Una (Sava)

According to local legends, the river was named by the Romans who, after seeing it for the first time, said una (lat. one, as a reference to its unique beauty) to describe it. Una is a popular female name even in the areas that are not located in the vicinity of the river. One explanation for this is that people that were displaced during the Yugoslav Wars continued to give the name to their children. ==Geography==

Sources The source of the Una river is located near the Croatian village of Donja Suvaja and consists of multiple smaller springs. The largest spring by discharge is a large karst spring at an elevation of above sea level, called Vrelo Une, and is considered to be the main spring of the river. The water, originating from great depths, forms a round, calm, bluish green lake, thirty meters by fifteen meters in size, surrounded by forests and steep cliffs of the Lička Plješevica and Stražbenica mountain ranges. The Una river, flowing out of the spring, forms its first travertine cascade roughly 20 meters downstream and another large waterfall 3 – 4 meters in height roughly 100 meters downstream. The spring itself was explored and mapped up to a depth of 248 meters, which makes it the deepest explored spring in the Dinaric karst region and the fifth deepest in the world. Due to its unique aesthetic, ecological, geomorphological and hydrological value, the spring and the surrounding region, totaling an area of , were declared a natural monument in 1968. The karst aquifer of the Una is located mostly in the territory of Croatia. The aquifer itself takes up a large area from Korana in the northwest to Velika Popina in the southeast. It encompasses the mountainous areas of the Lička Plješevica, Čemernica and Mala Kapela mountains, and the Koreničko, Bijelopolje, Krbavsko and Lapačko polje karst fields. All aforementioned karst fields are directly connected to spring of the river itself, and other nearby springs (Klokot, Vedro Polje, Dobrenica, Ostrovica). The discharge of the spring varies from a minimal recorded in 1987 to a maximal recorded in 2009, with the average discharge being . The spring seems to have a limited outflow capacity, potentially caused by limited dimensions of the karst outflow channel, water retention in the karst, water flowing under pressure and water overflowing into other watersheds. The total amount of water that flows out of the spring yearly ranges between and . The temperature of the water varies in relatively narrow margins of with an average of , which also leads to the conclusion that the surfacing water spends a large amount of time in the karst underground. The average, minimal and maximal monthly and yearly discharges seemed to have increased in recent times, contrary to a trend of decreasing discharges from other springs in the nearby regions believed to be caused by global warming. Upper course The upper part of the river spans from its source to the city of Bihać. After emerging from its source, the river flows for about 5 km before reaching its confluence with the Krka river, after which it forms the border between Bosnia and Croatia for about 7 km and then enters Bosnia completely for the first time, flowing through the village of Martin Brod where it forms a cascade of waterfalls with the total drop being about . Downstream of Martin Bord, the Una more than doubles in size at its confluence with the Unac. After 9 km the river bends west at the town of Kulen Vakuf where it is joined by the small tributary Ostrovica before continuing to flow in a general northward direction. Downstream of Kulen Vakuf, the river meanders through a valley by the village of Klisa before again meeting the Croatian border after about 8 km. This time, the river forms the border for about 18 km and cuts through a gorge, forming a cascade of rapids and waterfalls, the biggest and most notable being the Štrbački buk. After entering Bosnia completely for the second time, the rivers forms the Troslap and Dvoslap waterfalls, after which it exits the national park and flows through the villages of Lohovo and Račić. After that, the river slowly enters the Bihać field, flowing through the villages of Ripač, Golubić and Pritoka, taking in the waters of the Dobrenica and forming multiple river islands and small waterfalls, before finally entering the city of Bihać after about 70 km of total flow. In Bihać, the river forms multiple islands of varying sizes, often surrounded by small waterfalls, some of which are private property while others are public and often popular bathing sites. The core of the city itself is surrounded by the Una river, and a channel carries water from the river to a small hydroelectric power plant. Another small tributary of the Una, the Drobinica, flows through the city in a regulated channel before merging with the Una. In its upper course, the Una is a youthful river with a steep gradient of 0.232% and a large amount of waterfalls. The total drop is over a distance of . The deposition of carbonate minerals and the formation of porous limestone rock (tufa) and pronounced karst influence is characteristic for this section. Middle course The middle section of the river spans from the city of Bihać to the town of Novi Grad and its confluence with the Sana. Not long after exiting the city the river takes in the waters from the short Klokot river, after which it meanders, slowly turning eastward before entering the village of Pokoj where it takes a sharp turn north and enters a canyon between Bihać and Bosanska Krupa where it slowly turns eastward again. The Una Kostela hydroelectric power plant is located not long after the entrance into the canyon and is currently one of two hydroelectric power stations on the main course of the river, the other being the small Bihać power plant. The canyon is, on average, around deep with lush vegetation growing on its cliffs. A road that connects Bihać and Bosanska Krupa follows the river through the canyon. After flowing for about 27 km through it, the river exits the canyon and enters the town of Bosanska Krupa where it takes a turn north. Like in Bihać, the river forms multiple islands surrounded by small waterfalls. Downstream of Bosanska Krupa, the river takes in the waters of the short Krušnica river before heading north towards the town of Bosanska Otoka, after which it forms the Inter-Entity Boundary Line and shortly after forms the border with Croatia for the last time, and remains a border river until its mouth. Not long after becoming the border, the river enters the town of Novi Grad, where the confluence with the Sana river is located. The Sana is the longest and most significant tributary of the Una and greatly increases the discharge of the river. Waterfalls and tufa are rarer in this section, albeit still present. The confluence with the Sana marks the end of the middle section of the river and the beginning of the lower section. The total length of the river between Bihać and Novi Grad is around , with a gradient of 0.067% and drop of . Lower course The lower section of the river spans from the town of Novi Grad to the river mouth. After exiting the town of Novi Grad, the river flows in a general northeast direction until its confluence with the Sava river near Jasenovac. Major towns and villages on the river in this section are Novi Grad, Kostajnica and Kozarska Dubica on the right bank in Bosnia and Dvor na Uni, Hrvatska Kostajnica and Hrvatska Dubica on the left bank in Croatia. The waterfalls, rapids and tufa rock that were common in previous sections are almost completely nonexistent in the lower section as the Una takes up the characteristics of a mature river, meandering through alluvial plains and having a low gradient. Near its confluence with the Sava exist a couple of oxbow lakes colloquially called Stara Una (lit. "Old Una"). After a total length of about 212 km, the Una flows into the Sava river near the Croatian village of Jasenovac. The total length of the river between Novi Grad and Jasenovac is around , with a gradient of 0.041% and drop of . == Hydrography ==

Watershed The watershed of the Una river has a total area of , of which 79% () belongs to Bosnia and Herzegovina, and 21% () to Croatia. It borders the watersheds of the Korana, Glina and Sunja to the northwest, the Adriatic watersheds of the Lika, Zrmanja and Cetina to the southwest, the watershed of the Cetina to the south and the watersheds of the Vrbas and Jablanica to the east. The shape of the watershed itself is very irregular, but roughly triangular. Due to strong karst influence in the area, the watershed is poorly developed with few large surface streams. The karstification coefficient for the entire watershed is 0.244, which means that 24.4% of the surface area in the watershed lacks proper surface streams and drainage. The karstification coefficient up to Bihać is 0.43, up to Novi Grad 0.28 and up to Kostajnica 0.26. The watersheds of the Una and the watersheds of the Korana and Glina are often grouped together for analytical purposes in Bosnia and Herzegovina. Discharge The Una river has an average discharge of at its mouth, with a minimal discharge of . There are relatively small differences in the average monthly discharges (the driest month August has 37% of average yearly discharge while the wettest month April has 155%) and minimal daily and monthly discharges also show a very small difference. Low discharges last a relatively long time and high discharges appear quickly due to sudden rainfall and snowmelt and last a comparatively short amount of time. High discharges and water levels are present in April and December, and low discharges in August and January. There are multiple measuring stations in Bosnia and Herzegovina on the Una, and their data is show in the tables below == Tributaries ==

The Una river has a relatively weakly developed network of tributaries, owing to its karst geology. Most of the tributaries are shorter rivers, albeit with strong sources and relatively large discharges. There is also a number of karst springs located directly at the main channel of the river. The right tributaries of the river are the Krka, Unac, Krušnica, Vojskova and Sana rivers, and the left tributaries are the Dobrenica, Drobinica, Klokot and Baštra rivers. There are multiple measuring stations in Bosnia and Herzegovina on the Unac, and their data is show in the table below: Klokot The Klokot is a short river with watershed area of about 94 km2 and a length of 4.5 km. It flows out of a very strong karst spring around 5 – 6 km west of Bihać and has an average discharge of 14 – 15 m3/s. Krka The Krka is a right tributary of the Una, and, for the entirety of its length, forms the border between Bosnia and Croatia. It is long and forms a small canyon. It has a watershed area of 119 km2 and is part of the Una National Park. Krušnica The Krušnica is a right tributary of the Una. Its source, a strong karst spring with an average discharge of 7 – 8 m3/s, is located 6 km south of Bosanska Krupa. It is around long and has a watershed area of 301 km2. One interesting thing to note about the river itself is the fact that a small branch of the Una river flows into the Krušnica first, before the Krušnica flows into the Una. A small hydroelectric power plant is also located near the river source. File:Park prirode rijeka Sana - donji tok 2.jpg|The lower course of the Sana File:Fluss Unac in der Schlucht vor Martin Brod.JPG|The Unac before Martin Brod File:Klokot (Una).jpg|The Klokot in Bihać File:Krušnica - panoramio.jpg|The Krušnica near Bosanska Krupa == Economy ==

Hydropower Due to the rivers's steep gradient, especially in the upper course, 942 MW of electrical energy could be produced if all the potential energy of the watershed was used, and currently, less than 1% of the river's hydroelectric potential is put into use. There have been multiple hydropower projects drafted to use the potential energy of the rivers biggest waterfalls and canyons, but they were met with fierce resistance from the local and international communities due to fear of the destruction of the river's natural and cultural heritage. Currently, there are only three smaller hydroelectric powerplants in the river's watershed: the small Bihać and Krušnica hydroelectric plants, and the larger Una Kostela plant. The small Bihać hydroelectric power plant is located near the city center, with the machine room being located at the end of a intake channel, taking water from the river near the city park. It was constructed in 1912. during the Austro - Hungarian rule in Bosnia, together with the electrical network of the city. The old defensive moat of the city was deepened, widened and repurposed as an intake channel for the power plant, utilizing the natural drop of the river. In its original form, it contained two Francis turbines with an installed power of 87 kW each and was used to power the city's electrical lighting. Today, it contains one generator with a power of 160 kW and a yearly electricity production of 400 MWh. It has a hydraulic head of 2.6 m and an intake capacity of 9 m3/s. The water is directed into the intake by a low, concrete dam, colloquially called "beton" (bos. concrete), that doubles as a walkway and bathing site during low water levels. During high water levels, excess water flows over the dam forming a long waterfall. The power plant along with all other related structures was in 2011. declared to be a national monument of Bosnia and Herzegovina. The Krušnica hydroelectric powerplant is located near the source of the Krušnica river near Bosanska Krupa and was, like the Bihać power plant, build during the Austro-Hungarian rule in Bosnia, in 1911. It has an installed capacity of 460 kW and a yearly electricity production of 400 MWh. The installed capacity of each turbine is 2.35 MW for a grand total of 9.40 MW. Rafting Rafting is one of the most popular form of outdoor recreation in Bosnia and Herzegovina, and is important part of the national park offer for the river Una. Fly fishing and angling The river Una as well as the Unac are popular fly fishing grounds, and among the largest in Europe. An abundant ichthyofauna, rich in salmonid species, primarily grayling and brown trout, with the Una being also famous huchen destinations. Fly fishing and other angling methods are allowed only in certain sections and under strict rules and regulations of the national park services. This also applies on most tributaries, especially the Unac, Krušnica, and Klokot, while the Krka, like most of the Unac watercourse within the National Park, is completely excluded from all water and underwater activities. ==Flora and fauna==

Over 170 types of medicinal herbs grow by the Una River; a rare plant called Campanula unensis, the "Una bluebell", was named after the River Una's bright turquoise and green colors. Ichthyofauna Twenty eight (28) species of fish live in the Una river, the biggest of which is the huchen (mladica, Latin: Hucho hucho). The river is rich in salmonid fish species, where as the healthy population of endemic huchen, otherwise globally endangered, makes the river Una and its main tributary the Sana, one of Europe's primer habitats and spawning grounds. Other smaller tributaries are also important for this fish, as it enters smaller stream during spawning season to lay eggs. == Cities and towns ==

Bihać Bihać is the largest and most important city located on the banks of the Una river and is the administrative center of the Una-Sana Canton in the Federation of Bosnia and Herzegovina and is the center of the Bihać municipality itself. The city itself has a population of 39 690, and the municipality has a population of 56 261. The Una National Park is almost completely located in the Bihać municipality, along with some of the largest waterfalls, canyons, cascades and tourist attractions. Some of the settlements on the Una river in the Bihać municipality are Martin Brod, Kulen Vakuf, Lohovo, Ripač, Pritoka, Golubić and Ostrožac na Uni. The river enters the city from the south after having formed the large Ribićka otoka island. It continues to flow north towards the Alija Izetbegović bridge and passes by the Midžića jezero lake. The first cascade in the city is located at the end of the low concrete dam of the hydroelectric power plant. After flowing under the bridge, it continues to flow north where it forms the Gradska otoka island. The island is accessible by two pedestrian bridges connecting it to both banks of the river, and another pedestrian bridge connecting it to the smaller Amerikančevo island. After Gradska otoka island, the river splits into multiple smaller channels and forms multiple islands, some of which are private property and are connected to the mainland by bridges and some of which are wild, uninhabited islands. Two additional cascades are located in this stretch. After the individual channels combine, the water flows over a large, V-shaped cascade, after which the river splits into two channels again, forming another island. There are cascades on both sides of the island. The western one is a popular fishing and fly fishing spot and the location where the water flows out of the hydroelectric power plant, and the one on the eastern side is a popular bathing site. After the island, the river channels combine again and the water flows under the second large bridge in the city, the Bakšaiš bridge. After the bridge, the river forms multiple cascades before splitting into two channels again and forming the large Bakšaš island, after which the two channels combine again before forming another large set of river islands called Jotanovi otoci or simply Jotani. The last large cascades in the city are located here. After Jotani islands, the river flows under an old pedestrian bridge just before its confluence with the Klokot river. Bosanska Krupa Bosanska Krupa is the largest town in the Bosanska Krupa municipality in the Una-Sana Canton and the administrative center of said municipality. The town has a population of 10 196, and the municipality has a population of 25 545. Another large settlement on the banks of the river in the municipality is the town of Bosanska Otoka. Kozarska Dubica Novi Grad is the largest town in the Novi Grad municipality in Republika Srpska and the administrative center of said municipality. The town has a population of 10 544, and the municipality has a population of 21 524. The river enters the town from the west and after exiting the town continues to flow northeast. == Environmental issues ==

The Una river, with the quality of its waters, unique landscape, rare tufa deposits and waterfalls, rapids, river islands and other aesthetic, geomorphological, hydrological and biological characteristics represents a unique environment in need of protection. The largest current threats to the river and its ecosystem are pollution and proposed hydropower projects. Pollution The upper section of the river is, for now, still a relatively untouched and unpolluted part of the river. The main pre-war pollutants, such as the cellulose factory in Drvar and the glue factory in Srb, have stopped operating after the war, and as such the water quality is satisfactory. Currently there are still multiple locations where raw, untreated sewage still flows into the river, and a large part of the sewage system of some of the cities on the river was destroyed during the war, worsening the problem. A current problem is also the exploitation of forests on the river banks and the exploitation of sand and clay from the riverbed, which could lead to erosion that could affect the river basin and the river itself. The Unac river is prone to sudden increases of discharge and water level, which could also lead to additional erosion. Another large but often overlooked issue is the fact that there are multiple illegal landfills located in the watershed of the river, most notable in the Una-Sana canton. Some of the landfills are located directly above spring which feed directly into the river itself. To this date, there have been no solutions to the problem as the government of the Una-Sana canton is unable to properly organize and find a suitable location for a canton-level landfill. Hydropower projects There have been multiple hydropower projects proposed on the rivers itself and its tributaries, including the large Unac, Vrhpolje and Ključ hydroelectric power plants, and the smaller Štrbački buk power plant. There have also been multiple proposals for smaller mini hydroelectric power plants along the smaller tributaries, such as the Dobrenica. Some of those power plants, like the Unac power plant, would have large dams that would flood attractive canyons while other would divert a large portion of river's water to a machine room several kilometers downstream, leaving large parts of the riverbed dry. All of those proposals were met with fierce resistance from the local and international communities for fear of the destruction of the river's unique environment and, eventually, were cancelled. ==Gallery==

File:Vrelo Une.jpg|The spring of the Una File:Martin Brod – Veliki slap.jpg|The Una in Martin Brod File:Bridge over Una river in Kulen Vakuf.jpg|The Una in Kulen Vakuf File:Unamameapark2.jpg|The Štrbački Buk viewed from Croatia File:Bihać noću..jpg|The Una in Bihać at night File:Una bei Bihac.jpg|The Una river canyon File:Bosanska Krupa, mestecko na Une.jpg|The Una in Bosanska Krupa File:Rijeka Una - Novi Grad 21.jpg|The Una in Bosanski Novi File:Una Hrvatska Kostajnica 2.jpg|The Una in Hrvatska Kostajnica == References ==