engleski

Hydrogeological investigations in the watershed of spring Kakma, southern Croatia

Kakma is a pressure spring which is tapped and included in the local water supply system of the towns Biograd na moru and Benkovac. This spring is situated in Croatian coastal karst belt which is called «Ravni kotari». Inflow area of this typical karsts spring is composed of the carbonate rocks and minor part of flysch deposits. Occurrence of the spring is related to the fault contact Eocene limestones and Eocene Age flysch deposits. The aim of this survey is to define zones of sanitary protection and confirm eastern boundary watershed of the spring Kakma. Ground water flow is established by hydrogeological investigations respectively with dye-tracing techniques. Dye-tracing was done with 10 kg Na-fluorescein which was poured into an abyss Zapužane. Observed springs are situated on the edge of Vransko polje at the distance of 5, 0-7, 5 km from the abyss. The velocities of the monitored springs are established as follows: Mali Stabanj 6, 7 mm/s, Veliki Stabanj 6, 5 mm/s, Pećina 5, 5 mm/s and Biba 6, 7 mm/s. There is no confirmed connection between the abyss Zapužane and spring Kakma by ground water analysis. Up to now the investigations showed that the eastern part of watershed does not belong to spring Kakma but springs Mali Stabanj, Veliki Stabanj, Pećina and Biba are part of the watershed. Due to obtained results the ground water dye-tracing test suggests that the zones of sanitary protection need to be defined after the new hydrogeological investigations which will determine the boundary between the two watersheds respectively between watershed of spring Kakma and watershed of springs Mali Stabanj, Veliki Stabanj, Pećina and Biba.

karst; groundwater protection; dye-tracing techniques; spring Kakma; Ravni kotari; southern Croatia

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