The Gacka Valley is a large karst valley fringed with mountain ranges of Velebit on the coast side and with Kapela Mountain on the inland side. The valley is dominated by the river Gacka which springs at one end of the valley and sinks underground on the opposite end. Gacka is the third longest sinking river in the world. Originally 32 km long, the river’s course was cut down to 11 km with the construction of the Hydro Electric Power Plant Senj in 1960. In the Otočac area, most of the river’s waters are diverted through tunnels to an artificial lake called the Gusić Jezero. Owing to a gently sloping terrain, the river’s course is tranquil and winding. The waters of Gacka are extremely clean and rich in oxygen.
The largest town in the Gacka area is Otočac, originally built at a river fork where the Gacka branches formed an “island” surrounded by water on all sides. Today Otočac has 4,000 inhabitants.
The Gacka source area consists of numerous smaller springs, the three strongest among them: the Tonković Vrilo, Klanac and Majerovo Vrilo. The springs resembling little lakes are very picturesque. To be seen here are many old watermills – malenice, many of which reconstructed and restored in a traditional style. There are also saw mills, fulling mills and cloth washing troughs. The people inhabiting the Gacka area navigated the river using plav, traditional boats carved from fir tree trunks, typical for the Gacka. The river is rich in diverse water plants which are so abundant that people harvest them as cattle feed. Until 1937, only four fish species inhabited the Gacka: trout, European eel, weather loach, and pike, probably introduced during the reign of the Frankopan dukes. Gacka also provided habitat to stone crayfish which disappeared in 1931 due to crab plague. Later, numerous other fish species were introduced into the Gacka, while other made their way to the river through the canal built between Gacka and the Lika rivers to serve the Hydro Electric Power Plant. To be found in the Gacka today are also the rainbow trout, grayling, carp, tench, roach, chub, and pumpkinseed. These introduced species have disturbed the biological balance and reduced the purity of water. Trout in the Gacka grow very fast (about five times faster than in other karst rivers) and are known among anglers throughout the globe.
The Gacka once sank in three sinking areas: Ponori near Švica, the Gusić Polje and the Hrvatsko Polje. In the Otočac area, the river course used to fork into two branches, the southern branch forming two lakes at Švica, connected by a 50 m waterfall. This area used to be called the "“Little Plitvice Lakes”", and also abounded in watermills, water-operated saw mills used for sawing timber transported down the river, fulling mills and troughs, even a small hydro electric power plant built in 1936 that supplied the town of Otočac and the surroundings villages.
The sinking area of the Gacka River is today threatened by reduced water volume and collapsing travertine barriers along the river due to insufficient amount of water. Because of this, the Croatian Speleological Server has included it among the 10 most endangered karst areas in Croatia. Like other karst fields, this area abounds in many rare and protected plant species, among them early marsh orchid, small-fruited yellow sedge, and greater spearwort, that are included in the red list of threatened plants in Croatia. These fields are also valuable habitats for many birds, which is why the Gacka Valley, together with other karst fields, has been proposed for protection through the European Ecological Network NATURA 2000 as an important bird habitat. In addition, the Gacka Valley and the surrounding area contains twelve more areas important for species and habitats that have been proposed for the Natura network, among them the Gacka Valley, the Gacka River, bog in Čovići, the Majerovo Vrilo spring, the Pećina cave and several other caves.
The Gacka River springs have been proclaimed a natural monument, and the Gacka and Dabar valleys have been placed on the significant landscape list.
Set up in Otočac in 2006, the Croatian Center for Indigenous Species of Fish and Crayfish in Karstic Waters is engaged in farming trout and crayfish to be introduced into the Gacka and for commercial use. It also engages in scientific research of the Gacka area and its inhabitants, especially the trout, and develops local brands and tourist offers.
The oldest evidence of human habitation in the Gacka valley, discovered in the Pećina cave, dates back to the Middle Stone Age. Early Illyrian finds were discovered in the Bezdanjača cave near Vrhovine containing one of the largest cave necropolises in Europe. Unearthed in the Gacka valley are also Late Bronze Age remains of several Illyrian settlements of the Iapodes tribe. Testifying to the later Roman occupation are the remains of the central settlement Arupium and several Mithraic temples dedicated to the sun god Mithras, adopted by the Romans from the Persians, whose cult was spread by the Roman soldiers. In the Middle Ages, the Gacka played an important role in the first Croatian state and the town of Otočac is mentioned on the Baška Tablet. The Frankopan dukes built a number of fortifications, the central ones being those in Otočac and Brinje. During the Turkish invasion, the Gacka was at the very border of occupied territory and had fortifications and defense towers, such as Kalin Grad. Many villages were abandoned during the Turkish rule but were resettled again after the Turks left the area. In the recent Homeland War, the Gacka area suffered great destruction and human loss, with mine fields left as reminders of the war.
The traditional life of the people inhabiting the Gacka valley was closely tied to the river. These modest, hard-working people lived in small stone houses with wooden shingle roofs and wore simple traditional dark-colored clothing with unobtrusive patterns. Wool cloth made from the wool of the indigenous Lika sheep breed Pramenka. was the principal clothing material. Traditional men’s apparel included the typical red cap which is said to have been fashioned after the Iapodian women’s metal headgear. Wool was also used for making traditional shaggy blankets called biljac.The traditional diet of the Gacka people was simple and wholesome: smoked pork with sauerkraut, baked potato halves and bacon, sausages, roast meat, stuffed cabbage leaves, polenta and sour milk, home-made cheese, lamb on the spit, smoked ham, Gacka trout, and šljivovica, a spirit distilled from plums.
How can you spend your time in the Gacka Valley?
Vrila Gacke Springs: walk around the lakes at the river source; visit the Info Centre at Majerovo Vrilo – see a flour milling demonstration and buy freshly ground flour or eat Gacka trout fresh from the river.
The Gacka River: You can walk or cycle (but stick to the marked path or road because of the danger of mines!), take photos of the landscape and water birds, angle (angling permits can be obtained at Ličko Lešće, Sinac, Čovići, Prozor, Otočac and Švica).
Otočac: visit the Gacka Museum and enjoy archaeological Iapodic, historical and ethnographic collections or the 17th century. Holy Trinity Church, and explore the remains of the old fortress on the Fortica Hill where an archaeological dig is currently under way.
Ličko Lešće: Visit the Center for Indigenous Species of Fish and Crayfish in Karstic Waters that provides information and guidance; you can walk along the marked path from the Center to the Pećina archaeological site, the source of the Gacka tributary Kotelka, and to the lookout point.
Warning: Parts of this region are still covered in mines!
There are minefields in the Gacka river area in the direction Sinac – Otočac, in parts of the north eastern suburbs of the town of Otočac and in the wider area of Drenov Klanac (former right arm of the Gacka river). Unfortunately, not all mined areas are marked and you are therefore warned not to walk outside roads or frequently used pathways or outside the mentioned areas. For a map of mined areas, visit the website of the Croatian Mine Action Center!
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