Algae-covered Traisen still draws Frequency festival guests

Low water levels and extensive algae growth have changed the appearance of the Traisen river, a popular cooling spot for visitors to the FM4 Frequency Festival in St. Pölten, ORF reports.

The river runs between the festival campsite and grounds, where many guests cool off or sit with their feet in the water. Visitors have reported heavy algae growth and, in some places, a smell of fish, but the long dry period and high temperatures have not deterred them.

Swimming in the Traisen is generally permitted, city spokesman Thomas Kainz told ORF. As a public body of water, the river may be used under the rules of common use and at visitors’ own risk.

The city has asked festivalgoers not to pour drinks such as beer or wine spritzers into the river, and not to dispose of rubbish or other liquids there. Urinating and showering in the water should also be avoided. The city recommends using sunscreen that is as water and environmentally friendly as possible before entering the river.

The city does not expect the festival to cause a lasting deterioration in water quality. Measurements taken during the 2025 Frequency Festival were well below the permitted limits, while Lower Austria’s water monitoring authority found no excessive pollution. The city spokesman said this year’s quality targets were also not expected to be exceeded.

Measures have also been taken to protect fish. Because water levels are low, additional water is being channelled into the Traisen from industrial channels to help improve water temperature, oxygen levels and habitat conditions.

An oil barrier has been installed downstream from the festival grounds to intercept rubbish. The waste is removed and disposed of regularly. After cleaning work is completed, authorities plan to carry out their usual final inspection of the river.