engleski

Possibilities of increasing fresh water abstraction on the karst island of Korčula (Croatia)

Adriatic karst island of Korčula has one active pumping site with dug wells in the central-west part of the island (Blatsko polje), which supplies water to the central and western part of the island, while the eastern part of the island is connected to submarine water pipeline, and receives water supply from the mainland. Seaside tourism is the main branch of the island’s economy, and the highest quantities of water are therefore required during the summer season, when the groundwater levels reach their minimum values. Seawater penetrates in wedge-like form from coastal zones, and reaches the Blatsko polje karst aquifer only in extreme hydrological conditions, when two or more dry years repeat in a role. This penetration happens mostly through fault and fractured zones which are highly karstified. In such cases, oversalinization of water was already recorded. Climate modelling predicted a gradual decrease in annual precipitation and increased irregularity of the rainfall with more frequent storm events, characterized by low infiltration and pronounced surface run-off. Therefore, it would be more favourable to disperse pumping wells on a larger area, if hydrogeological conditions allow it. Western from the Blatsko polje, Vela Luka Municipality has shown some initial perspective, taking into consideration the geological structure and arrangement of permeable vs. impermeable rocks. Initial study was performed, which included the hydrogeological field inspection in search for submarine fresh water springs (vrulja), as well as a geophysical survey by four profiles (total length 2818 m) of electric tomography (ET), which has proven to be very useful in karst island aquifers research. As a result, three prospective areas for fresh water intake were delineated and ranked according to their potentiality. Research should continue in one of the following directions: (i) detailed hydrogeological mapping and seismic refraction profiling in the areas deemed promising in the ET cross-sections and/or (ii) proceed directly to drilling of wells at a few favourable locations with constant hydrogeological supervision and state-of-the-art pumping tests including step-test with three steps and constant-test in the conditions of hydrological minimum, constant electroconductivity (EC) logging and water sampling and hydrochemical analyses.

water supply, electric tomography, Adriatic karst island, salt/freshwater relations

nije evidentirano