Credit: AGE
On Friday 13 June 2025, Luxembourg's Water Management Authority (AGE) announced that blue-green algae had been observed on the beaches of the Upper Sûre Lake, resulting in a swimming ban and the recommendation to avoid all water-based activities.
Certain species of cyanobacteria produce toxins that can pose a health risk for humans, aquatic fauna, pets and livestock. For people, different disorders of variable nature and intensity may occur related to contact, ingestion or inhalation of these toxins. These can include headaches, skin irritation and/or burns or nausea.
Given the health risks, a swimming ban has been imposed with immediate effect for the Upper Sûre Lake in accordance with the amended Grand Ducal Regulation of 19 May 19 2009, determining special protection measures and monitoring programmes for the condition of swimming waters.
Furthermore, the Water Management Authority, based on the assessment of the Health Directorate, recommends that the public:
- do not allow dogs and other pets to drink the water;
- avoid any contact with water;
- avoid all water activities (e.g. water sports, fishing);
- do not eat any caught fish.
The authorities noted that there is no risk associated with the consumption of drinking water from the Upper Sûre Lake as the raw water is withdrawn from a depth (25m) where the concentration of cyanobacteria is very low. The water treatment system in place eliminates the toxins produced by the cyanobacteria.
The current situation regarding the opening or closure of official bathing sites can be monitored on the Water Management Administration's website: www.waasser.lu.
