that reflect a system of internal structure. This allows an analysis of the structure of the karst system as well as properties or functionality of the hydraulic barrier associated with the dam. Adequate understanding of the hysteresis diagrams is crucial to successfully addressing the issue of karst aquifer behavior and water leakage direction; normalized hysteresis data provided easier comparison between the data series and the interconnections among observed patterns. The application of the hydrochemical approach further contributed to an understanding of the karst system as well as the impact of the hydraulic barrier. Two-way hierarchical cluster analysis enabled the isolation of areas with similar hydrochemical characteristics, which was supplemented with circulation directions assumed by hydraulic methods. Factor analysis helped in identifying major hydrogeochemical processes in the various hydraulic regimes. The combined findings of hydraulic and hydrochemical approaches were successfully applied to a complex karst aquifer system where the reservoir (Lazići) was created for a reversible hydropower plant, situated in the Tara mountains, in the Dinaric karst of western Serbia.