Area: 360 ha
Legal declaration by Decree No. 2/1976. OTvH
Biogeographic region: Lower Danube Region
Encircled by the settlements of Dunapataj, Kalocsa, Miske and Hajós, the Kalocsa Plain contains some natural, mostly filled-up, semi-circular oxbows with rather regular contour. Only one of them contains water on a permanent basis; this is Lake Szelidi. The lake is 5 km long, 150-200 m wide and 3-4 m deep; its surface area is approx. 80 ha. Its southern shore is made up of a flat and forested sand dune, the so called “Castle Hill”, which is an important archaeological site. Three thousand years old urns and other artefacts from the Migration Period and the time of the Hungarian conquest of the Carpathian Basin were found here and then transported to the Hungarian National Museum.
The chemical composition of the lake is unique in Hungary, it contains sodium carbonate, magnesium salts and sodium iodide; the total salt content is approximately 4%. The lake is rich in microorganisms; a total of 29 Blue-green Alga species occurs here, among which four species are not known to occur anywhere else.
The importance of Lake Szelidi in the region is three-fold, as it is a popular holiday destination, an important lake for anglers and also has an important role in nature conservation. The aim of conservation is to preserve the unique alga flora of the lake and the vegetation of the shoreline and the adjacent areas. The pastures bordering the lake in the north are home to some endemic species of saline grasslands (e.g. Aster tripolium and Puccinellia limosa) and playas (e.g. Sueda pannonica). Streaming water that used to supply the lake is nowadays released to neighbouring grasslands before letting it enter the lake. This contributed to the increase of the bird populations of lake and its surroundings. The narrow reedy shorelines have always been rich in songbirds but as a result of the rewetting of the surrounding areas, large numbers of shorebirds and ducks have also started to frequent the reserve.