engleski

Water Exploration on the Lastovo Island (Croatia) by Electrical Tomography and Seismic Methods

Water exploration was carried out at the island of Lastovo, situated farthest from the Croatian Adriatic coast. The investigated area is situated in a tipical karst field, close to the Lastovo town. Previous explorations and wells made in the sixtees were aimed at very shallow aquifers, mainly fine-grained sands, but because of the strong pumping, water has become brackish and has to be desalted by adequate technology. With respect to the fact that more water can only be captured from deeper aquifers, target rocks were fractured carbonate rocks in the bedrock of clastics. On the basis of all the data, electrical tomography data and seismic data, three positions for the exploratory boreholes were determined. The third borehole was not carried out, due to the results from the first two boreholes which were better than expected. The first borehole gave higher water quantities but with very high salinity, while the second one gave satisfactory quantities with very low salinity. Borehole results completely confirmed the results of the geophysical interpretation, and the conclusion can be drawn that the electrical tomography is very efficient in water explorations in coastal and island conditions, as well as in mapping of water quality (salinity). The seismic methods also need to be applied, at least at a promising part of exploration area, because they can help precisely define the vertical and lateral lithological changes, as well as determine faults and fractured zones, due to their higher resolution in comparison with the electrical methods.

water exploration; karst area; electrical tomography

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