Natural, artificial and heavily modified

Even though, for reasons inherent to their use, many constructions must be maintained, the water bodies concerned should be ecologically revalued to the greatest possible extent: at least the best possible status permitted by the existing uses should be achieved. This is true of considerably modified water bodies – almost the entire Rhine and all of its most important tributaries – as well as of artificial water bodies such as channels or flooded gravel pits. Only the R. Sieg and the upper reaches of Neckar, Main, Moselle, Saar, Ruhr, Lippe and Vechte are largely still natural.