Biochemical oxygen demand in rivers (2007-2023)

The key indicators for oxygenation of water bodies are biochemical oxygen demand (BOD), which is the amount of oxygen needed by microorganisms for aerobic decomposition of organic matter. The indicator illustrates temporal trends of BOD concentration in rivers and can be used to illustrate geographical variations in current nutrient concentrations and temporal trends. Biochemical oxygen demand (BOD) is used to measure water quality. It refers to the amount of oxygen required by aerobic microorganisms to decompose organic substances in a water sample over a period of five days in the dark at 20°C (BOD5), measured as milligrams per litre (mg O2/L) and weighted by the number of measuring stations. High values of BOD5 are usually a sign of organic pollution, which affects the water quality. The cleanest rivers have BOD5 values of less than 1 mg O2/L, moderately and heavily polluted rivers show values ranging from 2 to 8 mg O2/L. Only complete series after inter/extrapolation are presented.