Swimming Banned in Upper Sûre, Weiswampach Lakes Due to Blue Algae

On Friday 8 September 2023, Luxembourg's Water Management Authority announced that blue-green algae has been observed on the beaches of the Upper Sûre Lake and in the lakes located in Weiswampach, resulting in a swimming ban and the recommendation to avoid all nautical 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.

The analyses from 8 September 2023 revealed the presence of toxic cyanobacteria in the Upper Sûre Lake and in the Weiswampach lakes, with an overrun of the safety threshold in microcystins. Given the health risks, a swimming ban was pronounced with immediate effect for the lakes in question, in accordance with the amended Grand-Ducal regulation of 19 May 2009 determining the special protection measures and the monitoring programmes for the state of swimming waters.

Anyone experiencing health problems following swimming in the Upper Sûre lake and in the Weiswampach lakes during the past few days, is advised to contact their doctor, mentioning any possible contact with toxic cyanobacteria.

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.

With regard to the lake of Echternach, swimming remains, at this stage, authorised. Any possible prohibition concerning this site will be announced to the public.

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that there is no risk associated with the consumption of drinking water from the Upper Sûre Lake as the raw water is withdrawn from a depth (25m) where the concentration of cyanobacteria is very low.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 concerning bathing waters (the Upper Sûre Lake, the Weiswampach lake,  the Echternach lake and the Remerschen ponds) can be followed online at www.waasser.lu. Leaflets on the subject of cyanobacteria can also be downloaded there.