The role of historical fishpond systems during recent flood events
Most of the large pond systems in the Czech Republic were built in 16th century. One of the most important fishpond systems is the one of the Třeboň basin (Třeboň fishpond system - TFS). It is situated in South Bohemia in the upper Lužnice watershed, but the whole system also includes the upper watershed in Austria. The system consists of almost 1000 fishponds with a total area of 7 500 ha. Retention capacity of fishponds is estimated to be as big as 50-70 mil. m3, but might be even 110-140 mil. m3 during extreme floods. The situation is then often beyond control and damage occurs, which deteriorates the fishponds' water management function. The largest is Rožmberk fishpond (480 ha), which stored 50-70 mil. m3 during the 2002 flood while its normal volume is about 5.5 mil. m3.
In order to ensure a satisfactory flood retention capacity of fishpond systems, proper maintenance of their technical equipment is necessary and emergency measures for the whole system should be added.