Cyanobacteria risk persists in Nové Mlýny reservoirs, health officials warn swimmers

Regional health authorities continue to detect cyanobacteria (blue‑green algae) in lagoons 1 and 2 of the upper Nové Mlýny reservoirs near Břeclav in South Moravia. The water quality is rated at level 3 on a five‑point scale, indicating a potential health risk for pregnant women, people with allergies, children and individuals with weakened immunity. Swimmers are advised to shower after bathing and to avoid prolonged exposure.

Other natural bathing sites in the South Moravian region are reported as safe, including locations in Brno‑south, Bohuslavice, Kovalovice, the Brno dam bathing areas (Kozí horka, Osada, Rakovec, Rokle, Sokolské) and the Vranov beach on the Znojmo reservoir. Water quality can fluctuate with weather conditions, such as heat‑driven algal growth or low flow during dry periods, but no swimming bans have been issued this year.