The activities of over 80 million people in 19 countries have an impact on the natural environment of the Danube River Basin, and are also leading to serious problems with water quality and quantity, as well as significant reductions in biodiversity in certain parts of the river basin.
Too much inadequately treated waste water still ends up in the Danube, leaving at risk the drinking water supply for millions of people, while also leading to problems for irrigation, industry, fishing, and tourism.
The main pollution problem is the excessive volumes of nutrients entering the river, mainly from agricultural fertilisers, and untreated or not adequately treated municipal sewage, including faeces and household products.
Further, organic pollution can cause significant changes in the oxygen balance of rivers and lakes. Consequently, this can impact the composition of aquatic species. Organic pollution is mainly caused by untreated or only partially treated wastewater from cities/villages, industry and agriculture. Many agglomerations in the Danube River Basin have none, or insufficient, wastewater treatment and are therefore key contributors to organic pollution.
Hazardous and toxic substances are also a major threat, made worse by occasional industrial accidents or floods when deadly toxins may be flushed directly into watercourses.
A recent analysis also shows that surface waters suffer significantly from hydromorphological alterations. Interruption of river and habitat continuity, disconnection of adjacent wetland/floodplains, hydrological alterations and future infrastructure may impact water status and therefore need to be addressed in future.
It is assumed that the effects of the floods that impacted the countries in the Danube basin in the last years were worsened due to deforestation, the destruction of natural floodplains and human-induced global warming.
Preserving the natural habitats of the many species living in the basin is a constant struggle. The habitats of pelicans in the Danube Delta and sturgeon species are particularly under threat.
Major problems affecting aquatic ecosystems in the Danube River Basin
- Excessive nutrient loads (particularly nitrogen and phosphorous)
- High amounts of organic substances originating from untreated or poorly treated wastewater
- Changes in river flow patterns (hydromorphological alterations) and its effect on sediment transportation
- Contamination with hazardous substances (including heavy metals, oil, and microbiological toxins)
- Accidental pollution from contaminated sites or waste disposal, as well as from navigation
- Degradation and loss of wetlands
Human pressures and impacts are investigated and addressed in the frame of the Danube River Basin Management Plan (according to the WFD).
Water quality in the Danube River Basin is largely influenced by the inputs of pollutants - particularly excessive nutrients, organic material, and hazardous substances. According to the ICPDR’s Emission Inventory 2002, which considers point and diffuse sources of pollution in the whole Danube River Basin, municipalities and industry released fewer pollutants than in previous years.
Since the 16th century, people have been changing the natural course of the rivers in the Danube River Basin, mainly for flood defence, hydropower generation and navigation. All these changes affect the ecological quality of the rivers. Changes in the depth or width of a river typically reduce flow rates, interrupting natural sediment transportation as well as the migration routes of animals.
Article in Danube Watch 02/2006