Le acque del Carso Classico

Classical Karst is approximately 900 km2 and extends from SE of the Isonzo River to Postumia town and it is characterized by the large variety of karst features. For this reason, this area is the best example of karst worldwide. Classical Karst hydrogeological model has been subdivided in three different sectors: one in which the surface waters become underground and therefore feed the deeper karst aquifer, one in which these waters moves in the deeper part of the aquifer and are nourished by local precipitation and one in which these waters finished in the Adriatic Sea or in local springs that feed several small lakes and the large spring of Timavo River. Classical Karst is marked by deep and well developed karstic features. In fact, in the Italian part of the Classical Karst more then 3000 caves have been found. Of these, 150 are more then 100 m developed and ten of them are extended more then 1000 m. In addition, in this area of the Karst, 80 dolines with a diameter of more then 100 m are present and limestone karren pavements extend for several km2. Six kilometers after the Skocjan sinkhole, the Timavo underground waters run into the deeper galleries of the Abisso dei Serpenti (Kačna Jama) located at 140 m a.s.l. Approximately 15 km southward, the Timavo waters runs at 10-20 m a.m.s.l. in the deepest part of four vertical cavities that are 300 to 370 deep and are located approximately 20 km northward of the resurgence area. One of these, the abyss of Trebiciano, has been known for long time, whereas the others named Grotta of Kanjeduce, the abyss of the Strsinkna doline and the Grotta Meravigliosa di Lazzaro Jerko have been discovered recently. The spring system is formed by the Timavo Spring located in San Giovanni of Duino, the Doberdò and Pietrarossa Lakes and by small springs that feed the Lisert and Moschenizze channels (for a total area of 30 km2) and by the coastal-marine springs along the Trieste’s Gulf and Duino Aurisina villages (approximately 8 km). The waters in these spring system are from different aquifers that are interconnected between them and have an average discharge capacity of 40 m3s-1 and a maximum of 175 m3s-1. Hydrochemically these waters have similar ion concentrations. However, changes have been found in the water hardness and in chlorine quantities. This data together with the oxygen stable isotope results allow to dive them into: - Timavo Spring, with Alto Timavo waters (Reka River); - Sardos e Moschenizze Sud Springs, feed by the Isonzo River waters and with waters from the Alto Timavo only during floods; - Sablici, Moschenizze Nord, Lisert Springs and Doberdò Lake, characterized by a dual water source: from the Timavo River and from Isonzo River with a marked increment of these waters towards Moschenizza Nord and Doberdò Lake; - Aurisina Spring, nourished by karstic waters and with a small contribution from the Alto Timavo.