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Improved water quality in the Rhine and Elbe Rivers

Source: UBA 2010: Water resource management in Germany, part 1 fundamentals p. 54-57

The assessment of oxygen conditions in watercourses in Germany now occurs within the framework of ecological status monitoring. In the past, organic pressures were determined according to the Saprobic System, the results of which have been published every five years since 1975 by LAWA in the form of a biological water quality map. The Saprobic System uses macrozoobenthos (= invertebrates visible to the naked eye which live on or in the river bed) to describe the oxygen balance of a watercourse.

Observations of the biotic communities and oxygen balance in waterbodies have been recorded since at least the beginning of the last century. Figure 29 illustrates the conditions in the German sections of the Rhine and Elbe rivers. According to species lists from various authors, in the early 20th century the Rhine was inhabited by some 165 species of macrozoobenthos, while in around 1930 the Elbe was inhabited by around 120 species. As wastewater pollution increased and oxygen levels fell, the numbers of species have declined dramatically since the mid-1950s. The aquatic insect species (mayflies, stoneflies and caddis flies) have been particularly hard-hit by this development. By 1971, only 5 species out of a total of more than 100 remained in the Rhine, and in the Elbe only a few more. Improved oxygen conditions associated with the construction of industrial and municipal sewage treatment plants in the Rhine led to a turnaround from the mid-1970s onwards, while in the Elbe the situation did not improve until after German reunification in the early 1990s. Some of the characteristic river species that had been considered extinct or heavily decimated have now returned, but a large number of typical species remain absent, no doubt partly due to the fact that their habitats no longer exist due to structural impoverishment. Additionally, large numbers of non-native and ubiquitous species (species with a high degree of adaptability) which are better able to withstand anthropogenic