Hydrological characteristics of the Reka river catchment on a flysch - karst contact

The Reka river is the widest known sinking stream of the Classical Karst area in Slovenia, and it has been studied since the Antiquity. The river sinks into the Skocjan Cave system, which was proclaimed by UNESCO as a World Heritage Site in 1986. The Reka river basin is situated in the southern part of Slovenia and has an area of 442 km2 and a mean discharge of 8.2 m3/s. The basin has a unique geological structure; it is situated on the Brkini syncline Eocene flysch rocks surrounded by a large karstic region. The stream network density is about 1.696 km/km2. The water from the northern karstic formation belongs to the Danube River Basin, while the water from the southern part drains into the Adriatic Sea. There is an underground bifurcation from which the surface water flows to the Danube River and the underground water drains in the Bistrica Spring, a tributary of the Reka River.