Hundreds of dead fish found in Jeziorka river, Piaseczno warns residents to stay out of water
Hundreds of dead fish were discovered in the Jeziorka river in Piaseczno on Friday, prompting authorities to warn residents against entering the water. Initial tests point to oxygen depletion caused by the recent heatwave, not a sewage leak.
Discovery and cleanup
On Friday, 3 July, residents and authorities in Piaseczno, a town south of Warsaw, spotted a large number of dead fish in the Jeziorka river. The worst affected stretch was near ulica Dworska. The Municipal Crisis Management Team immediately notified relevant services. Two fire brigade units were dispatched to assist workers from Państwowe Gospodarstwo Wodne Wody Polskie (Polish Waters) in removing the dead fish from the riverbed. The cleanup operation lasted several hours, with crews working to limit the environmental and public nuisance.
On Friday, 3 July, a large number of dead fish were observed in the Jeziorka, mainly in the area of ul. Dworska. Water and fish samples were taken for analysis by the Voivodeship Inspectorate for Environmental Protection and Polish Waters.
Cause investigation
Samples of water and dead fish were immediately sent to laboratories. The Voivodeship Inspectorate for Environmental Protection and Polish Waters are conducting detailed tests to determine the exact cause of the fish kill. Authorities have already ruled out a malfunction or uncontrolled discharge from the nearby sewage treatment plant in Wólka Kozodawska. According to the town hall, nothing indicates a link to the plant.
The most likely explanation, officials say, is przyducha, a sudden drop in dissolved oxygen levels triggered by the extreme heatwave that has persisted in recent days. Przyducha occurs when high temperatures and low water flow reduce oxygen content, often suffocating aquatic life. The municipality stated that the phenomenon is consistent with the weather conditions.
According to current findings, no unusual discharge from the sewage treatment plant was recorded. It is probable that the fish kill is the result of so-called przyducha, a significant drop in oxygen content in the water caused by extreme heat.
Public safety warning
While laboratory results are pending, the local government issued an urgent appeal to residents. People are asked to avoid entering the Jeziorka and any other water bodies in the Piaseczno municipality, including the ponds at Górki Szymona. Dog owners are specifically told not to let their pets into the water. The warning, disseminated via social media and official channels, covers all rivers, ponds, and other water bodies in the area.
Until the situation regarding the fish kill in the Jeziorka is clarified, we appeal not to enter or allow animals into water bodies, rivers, and ponds in the Piaseczno municipality. This applies primarily to the Jeziorka and Górki Szymona.
Ongoing response
The cleanup of the riverbed continues to prevent further deterioration and reduce odour. The municipality’s crisis management team is monitoring the situation. Definitive answers will come from the laboratory analyses currently underway. Authorities have not provided a timeline for the results.
