Hydrochemical and isotopic characterization of carbonate aquifers under natural flow conditions, Sierra Grazalema Natural Park, southern Spain
Damián Sánchez, Juan Antonio Barberá, Matías Mudarra, Bartolomé Andreo, José Francisco Martín, 2018. "Hydrochemical and isotopic characterization of carbonate aquifers under natural flow conditions, Sierra Grazalema Natural Park, southern Spain", Advances in Karst Research: Theory, Fieldwork and Applications, M. Parise, F. Gabrovsek, G. Kaufmann, N. Ravbar
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We used hydrogeochemical techniques and environmental isotopes (δ18O and δ2H) to characterize karst aquifers without a well-known hydrogeological conceptual model. The selected study area corresponds to carbonate outcrops located in the Sierra Grazalema Natural Park (SGNP) in southern Spain. The combination of high rainfall, large areas of carbonate outcrops and the high permeability of the outcropping rocks means that the SGNP is a strategic water reserve in a region that periodically suffers from a scarcity of water. There are still many uncertainties regarding the hydrogeological functioning of these aquifers, such as the groundwater flow paths, the identification of recharge areas and a possible hydrogeological connection with adjacent systems. The objectives of this work were: (1) to gain an insight into the hydrogeochemistry of groundwater in the SGNP aquifers; (2) to identify the recharge areas of the main springs of the karst system; and (3) to contribute to our understanding and conceptualization of the SGNP aquifers. Our results show marked differences in the chemical composition of the groundwater, which can be classified into three main groups: CaHCO3 waters (southern sector); Ca–MgHCO3 waters (northern sector); and those with higher SO4 2−, Na+ and/or Cl− concentrations. These hydrochemical differences are principally dependent on the mineral composition of the rocks the groundwater flows through and comes into contact with. These results also shed light on the recharge areas associated with the main springs and seem to corroborate a possible net groundwater flow from the eastern part of the SGNP (Sierra del Endrinal) towards carbonate outcrops situated several kilometres to the SE.
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Karst landscapes and karst aquifers are composed of a variety of soluble rocks, such as salt, gypsum, anhydrite, limestone, dolomite and quartzite. They are fascinating areas of exploration, study and research. As karst rocks are abundant on the Earth’s surface, the fast evolution of karst landscapes and the rapid flow of water through karst aquifers present many challenges from a number of different perspectives. This collection of 25 papers deals with different aspects of these challenges, including karst geology, geomorphology and speleogenesis, karst hydrogeology, karst modelling, and karst hazards and management. Together these papers provide a state-of-the-art review of the current challenges and solutions we face in describing karst from a scientific perspective, while at the same time providing useful data and information for managing karst territories to land planners, developers, and managers of show caves, natural parks and reserves in karst terrains.