The safety control process is carefully regulated. A sterile vial, lowered into the water with a pole always at the exact same point of the water body, clearly illustrates the process of regular water quality checks in Bavarian lakes, which are conducted every few weeks. On the same day, the cooled vial of lake water is delivered to the laboratory of the Bavarian State Office for Health and Food Safety (LGL).
There, the obtained samples are studied in detail for the presence of intestinal bacteria that pose a potential threat to the health of vacationers. A detailed analysis for cyanobacteria is also carried out if there is the slightest suspicion of the appearance of blue-green algae capable of causing severe allergic reactions and toxic poisoning.
The majority of studied samples bring positive results, confirming the ecological stability of the region. According to official data from the LGL, 96 percent of checked natural sites in the federal state have good or excellent water quality. Specialists regularly check 375 bodies of water in Bavaria that are registered as official recreational areas in accordance with the strict standards of the European Union. These high indicators clearly testify to the effectiveness of long-term environmental protection programs implemented on the territory of the region.
A Lake in Munich Received an Unsatisfactory Rating
Nevertheless, in the course of monitoring, isolated exceptions were also recorded that require increased attention from environmental services. Two bathing spots at Lake Meerhofsee in the Lower Franconian town of Alzenau and one point at Lake Krebensee in Lower Franconia received a “satisfactory” rating.
In Munich, the northern shore of Lake Riemer See was recognized as unsatisfactory, which caused serious concern among local residents. At the same time, on the southern shore of the same body of water, the situation looks significantly better, where the water quality was able to obtain a “good” rating, which points to the purely local character of the arisen ecological difficulties.
Despite the identified deviations, the Municipality of Munich sees no objective reasons for introducing an immediate total ban on visiting Lake Riemer See. Experts explain the low final rating by a specific statistical method used to calculate long-term water quality.
For this purpose, after the completion of each bathing season, the measurement indicators for the current year and the three preceding years are retrospectively summed up. Thus, even a short-term failure recorded in the past continues to directly influence the current official status of the natural site.
City Authorities Attribute the Low Result to Waterfowl
The unsatisfactory rating of the northern shore of Lake Riemer See is due to two short-term pollutions, one of which occurred in 2023, and the second in 2024, the city administration reported. The main cause of this ecological incident was presumably waterfowl, whose excessive concentration on the lake negatively affected the overall water quality rating. Meanwhile, current samples of the lake water taken in 2025 and 2026 turned out to be completely within the norm, which confirms the natural self-purification of the body of water and the stability of its current condition.
Currently, municipal services are taking comprehensive measures, including the introduction of a strict ban on feeding birds by vacationers. In addition, coastal lawns are now mowed much more frequently so that bird droppings do not remain on the grass for too long and are not washed into the lake by rains. Also, special garbage bins protected from crows were installed around the body of water, which are emptied by special services more frequently than before, allowing for the complete minimization of the amount of food attractive to birds.
Bathing Ban at the Ebertshausener Weiher Pond
Many Bavarian lakes and ponds near which residents like to relax in the summer period do not figure in the LGL statistics at all, since they are not officially registered as bathing spots according to EU standards. Thus, although Lake Riemer See stands out with the worst rating in the official report, it is not the most polluted body of water in the region, as small local sites often remain outside the framework of European monitoring.
For example, warning signs are installed on the shore of the Ebertshausener Weiher pond in the municipality of Odelzhausen, calling to completely refrain from bathing in the water. They state: “Attention, blue-green algae! Danger to the health of humans and animals! Bathing in this body of water is prohibited.” This case clearly demonstrates that the real ecological risks at unofficial sites can be significantly higher.
Burgomaster Markus Trinkl observes the development of the situation with deep anxiety, as this site has important significance for the local community. He reported that he has occupied this post already for 12 years, and over recent years, the water quality in the Ebertshausener Weiher pond has significantly deteriorated. In the current year, already the first scheduled measurement showed such high parameters of bacteriological and algal pollution that a ban on bathing in this pond is forcedly being introduced for the entire summer season.
(The burgomaster forgot, apparently, that his job is not to monitor problems, but to prevent their occurrence and solve the community’s problems. And the fact that he has headed the local community for 12 years already raises many questions for the burgomaster — Ed.)
Beavers, Agriculture, and Climate Changes Contribute to the Spread of Blue-Green Algae
The reasons for the rapid spread of blue-green algae, especially in the last five years, according to Trinkl, are of a complex nature and reflect general changes in the local ecosystem. On the one hand, the pond has a fairly large area, but at the same time, it has only one small tributary. This tributary completely fails to provide the necessary volume of water exchange that is required for the constant influx of a sufficient amount of fresh running water. As key sources of local problems, Trinkl also names the intensive influence from agriculture and the increased activity of beavers, who undermine the soil on the shore, contributing to the silting of the bottom. Global climate changes play a role that is not the least significant either, as the average water temperature in the summer months has noticeably increased, creating ideal conditions for the reproduction of bacteria.
(Of course, because for bad dancers, beavers and global warming get in the way — Ed.)
For a radical improvement of the situation, the local community has several ideas. Currently, such radical measures as a complete technical drainage of the water and deep mechanical treatment of the silt are being considered. Now this project, standard for lake cleaning, is being studied in detail jointly with specialized ecological and engineering services. For the residents of Odelzhausen, this pond is the only accessible spot for recreation in the water. However, the burgomaster cannot guarantee that the body of water will ever again become the safe and popular meeting place for vacationers that it was during the times of his youth. (At least while he is in power — Ed.)
