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Example of problem solving of the salinity increase of the karst aquifers in Croatia

Karst costal aquifers have a great importance for the water supply of the costal area in Croatia, where the need for the fresh water is considerably increased because of the tourism development. Numerous captured costal springs are opened towards the sea influence which causes considerable problems in water exploitation during the summer dry periods. During the time, these problems could be increased in regard to the constant increase of the water consumption and the global climatic changes. Which are the possible solutions for the future? First, improvement of the exploitation conditions on the existing springs of the fresh water, because the existing infrastructure is connected to the sites of today’ s springs, and second, the accumulation of the high water waves or the usage of the existing water accumulation with the fresh water pipelines from sometimes distant locations. This article shows the example of the remedy of one important water supply spring in the area of north Adriatic Novljanska Žrnovnica, captured for the water supply of the important tourist area in the costal area of Croatia. The spring is situated in the deep small bay towards which a part of the karst catchment area of more than thousand km2 has been drained. Unfortunately, this great karst catchment area is open to the influence of the sea, which makes great problems in ensuring the normal water supply during the extremer summer dry periods. The attempts of designing and building the grouted curtain with the depth of 40 m, at the end of the seventies of the last century, have not given the expected results because of the depth of weathering and the natural connections of the sea and the fresh water system at the depths greater than the deepest part of the grouted curtain. This approach was abandoned in the middle of the seventies and the advantage was given to the exploitation management and to the investigation of the springs zone hinterland, outside the influence of the sea. The detailed hydrogeological investigations which included the analyses of the aero photos, making of the detailed hydrogeological map, geophysical investigation, investigation drilling, groundwater flows tracing and measuring the physical-chemical parameters in the boreholes up to the depths of 100 m under the sea water level , showed the possibility of the groundwater catchments in the zones outside the possible influence of the sea, in the conditions when the salinity in natural springs increases. In this way investigated costal springs zone with the observation wells with the depths up to 100 meters under the sea level can be important observation point for the evaluation of the negative influences of the expected global climatic changes on the eastern coast of the Adriatic sea, which can be incorporated in the organization of the observation net for the whole are of the Mediterranean.

Relation of the salt and the fresh water, Water catchment, Hydrogeological investigations, Hydrogeological investigations, Coastal karts spring, Novljanska Žrnovnica, Croatia

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