Credit: Caroline Martin
On Thursday 20 August 2026, Luxembourg's Water Management Administration announced that swimming is once again permitted at the beaches of the Upper Sûre Lake and the Upper Weiswampach Lake, after cyanobacteria levels returned to safe levels.
According to the administration, the situation observed in recent weeks due to the proliferation of cyanobacteria, also known as blue-green algae, has returned to normal. The latest analyses confirmed that concentrations of toxins produced by the cyanobacteria had fallen to levels that no longer pose a health risk.
The authorities explained that lower temperatures and recent rainfall had led to a significant decline in cyanobacterial biomass. Monitoring carried out by the Luxembourg Institute of Science and Technology (LIST) also confirmed that the blooms had dissipated.
Based on the latest analysis results, the health alert concerning the presence of cyanobacteria and their toxins has therefore been lifted and swimming is once again authorised at the affected sites.
LIST will continue to monitor cyanobacteria levels. The current status of Luxembourg's official bathing sites can be consulted on the Water Management Administration’s website.
