Credit: AGE

On Thursday 21 September 2023, Luxembourg's Water Management Authority announced that the swimming ban concerning the Upper Sûre Lake has been lifted.

According to the authority, seasonal changes in the climatology and hydrodynamics of the Upper Sûre Lake have led to a strong decline in the biomass of cyanobacteria and the dissipation of blue algae blooms. Recent analyses carried out by the Luxembourg Institute of Science and Technology (LIST) have shown that the concentrations of cyanotoxins which can pose health risks for humans and animals have also fallen considerably.

This development in the situation puts an end to the alert for microbiological and toxic risks at the public health level linked to the presence of cyanobacteria blooms. The recreational and sporting activities can therefore resume.

In this context, the Water Management Authority emphasised that, in accordance with the provisions of the amended Grand-Ducal regulation of 19 May 2009, the bathing season will end on 30 September 2023.

The current situation regarding the opening or closing of official swimming sites can be followed online at and at