These water bodies are more susceptible to short-term pollution events linked to heavy rainfall or drought, particularly during summer.
Pretty much all of Europe is going to have combined sewers somewhere. If you have combined sewers, you’re gonna have raw sewage in your waterways if you get enough rain.
Combined sewers can cause serious water pollution problems during combined sewer overflow (CSO) events when combined sewage and surface runoff flows exceed the capacity of the sewage treatment plant, or of the maximum flow rate of the system which transmits the combined sources. In instances where exceptionally high surface runoff occurs (such as large rainstorms), the load on individual tributary branches of the sewer system may cause a back-up to a point where raw sewage flows out of input sources such as toilets, causing inhabited buildings to be flooded with a toxic sewage-runoff mixture, incurring costs for cleanup and repair. When combined sewer systems experience these higher than normal throughputs, relief systems cause discharges containing human and industrial waste to flow into rivers, streams, or other bodies of water.
It’s expensive to replace those, so I’d expect them to be around to some extent until sewer systems need to be replaced.
Pretty much all of Europe is going to have combined sewers somewhere. If you have combined sewers, you’re gonna have raw sewage in your waterways if you get enough rain.
https://en.wikipedia.org/wiki/Combined_sewer
It’s expensive to replace those, so I’d expect them to be around to some extent until sewer systems need to be replaced.