engleski

Water exploration on small Croatian islands by electrical tomography and refraction seismics

Water exploration was carried out at the three Croatian islands: Susak, Dugi otok and Molat. As it can hardly be expected to discover fresh water on a small karstic island, the main goal was to get the water of as low a salinity as possible, since the price of desalinization technology depends on the water salinity. In the first phase hydrogeological mapping of the entire islands was carried out and main goal was to determine microlocations for detailed investigations. Extracted microlocations were covered with a relatively dense network of geophysical profiles and the results of the geophysical interpretation enabled us to locate the optimal positions for exploratory boreholes. All three islands are placed in the region of Dinarides, which means that the exploration was carried out in the karst areas, which are very difficult environment for geophysical and any other exploration, mainly because of high surface inhomogeneities and uneven lithological boudaries. The main goal of geophysical explorations was to uncover fault and fractured zones, that are usually main aquifers in karst areas. Therefore, three geophysical methods were applied: electrical sounding, surface electrical tomography and refraction seismics. During the first phase electrical sounding method was applied to gain the general insight into the area explored and optimal positioning of tomographic profiles. The basic data regarding lithological and tectonic relationship was acquired through 2-D electrical tomography. The discovered zones of lower resistivities and the rock fracture degree, as well as the compact rock basement were precisely mapped using the refraction seismics. Out of three specified and thoroughly explored microlocations, two provided us with positive results from the hydrogeological point of view. The third location showed no presence of water, but the results of geophysical exploration clearly pointed out that the positive results are very unlikely. The established exploration procedure was very successful and will be used during further exploration of other small Croatian islands.

water exploration ; electrical tomography ; seismic refraction ; karst

nije evidentirano