Where the current has made shortcuts, the old river-beds no longer expect regular flow of water. Usually the exchange of water in some of the younger oxbow lakes takes place mostly during the spring floods, bringing fresh water. Due to the specific hydrologic conditions special communities of flora and fauna have developed in the oxbow lakes, which is why these are often in the status of protected habitats interesting to nature watchers. Oxbow lakes are often „controlled“ by beavers leaving their traces on the banks thereof.