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Human intervention has shortened the length of the Danube by 134 kilometers in the past two centuries, the researchers said in a study published Tuesday.
According to the riverbed investigation published by the Bavarian Provincial Office, since the 19th century, the Danube has not only been shorter than its original length, but also 40 percent narrower. The changes were caused by human interventions such as the removal of meanders from rivers, flood protection interventions and the construction of dams.
The research also found that, as a result of human interventions, the flooding in the river does not reach the Danube Delta, but is deposited in the riverbed, which permanently changes the quality of the water.
The research was conducted to determine the adverse effects of human intervention and to suggest measures to remedy it.
Previously, 40-60 million tons of sediment reached the Black Sea each year, but now only 15-20 million tons. The sediment is deposited along the river bed. A third of the entire section of the river is affected by sediment deposition, mainly in areas in front of hydroelectric plants. Behind the dams that belong to the power plants, there is a total lack of sediment, which means that the river bed often deepens there, experts explained.
To restore the sediment home, the researchers proposed different methods to retrieve the deposited sediment from the water. Such a measure could be the removal of the riverfront fortifications or the construction of modern hydroelectric power plants. Agriculture, in turn, could contribute to improving the level of alluvium in the Danube through erosion mitigation measures.
The project, largely funded by the European Union, involved 14 institutions from 9 countries in the Danube region (Hungary, Austria, Bulgaria, Slovenia, Slovakia, Germany, Romania, Croatia, Serbia) and analyzed river sediment for three years.
The Danube is now officially 2,857 km long, the second longest river in Europe after the Volga, which was still almost 3,000 km in the 19th century. Currently only a tenth is in an “almost natural state” according to the Bavarian authorities.
MTI, image: Ivándi Szabó Balázs / 24.hu
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