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BOD

In European rivers, BOD levels have generally been decreasing between 1992 and 2020 (Figure 1a), with an average annual decrease in BOD of 0.06 mg/l (0.7% per year). The BOD reached its lowest level (2.4 mg/l) in 2010 and has only surpassed 3.0 mg/l once since then (in 2015). A significant decrease is evident at 44% of the river sites, with an additional 7% of the rivers having a marginally decreasing trend. A significantly increasing BOD trend is recorded at 12% of the sites.