engleski

Recent hydrogeologic study of the Vis island

The Vis Island belongs to the group of the Middle Dalmatian islands. It comprises an area of about 90, 2 km2. Morphologically, three belts of highlands and two depressions with karst poljes are significantly marked. The highest point on the island is Hum with 587 m a.s.l. Island’ s water supply is organized from the water-supply station “ Korita” , situated in the central part of island, in the tectonically formed depression. On the Vis Island there are two additional captured objects: well K-1 above the Komiža town and the spring “ Pizdica” . The most important hydrogeological role on the island have two hydrogeological barriers, one in the Komiža Bay, completely made of impermeable magmatic and clastic rocks, and another one, recently recognized relative barrier in the area of Dračevo, Plisko and Velo poljes. Due to the fact that the island karst aquifer is in permanent dynamic relation with seawater, classical geologic, structural and hydrogeologic investigations have been extended with application of hydrogeochemical methods taking into account the natural chemical tracer content of groundwater and its variations in different hydrologic and vegetation conditions. Precipitation regime in this area is very unfavorable with regard to the recharging of island’ s aquifer because dry periods are usually very long. During the summer tourist season, when the number of inhabitants and fresh water consumption considerably increase, amounts of island’ s groundwater suitable for water supply and irrigation rapidly decrease. Sometimes, insufficient quantity of fresh water on the Vis Island causes restrictions. Concerning the development of tourist potential and present agricultural activities, summer lack of water is a seriously restrictive factor. Some results of performed hydrogeological study, important as a basis for island’ s fresh water potential assessment, will be presented.

Vis Island; hydrogeology; structural geology; hydrogeochemistry; karst; seawater influence

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