Studio idrogeologico del settore nord orientale dell’Altopiano carsico dei Sette Comuni (Asiago) con traccianti naturali ed artificiali

The Seven Comuni Plateau (Asiago) feeds a large karst aquifer whose main springs are located in the Brenta Valley and they are called Ponte Subiolo, Fontana Moretti, Cogol dei Siori e Cogol dei Veci. These springs provide on average 7,7 m3/s of water. If is considered a recharge of the acquifer of 20 m3/s, it is noticed that only 40% of the water flows out to these springs. In this research it is characterized a part of the water that infiltrates the karst massif and does not flow to the main springs. Here the North-Eastern area of the Plateau is studied. In this area of 200 km2 there are 60 km of karstic conduits where the water is transported from the summit to the springs located at the base of the steep northern slope of the Plateau. The caves on the top of the Plateau are predominantly vertical and descend for hundreds of meters inside the massif. The caves on the northern slope are predominantly sub-horizontal and they are called Bigonda and Calgeron Caves. The monitoring points, located both in the caves and on the valley floor were periodically sampled for chemical analysis, and it was measured the temperature, the electrical conductivity, the pH, and the discharge. The main springs of the study area have been monitored with dataloggers for measurement of electrical conductivity, temperature and level of the water. It revealed that T and EC are constant, this suggest the springs have diffuse dominated flow. The springs in Valsugana slowly pull out the neoinfiltration water through a large saturated zone, in case of heavy raining the springs do not efficently flow out the water supply and the phreatic level of the karstic massif rises and leads to the discharge of water from the entrance of the Bigonda cave and in extreme cases from the entrance of the Calgeron cave. A multiple dye-tracer tests was done from the summit of the Plateau, which has shown the exclusive connection to the spring in Valsugana and no connection to the springs of the Brenta Valley.