This map shows the mean annual concentrations of BOD (Biochemical oxygen demand) measured at Eionet-Water River monitoring stations from 1992 till 2011. All data are annual means. The purpose of the map is to provide an overview of the annual concentrations of BOD in rivers across Europe and to enable viewer to make comparisons of the values in European countries, River basin districts or in individual monitoring sites. BOD (Biological - or biochemical - Oxygen Demand) refers to the amount of organic matter present in water that will consume oxygen as it is decomposed by micro-organisms. BOD is commonly used for 5-day BOD (BOD5); for those Member States reporting 7-day BOD (BOD7), these values have been converted to BOD5 (BOD7 = 1.16 BOD5) for reasons of comparability.Large quantities of organic matter (microbes and decaying organic waste) in water are a potential risk to aquatic ecosystems and human health. A reduction in the amount of oxygen in water as a result of the decomposition of organic matter can endanger aquatic life through asphyxiation and disrupt the ecological balance of the water. It can also pollute water used for drinking and bathing. High levels of BOD can indicate such pollution.
In less detailed scale, data is aggregated by country and pie charts are displayed. In more detailed scale individual stations appear in shape of triangles. Historical data (from 1992 on) can be displayed and viewed with time slider tool.