Methodological approach for investigation in Karst Hydrogeology

Abstract

It is established that karst aquifers constitutes around 12% of Earth surface and their resources are used for water supply 20-25% of world population, which justifies the global relevance of this type of aquifers. They are abundant in Mediterranean countries where their groundwater has been used along the history by all cultures and civilizations. In spite of the importance and the long history of use by the humanity, the major advances on Karst Hydrogeology occurred after middle 20th century, on the basis of the predominantly geomorphological knowledge acquired in the previous century. The main reason for that was probably the complexity of karst system, its heterogeneity in the distribution of hydraulic properties (porosity and hydraulic conductivity), the different modalities of recharge (autogenic or allogenic; concentrated and diffuse) and the diversity of flow conditions from diffuse flow to conduit flow behavior. This diversity of conditions implies that methodologies of classical hydrogeology can be not directly applied to karst aquifers, and consequently techniques have been adapted or specially developed to investigate karst systems, starting from the always fundamental geological, geomorphological and hydrogeological background. Hydrodynamic analysis (mainly spring hydrograph) inform about the changes in volume of water recharging and discharging the systems and how rapid these occur, but not about the transit or residence times and processes occurring. These aspects can be inferred from the hydrochemistry, considered as hydrodynamic interpretation of chemical composition of groundwater. Besides, natural hydrochemical tracers as total organic carbon and natural fluorescence of groundwater inform about the role of the epikarst-unsaturated-saturated zones in the functioning of the system.