The formation and evolution of the Csicsó oxbow lake (Žitný ostrov, Slovakia – land use and wetland habitat changes

Abstract

The landscape-structural importance and conservation value of the oxbow lakes are demonstrated by the example of the Csicsó oxbow lake, situated at the SE part of the Ωitny Ostrov, Slovakia. This present oxbow and its former anabranch are very young from hydrological point of view. It can be precisely derived from the map sheets of the first and second military surveys of the Habsburg Empire, that this anabranch has been originally formed between 1786 and 1822. The reach has been practically cut off from the river at the end of the 19th century but remained on the floodway of the Danube during the early water control works. Regular water supply reached the oxbow more than once a year in this phase. As a result of the construction of the new flood control levee system after the WWII, the oxbow is now on the flood-free side of the dykes (former floodplain), so the regular inundation and water supply from the river has been stopped. As an internationally important habitat, the protected Csicsó oxbow was declared as ’Ramsar area’ in 1993. We surveyed the animal and plant species of the oxbow and its surroundings. These species are mostly endangered, protected and have European importance. The occurrence of the very rare Mud-Minnow (Umbra kramer) should be mentioned. We estimated the degradation and regeneration time of the different habitats based on our present and past investigations and literature data as well. The main output of this is that the degradation is always quicker in time that the regeneration. The ecological water demand, needed maintaining of the habitats, is also estimated in form of the required water cover and groundwater table level. Furthermore, the habitat map, characterised by the vegetation, is also presented.