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Coastal and submarine springs of Rovanjska – Modrič area (Croatia)

Croatian Adriatic coastal belt is mostly built of intense karstified carbonate beds with well developed karst drainage systems and various types of karst aquifers well connected with hinterland. Along the coast there are zones with intense groundwater-seawater interactions marked by: a) groundwater discharge into the sea in the form of submarine and coastal springs, b) seawater penetration into karst aquifers, c) development of unique geomorphosites and habitats of high vulnerability to natural hazards and climate change. Their development and characteristics were mainly controlled by lithological composition, tectonic events, hydrogeological conditions, Late Pleistocene/Holocene sea level change and climate. Recently there is also quite aggressive anthropogenic impact in some restricted areas. In the conditions of recent climate variations and increased demands for fresh water, especially during the tourist season, the multidisciplinary researches of karst aquifers needs more attention by scientific, environmental, economic and government sector. The area of Rovanjska - Modrič in northern Dalmatia is well known for very well developed coastal karst aquifer with submarine springs (local terms: vrulja, jezero) and numerous coastal springs. It was developed in karstified Crecateous and Paleogene-Neogene carbonate beds (mainly limestone and breccia). The development of the aquifer was determined by conditions of a mixed autogenic-allogenic system. The main inputs of fresh water are from: a) the hinterland (Lika region) in the form of sinking streams flowing underground towards the coast and b) the high precipitation in Velebit Mt. area. The largest submarine springs are Vrulja Modrič and Vrulja Zečica. Using speleodiving techniques in Vrulja Zečica 197 m of submerged passages were mapped (of about 650 m of known passages till the depth of 43 m). In Vrulja Modrič there was about 500 m of passage explored (up to 27 m deep). Both are characterized by seasonal water outflow and by well developed, spacious passages. During inactivity period seawater intrusion and anchialine conditions were recorded. In the area there are also three zones with high concentration of coastal springs. Research project in 2012 was aimed to their mapping and water sampling using field measurements and lab analysis. Concentrations of 16 elements, nutrients, physical and chemical indicators were determined. According to the first results there is no pollution of anthropogenic origin recorded.

coastal aquifer ; submarine spring ; coastal spring ; trace elements

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