As you have seen, water characteristics can give you a lot of information about the ecological state of a river. However, ecological status concerns also living organisms.

These organisms are called indicator organisms. Some of them can survive in polluted waters. Thus, its presence will indicate a high level of water pollution. On the other hand, some of these organisms can only live in clean water. Thus, if we find them, we will know that the water is not polluted.

Know your river