The Trebià ¡njica () 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, Trebià ¡njica used to be a sinking river, rising and sinking through its course before resurfacing at various places from the Neretva river below the ÃÂapljina 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 Trebà ¡njica 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 Trebià ¡njica river originate near town of BileÃÂa. 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 BileÃÂa town, is the Trebià ¡njica wellsprings group, consisting of three large wellsprings, with Dejanova PeÃÂina as primer outflow, and two secondary ones, wellspring Oko and Nikà ¡iÃÂko Vrelo.
The second zone, ÃÂepelica river spring-group ("ÃÂeplica spring-group") at ÃÂeplica village, is located further down the stream from first group. The ÃÂepelica spring-group consists of two main karst hydrological features, Wellspring ÃÂepo (Vrelo "ÃÂepo") with three main outlets, and group of smaller estavelles (sinkholes) and springs on the left-bank side of the ÃÂeplica river streambed.
Formation of the BileÃÂa 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. Entire system of the Trebià ¡njica wellsprings, its both groups, were part of the characteristic Dinaric karst landscape, with significant aesthetic value. However entire area surrounding the Trebià ¡njica river, its headwaters with sources, Miruà ¡ka valley, Popovo Polje, many villages and productive land is flooded in 1967 by the BileÃÂko Lake, formed after construction of the GrnÃÂarevo dam, with the primary purpose of serving as an artificial water reservoir for the Trebinje-1 Hydroelectric Power Station turbines.
As it flows in an area of karst (limestone), the Trebià ¡njica actually represents a very complex system of the above and underground streams. It originates in Bosnia and Herzegovina from two streams from the Lebrà ¡nik and ÃÂemerno mountains:
The river shortly re-appears in the FatniÃÂko Polje, where the village of Fatnica is largest settlement, under the name of FatniÃÂka rijeka (River of Fatnica), only to sink again after a short flow above the ground.
After a total underground flow of some , the waters of the sinking FatniÃÂka rijeka re-appear as a series of very powerful cave springs near the town of BileÃÂa, which are joined into one river, the Trebià ¡njica, the most important river in eastern Herzegovina. The river flows to the south, through the depression of Miruà ¡a. On the southernmost part of the depression, the river is dammed by the Grancarevo Dam at the village of Gornje GranÃÂarevo and completely flooded upstream by the artificial Lake BileÃÂa. Nearly all of the eastern bank of the lake belongs to Montenegro.
The Trebià ¡njica turns west between the villages of Donje GrnÃÂarevo and Lastva into the Trebinjsko polje (Field of Trebinje), being dammed again at Gorica, with a small reservoir. The river continues to the west following the southern slopes of Bjelasnica mountain, through the town of Trebinje and villages of Draà ¾in Do, Tvrdoà ¡, Gornja KoÃÂela and Donja KoÃÂela, and enters the largest karst field in the Balkans, Popovo Polje (Priest's Field).
In Popovo Polje, the Trebià ¡njica used to sink (see Regulation below), right after the Trebinje. In the field, the river turns northwest, next to the villages of Staro Slano, ÃÂediÃÂi, Dobromani, à ½akovo, Tulje, Sedlari, Grmljani and Zavala, near the Vjetrenica cave, the largest in Bosnia and Herzegovina. The river then turns north, curves between the villages of Dvrsnica, Oraà ¡je, ÃÂavaà ¡ and TurkoviÃÂi and in the lower Popovo Polje, near the Croatian border, sinks into the several big sinking holes (most notably, the Doljaà ¡nica and Ponikva holes.
The waters of the Trebià ¡njica from the Popovo Polje, re-appear as three separate outflows:
The total drainage area of the Trebià ¡njica covers , of which is shared with the Neretva drainage area (the spring of ÃÂapljina). The drainage area of the central, longest part of the river covers .
As a river that flows in geologically unstable terrain (karst) and with such an interrupted flow, the Trebià ¡njica contains enormous potential for hydroelectricity production. As a result, regulatory works on the Trebià ¡njica were arguably the most massive ones in the former Yugoslavia.