FRACTIONATED DRAINAGE IN A KARSTIC ALPINE BASIN OF THE ITALIAN DOLOMITES

High-altitude alpine karstic systems often develop in highly fractured carbonate rock. The complexity of the fracture network leads to an equally complicated surface and subsurface drainage system. Rainfall, snow melt, and glacial melt water move quickly through karstic rock, often discharging at streams many kilometers away and providing an important source of drinking and irrigation water for local communities. For example, in the Trentino Region of the Brenta Dolomites (NE Italy) karstic springs supply about 50% of the water to local aqueducts. In this study, we compare surface drainage patterns derived from high-resolution LIDAR topography to subsurface (cave) discharge measurements. Both analyses demonstrate that rainfall and snowmelt drain over distances of only 10's of meters before diving into sinkholes and entering the karst drainage network. The time lag between initiation of snowmelt and response at caves in the subsurface is less than an hour. The absence of surface and subsurface storage suggests a water supply system that is highly dependent upon yearly snow accumulation and, therefore,is extremely sensitive to climate fluctuations.