Summary:

It is known that carp ponds significantly affect the quality of surface waters, probably not polluting a water-course during regular production period but only during period of catches or during lowering of ponds. A study on physical and chemical properties of water in one of the Western Pomeranian rivers, the Krąpiel, was undertaken to verify this opinion. More than 200 ha complex of ponds is located in the catchment area of that river, in the settlement of Dzwonowo. The research was done monthly from April 2005 till April 2006. It was shown that lowering of the ponds causes the increase of nutrients, organic matter, and total suspended matter, but also negatively affects water quality. Pollutants however do not influence the increase of eutrophication processes and the river still retains self-purification ability.