Special Nature Reserve Kraljevac is situated in the area where the Pannonian Sea once lay, where winds formed loess slopes and the springs Spasovina and Obzovik and the Mramorak and Kraljevac rivers cut vast valleys through river erosion in the past. This watercourse was transformed into a lake when a dam and embankments were built in 1983. This transformation caused the water table to rise and flood the surrounding alluvial forests and fields, as well as the separation of peat from the bottom of lake and formation of floating and permanently anchored islands.
In 2003, following a conservation initiative by the Sport Fishing Association Deliblatsko Jezero, from Deliblato, the Institute for Nature Conservation Vojvodina Province issued the Proposal for Beforehand Protection of the Wetland Kraljevac with Vašarište and Obzovik (Official Gazette No. 112/2003). In 2006, the protected area together with the Special Nature Reserve Deliblatska Peščara, forming one biogeographic region, were included in the Pan-European Emerald Ecological Network based on the Bern Convention on Conservation of European Wild Flora and Fauna and Natural Habitats (Resolutions No. 4 and 6). In 2009, following the decision of the Government of the Republic of Serbia, the Special Nature Reserve Kraljevac was declared “the first category protected area of greatest national importance,” (Official Gazette No. 110/2009). The Sport Fishing Association Deliblatsko Jezero was nominated a custodian of the Reserve to protect and maintain order in the Reserve and organize the Park Ranger Service.