All-clear in Kallmünz: Naab water free of blue-green algae!

All-clear in Kallmünz: Naab water free of blue-green algae!

On September 4, 2025, the water management office gave the all-clear regarding blue-green algae in the Naab near Kallmünz. The latest water sample showed no evidence of these harmful organisms, which is reassuring news for both residents and bathers. This all-clear follows a critical situation in 2022, when an increase in blue-green algae was detected in the Naab, extending from Kallmünz to Etterzhausen.

At this time, on August 5, 2022, the Regensburg Water Management Office informed the district office about the increasing blue-green algae populations in the water. These microorganisms can cause health problems including skin irritation, nausea, vomiting or diarrhea. At that time, the health department for the city and district of Regensburg strongly advised against swimming in the affected sections of the Naab.

Health risks from blue-green algae

Blue-green algae, also known as cyanobacteria, can occur in high concentrations in stagnant or slow-moving water. The risks for bathers are particularly increased in very warm summers. According to that Federal Environment Agency These organisms can cause serious damage to the liver, kidneys and nerves by releasing cyanotoxins, especially in small children and primary school children, who are particularly at risk.

The measurement and monitoring of cyanobacteria is carried out as part of bathing water monitoring, with remote sensing methods being a suitable method. These technologies, including satellite imagery, enable the detection and analysis of blue-green algae blooms and play a critical role in the governance system to ensure water quality.

Precautions for the future

In order to minimize health risks, the responsible authorities have already initiated measures to reduce nutrient inputs into water bodies. High phosphorus concentrations are a main cause of the mass growth of cyanobacteria in water bodies. Long-term efforts aim to reduce these levels below the critical threshold of 30 µg total phosphate per liter to limit the growth of blue-green algae.

The current all-clear is seen as a positive signal for residents and bathers in Kallmünz and the surrounding area. The final tests show that the waters are temporarily safe, but continued monitoring remains essential to avoid health risks during the swimming season.