Trebišnjica

The Trebišnjica (Требишњица) is a river in Bosnia and Herzegovina, and the right tributary of the Neretva. Before it was utilized for hydro exploitation via various hydrotechnical interventions and systems with different purposes, Trebišnjica used to be a sinking river, rising and sinking through its course before resurfacing at various places from the Neretva river below the Čapljina to the Adriatic coast, and along the coast from the Neretva Delta to Sutorina. With a total length of above the ground, and roughly another below the surface, the Trebšnjica river is one of the longest sinking rivers in the world with the total of above and under the ground. In hydrological terms, it represents a sub-basin within the Neretva river basin. In classical antiquity, the river was known as the Arion, The Trebišnjica river originate near town of Bileća. The source of the river is a system of strong karstic wellsprings distributed in two principal aquifer zones, geographically and hydrologically distinct albeit in relatively close proximity to each other. In both zones group of wellsprings raises from the underground, consisting of a number of large, abundant founts each. The first, at the head of the river and at the outskirts of Bileća town, is the Trebišnjica wellsprings group, consisting of three large wellsprings, with Dejanova Pećina as primer outflow, and two secondary ones, wellspring Oko and Nikšičko Vrelo. The second zone, Čepelica river spring-group ("Čeplica spring-group") at Ćeplica village, is located further down the stream from first group. The Čepelica spring-group consists of two main karst hydrological features, Wellspring Čepo (Vrelo "Čepo") with three main outlets, and group of smaller estavelles (sinkholes) and springs on the left-bank side of the Čeplica river streambed. Formation of the Bileća Lake has affected the region significantly, both underground as well as at the ground level, with the extent of ecological impact still, after several decades, not being fully assessed.