Vienna  - Although the Danube is getting cleaner, the lack of sewage systems in Central and Eastern Europe continues to strain Europe's second longest river, a new study says.

In the upper stretch of the Danube in Germany and Austria, wildlife is disappearing because of river regulation, the International Commission for the Protection of the Danube River (ICPDR) said in its survey which it presented in Vienna on Thursday.

The study shows that the river is less polluted by chemicals than it was during an earlier study in 2001.

"In general, we have a good situation," said Philip Weller, executive secretary of the ICPDR.

However, pollution from human waste remains a problem, especially near bigger cities like Budapest, Belgrade and Bucharest. The ICPDR called on these cities to quickly build waste water treatment plants.

The highest levels of E coli bacteria, which are a sign of human waste, were found in the stretch of river between Budapest and Belgrade, the study said.

Agriculture in Central and Eastern Europe is another area of concern. Although agriculture has decreased after the collapse of communist systems in the late 1980s, the ICPDR is concerned that fertilizers could become a problem as the farming sector grows.

"Rising productivity has to happen without more pesticides and nutrients entering the river," Weller said.

In Germany and Austria, electric power plants along the river and regulation of the waterway strain the ecosystem, the study found.

In these two countries, only three areas are still in near-natural condition, namely an area between Regensburg and Passau in Bavaria, the Wachau region west of Vienna, and the floodplain forest downstream from Vienna.

In the regulated parts of the Danube, the number of fish, insect and plant species are decreasing, the ICPDR's scientists said.

The head of the Danube survey, Igor Liska, said it was "surprising" that 40 per cent of sites monitored along the river were in a good or adequate status. But he noted that for the rest of the Danube, "this doesn't mean the situation is beautiful."

The Danube survey was conducted during six weeks in 2007. Three ships were used to study 96 sites along the river, which spans ten countries and runs for around 2,900 kilometres from the Black Forest in Germany until it reaches the Black Sea in Romania and the Ukraine. (dpa)