Nové Mlýny reservoirs face ongoing cyanobacteria crisis as water release deemed unsafe

The director of the Morava River Basin Authority, Antonín Tůma, said releasing water from the Nové Mlýny reservoirs is technically and safety-wise impossible, as it would compromise flood‑control and water‑management functions. Experts link the problem to high temperatures, low river flows and excessive nutrients, which fuel massive cyanobacteria blooms that deplete oxygen and cause fish kills. Recent water exchange has modestly improved oxygen levels, but the situation remains classified as risky. Fish mortality this week reached about half a tonne to 1.5 tonnes, adding to the roughly 40 tonnes lost in 2022. Authorities continue to release only the maximum permitted volume from the reservoirs, monitor the river segment with drones, and consider options such as flushing the Dyje or converting stagnant zones into flowing water or wetland habitats to curb algal growth.