Water quality in Czech ponds is deteriorating, mainly due to drought and climate change. Rainfall is the same as in the past, but evaporation is much higher. The construction of wastewater treatment plants in smaller settlements has also become a major problem in recent years. Photo credit: MENDELU
Czech Republic, June 14 (BD) – “The annual rainfall is approximately the same, but often unevenly distributed, with long dry periods and heavy, often torrential rainfall. The way in which fields are farmed, soil compaction, large soil units, and ploughing up to the edge of the pond’s water surface all play a part. All this increases the erosion of topsoil, which ends up in the sediments of the ponds and reduces their water capacity,” said Radovan Kopp from the Institute of Zoology, Fisheries, Hydrobiology and Apiculture at Mendel University.
While rainfall has remained the same, evaporation has increased substantially. Few people can imagine that on sunny summer days three litres of water evaporate from a hectare of water in a single second. The total volume of water thus decreases rapidly; temperatures rise, decomposition processes in pond sediments accelerate, the dissolved oxygen content decreases and the whole pond ecosystem becomes highly unstable.
Especially in South Moravia, which has long been one of the driest areas of the Czech Republic, so-called rescue fishing in the summer months has become quite common. Fishermen assess critical parameters and catch fish as a precautionary measure to prevent them from dying. Some of the water areas that were commonly managed a few years ago have even dried up completely.
In recent years, the construction of wastewater treatment plants (WWTPs) in smaller municipalities with populations below 2,000 has also become a major problem. These small plants are not limited by legislation in terms of removal or even monitoring of phosphorus in the runoff. A newly built WWTP will improve water quality in terms of organic pollution, but will add phosphorus to the runoff.
The general public usually attributes the poor water quality of the ponds to the intensity of fishing. In most cases, if fishermen do not fertilise the ponds but simply feed the fish with cereals, their phosphorus input to the pond is lower than the amount of phosphorus they ‘extract’ from the pond in the form of fish caught. Even in the case of partial fertilisation of the pond, the main source of phosphorus is from dewatered wastewater and sewage water.
“Unless we start to address the issue of wastewater and the quality of the “treated” wastewater intensively, there will be no improvement of the current situation and the water quality in the ponds will further deteriorate in conditions of rising temperatures. The idea of clear, swimmable bodies of water is thus an illusion under current conditions, even if fishing is completely excluded,” Kopp added.
