Karst spring of Fontanon di Goriuda: geochemical investigations to attempt the answers at the hydrogeological and groundwater flow paths questions of Mt. Canin. (Italian –Slovenian Western Julian Alps

Recent results obtained from the underwater cave explorations from the cave of Fontanon di Goriuda, have inspired new geochemical investigations of the water.These data attempt to improve the hydrogeological knowledge and the groundwater paths considerations. The Canin massif contributes waters to three river basins, theAdriatic Sea, and the Black Sea. It is located at the border between Slovenia and Italy which follows the top line of the ridge and it basically comprises an Upper Triassic series of Norian dolomite (the Main Dolomite) overlain by up to several hundredmetres of Dachstein Limestone. It is bordered by the Možnica and Koritnica valleys in the northeast and east and by the Soča Valley in the south. On the west it is borderedby the Uccea Valley, the Idrija fault zone, and the valley of the Resia River that flows into the Tagliamento River. The Raccolana and Rio del Lago valleys that form thenorthern boundary of the Canin massif run along the Raccolana fault zone. The geological structure causes springs to occur on its flanks, mainly in the Bovec Basin(Bočič, Boka, Sušec-Mala Boka, Žvika, Vodica, Glijun, Kladenki, Srnica) to the southand Možnica, Goriuda to the north. Due to their copiousness and constancy, the waters of the Kanin massif have been always important for the residents of the BovecBasin for survival (drinking water), practical (protection from pollution and Since the quantity of water is limited and a great part of it is not accessible, great caution isnecessary in planning the exploitation of water resources. For this reason,researchers have intensively studied the catchment areas of Kanin’s karst springs for decades to determine the minimum discharges that will provide a sufficient watersupply and the extent and permeability of the karst bedrock floods), economic (hydroelectric power), and symbolic reasons. In 1999 (Casagrande, Cucchi, Manca1999) was carried out a monitoring campaign of the karst springs in the southern andnorthern Canin massif. The aim of the experiment was monitoring in detail thebehavoir of the springs during a strong rainy event. Were considered the following parameters: the discharge, the physical and chemical characteristic and the δ18O and δD ratio. The springs were: Fontanone M. Sart (Resia), Fontanon of Goriuda, SellaNevea and Rio del Lago springs, Boka, Glijun and Zvicar. Simultaneously were analyzed the precipitation collected from pluviometers installed in Val Resia (400ma.s.l.), Rifugio Gilberti (1850 a.s.l) Val Raccolana-Fontanon di Goriuda (750m a.s.l). Thanks to this first approach it was possible to classify Fontanon of Goriuda as adreno dominante spring conditioned by rapid flow through larger channels in the ystem. The Karst springs collect water from different levels and have differing discharge regimes, a multi-level aquifer has developed along the main fissured zones.In 2009, 2010 and 2011, cave divers have sampled the waters of the three siphons inside the cave at different water depth and in different months as also the percolationalong the main gallery after the siphons. These waters were analyzed for the for δ18Oand δD isotope determination. The δ18O and δD ratio of the stream at the entrance, of the three siphons at the surface and a 6m deep so as the percolation, are depleted with the seasonal precipitation of the area . Instead the water of the II siphon at about 14m deep shows the absolute values of the isotopic data typical of the high altitude areainfiltration. This result is in according with the isotope values and with the conductivity variation found at the Sella Nevea springs (Casagrande, Cucchi, Manca1999). The Goriuda cave has to be yet explored, during the last expedition, theresearches have founded new conduits and galleries they should be the unknown subterranean path flow of the aquifer of the Kanin massif connecting the Italian andSlovenian part. More detailed water tracing investigations should therefore be undertaken to provide a significant amount of data for ensuring the protection of thearea. The decision-making authorities should further consider the importance of highmountainkarst areas, their role in everyday life, and the use of their resources today and tomorrow. In all probability, the importance of the Kanin massif will increase dueto its international position and the proximity of densely populated areas that lack good (potable) water resources.

کلیدواژه ها:

karst aquifer ، hydrogeology ، isotopic analysis ، human water supply