Gacka is a

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of ...

located in the

Lika Lika () is a traditional region of Croatia proper, roughly bound by the Velebit mountain from the southwest and the Plješevica mountain from the northeast. On the north-west end Lika is bounded by Ogulin-Plaški basin, and on the south-east b ...

region in central

Croatia , image_flag = Flag of Croatia.svg , image_coat = Coat of arms of Croatia.svg , anthem = " Lijepa naša domovino"("Our Beautiful Homeland") , image_map = , map_caption = , capi ...

. Because for a large part of its course it is a subterranean river, estimates on its length vary. The overground part has undergone substantial human intervention - before it was long; now it is only long.

Lika-Senj County Lika-Senj County (, hr, Ličko-senjska županija) is a county in Croatia that includes most of the Lika region and some northern coastline of the Adriatic near the town of Senj, including the northern part of the Pag island. Its center is ...

Tourist Board, It has been regulated by man to flow into an aqueduct in Gusić polje (known as Tunel Gacka-Gusić Jezero) and then into the

Adriatic Sea The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkan Peninsula. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Sea) to th ...

through a hydroelectric installation ''HE Senj'' near

Sveti Juraj Sveti Juraj is a village in Croatia. It is on the Adriatic coast, on the D8 highway between Senj and Karlobag. A minor road leads inland to the Northern Velebit National Park The Northern Velebit National Park ( hr, Nacionalni park Sjeverni V ...

. HE Senj takes inflow from Gacka and

, since it was built in 1965. The river passes through

karst Karst is a topography formed from the dissolution of soluble rocks such as limestone, Dolomite (rock), dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathe ...

fields and most notably the town Otočac, and its headwaters are known as a popular locale for

trout Trout are species of freshwater fish belonging to the genera '' Oncorhynchus'', '' Salmo'' and '' Salvelinus'', all of the subfamily Salmoninae of the family Salmonidae. The word ''trout'' is also used as part of the name of some non-salm ...

fishing.‘Trout Fishing in Yugoslavia Plumbs the Depths of Emotion’
nytimes.com MARCH 5, 1972

References

Rivers of Croatia {{Croatia-river-stub