A study by German scientists has established that global warming is the likely cause of chronic water shortages in the river Elbe, and that they threaten to bring shipping to a standstill along one of the continent's main inland waterways.
The study by the Institute of Climate Impact Research in the east German city of Potsdam is the result of six decades of continuous observation of water levels on the Elbe, which runs from the Czech Republic to the North Sea at Hamburg.
The scientists found that water levels had dropped so much during the past two decades that they had rendered the waterway impassable for barge traffic for periods of between four and six months in 1991, 1992, 2000 and 2003. Dr Frank Wechsung, who compiled the study, said: "If this trend continues, we can expect more frequent and more extremely low water levels on the river, which will make it even more difficult to use as a shipping route."
The institute's study says that the cause is lack of rain during the summer which has been induced by global warming. The scientists found that rainwater was not filling the Elbe as reliably as it did in the period 1950-1980, and that mean temperatures had increased in the region by 1C over the past 50 years.
Over the past 30 years there had been an average of 123 days when no rain fell in the Elbe region, whereas during the preceding 30 years, there had been only 85 days without rain.
"Even if we assume that rainfall stays at its present level, it is still certain that temperatures will increase," Dr Wechsung said. "This means that moisture in the drainage areas which feed the Elbe will dry up before it reaches the river. But there is a high possibility that there will be even less summer rainfall in future," he added.
The institute's findings coincide with an extensive German government improvement programme for the Elbe, which aims to increase its use as a thoroughfare for commercial barge traffic. German environmental groups say that it will lead to the destruction of marshlands which are home to rare plants, birds and mammals.
"The latest findings about dropping Elbe water levels make it clear that the government's plans to develop the river are complete nonsense because there will not be enough water under the keels of commercial vessels," said Paul Doerfler of the German environment association, Bund.
German environmentalists have urged the government to drop its plans and concentrate instead on measures to reduce soil erosion in the river basin which contributes to rapid fluctuations in water levels.
A German transport ministry spokesman said that the government's plans for the Elbe merely aimed to strengthen breakwaters that prevented the river silting up. "We have an international obligation to keep the river open to traffic and these breakwaters have been there for centuries. Some of them have fallen into disrepair," he said.
There are similar concerns about the river Rhine, which is Europe's most frequented commercial inland waterway. In the summer of 2003, a drought reduced water levels in the river to their lowest in four decades and brought river traffic almost to a complete halt.
Environmentalists and Juergen Trittin of the Green party, who was then the Environment Minister, blamed decades of regional and central government development projects on the Rhine. They argued that government planning had led to the deforestation of river banks and the channelling of streams feeding the river into concrete water runs which exhausted the Rhine's natural water supply within days of rainfall.
Germany's water authorities have measured unusually low water levels in the Rhine during the first weeks of 2006, a period when traditionally the river often bursts its banks. However, regional officials say that over the past century the volume of water carried by the Rhine has increased as a result of overall increases in rainfall during the period.
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