Algae plague in the Aachener Weiher: City fights for clear water!

Algae plague in the Aachener Weiher: City fights for clear water!

The algae plague at the Aachener Weiher in Cologne poses a challenge for the city. A worrying trend has emerged, particularly during hot days: thick carpets of algae spread across the surface of the water, reaching deep below the surface. This situation is not only disturbing to look at, but can also be smelled in the areas near the bank. The water in the pond is not of drinking water quality anyway, which makes the matter even more explosive. According to the Express The algae fields are clearly visible from Hiroshima-Nagasaki Park and are causing concern among walkers and residents.

The Cologne City Drainage Company (StEB) is responsible for the water quality of the pond. They recently struggled with a broken mowing boat used to combat the algae population. Spokeswoman Birgit Konopatzki announced that the mowing boat will be back in use on July 1, 2025 and is now diligently removing aquatic plant remains. The first improvements to the water surface are expected to occur within a few days, although the current heat wave could stimulate algae growth in the short term. Even if the oxygen content in the water is rated as good at 15 mg/l, the algae put a strain on the entire ecology of the pond.

Measures to combat algae

In addition to the measures of the mowing boat, the inflow of fresh water is increased by an installed standpipe. This should help to ensure water quality in the long term. But the situation remains tense: a lower water level and dense vegetation put the mowing boat at high risk, as the screw has already been damaged twice. This clearly shows that it is not an easy task to stop this annoying algae plague.

In times like these, it also becomes important to look beyond Cologne's city limits. The problem of harmful algae blooms (HABs) concerns many communities in Germany and beyond. Loud Robeco There is a growing threat to water quality from algae blooms that are exceeding the capacity of many drinking water utilities. Investments in modern water treatment systems and technologies to detect and destroy cyanotoxin cells are becoming increasingly urgent.

The problems at Aachener Weiher are part of a larger issue that affects us all. Communities increasingly see themselves as having a duty to find suitable solutions to protect the quality and quantity of water. It remains to be hoped that the progress in combating the algae plague in Cologne is not just a temporary flare-up, but rather the beginning of lasting changes in water management and care.