Rommwiss beach / Upper Sûre Lake; Credit: AGE

Luxembourg's Water Management Authority has announced that swimming is currently prohibited at Rommwiss beach in Boulaide due to the presence of blue algae.

As part of regular monitoring of the quality of bathing water, a significant proliferation of cyanobacteria, also known as "blue algae", was discovered in the Upper Sûre Lake, near Rommwiss beach.

Given the health risks, the authorities have issued a swimming ban with immediate effect for Rommwiss beach in accordance with the 2009 amended Grand Ducal regulation determining special protection measures and monitoring programmes for the state of bathing waters.

The Water Management Authority noted that certain species of cyanobacteria produce toxins which can pose a health risk for humans, aquatic fauna, domestic animals and livestock. As a result, the Luxembourg Institute of Science and Technology (LIST) was mandated to monitor cyanobacteria in bathing water in the Grand Duchy. These analyses revealed the presence of species of cyanobacteria potentially producing toxins and therefore potentially harmful to health.

Symptoms of illness linked to contact, ingestion or inhalation of these substances vary in nature and intensity but can for example include headaches, skin irritations and/or burns or even nausea. Anyone who experiences health problems after swimming is advised to contact their GP, mentioning possible contact with toxic cyanobacteria.

For water bodies in which a significant proliferation of cyanobacteria has been noted, the Water Management Authority (based on the assessment of the Health Directorate), has recommended that the public:

- do not let dogs or other domestic animals drink the water;
- avoid any contact with the water;
- avoid any water activities (e.g. water sports, fishing).

Especially when fishing, people should:

- avoid contact with fish;
- not consume caught fish;
- abandon fishing activity if cyanobacteria blooms are visible.

Any observation of blue algae in Luxembourg can be reported via the "Bloomin'Algae" app and will be assessed by a LIST expert. All reports can be viewed on

At present, swimming remains authorised on the other beaches of the Upper Sûre Lake, although the Water Management Authority recalled that the bathing season will end on Saturday 30 September 2023.