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Karstic aquifers are well known for their vulnerability to groundwater contamination and many different types of anthropogenic impact. The karst of Dinarides is manly open karst environment with characteristics such as a thin soil cover, mostly permeable overlaying deluvial sediments of karst poljes with swallow holes, shafts and sinkholes. In comparison with other types of aquifers, rapid infiltration rates which include point or diffuse recharge and underground flow thought a high permeability conduits and different size of fracture and cavernous systems. A concept of groundwater vulnerability assessment quantifies the sensitivity of an aquifer to human activities impact on groundwater contamination (CIVITA, 1994 ; DORFLINGER, ET AL., 1999 ; COST, 620). One of the first approaches focused on aquifer vulnerability mapping was SINTACS scheme, established for hydrogeologic, climatic and impact settings typical for the Mediterranean countries (CIVITA & DE MAIO, 2000). The procedure of the method incorporates seven parameters relevant for the contaminant attenuation capacity and vertical flow features: depth to groundwater, effective infiltration action, unsaturated zone attenuation capacity, soil/overburden attenuation capacity, hydrogeologic characteristic of the aquifer, hydraulic conductivity range of the aquifer and hydrologic role of the topographic slope. Jadro and Žrnovnica springs are a major source of fresh potable water area for over 300.000 inhabitants of the Split town and surrounding settlements. A recharge of springs is approximately 500 km2 and mainly is composed of carbonate rocks, well permeable Mesozoic, Eocene and Perms limestones, dolomites and impermeable lower Triassic clastic deposits and Eocene flysch. Increasing anthropogenic pressures in inland part of recharge area and increasing trends of some contaminant content in spring waters initiated a comprehensive study which included detailed geological, morphological, structural, hydrogeological, geochemical and environmental isotope research. On the basis of obtained data selected parameters were presented in appropriate grid information layer scale 1:25 000 and processed by GIS following the SINTACS R5 standard scheme (CIVITA & DE MAIO, 2000). Also, standard scheme was modified within the hydraulic conductivity parameter layer by incorporation of the density of dolinas. Applied modification decrease the area of extreme and very extreme vulnerability assessment of the karst aquifer and increase very small, small, medium and high vulnerability parts of the recharge area. Besides the fact that modified approach enhanced land-use potential, further tests and modeling procedures should analyses its implications on the protection of these very valuable groundwater resources. |
