said municipality. The town has a population of 10 120, and the municipality has a population of 27 115. The river enters the town from the southwest and after exiting the town continues to flow northeast. The confluence of the Una and its largest tributary, the Sana, is located in the town itself, and the town also divides the middle and lower portions of the river. Kostajnica Main articles: Kostajnica and Hrvatska Kostajnica Kostajnica and Hrvatska Kostajnica are two towns on opposing banks of the river, in Bosnia and Croatia respectively. 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 3 834, and the municipality has a population of 5 977. The river enters the towns from the west and after exiting the town continues to flow east. Hrvatska Kostajnica is the largest town in the Hrvatska Kostajnica municipality in the Sisačko-moslavačka županija and the administrative center of said municipality. The town has a population of 2 746. 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