Dam problems - Dams examples

A Silent Flood - an unexpected threat in Argentina

The Iberá marshes lie in the centre and north-east of the province of Corrientes, Argentina. The system of marshes, lagoons and swamps cover an area which, depending on the time of year, ranges from 7,800 to 13,000 square kilometres.

The marshes have been isolated and undisturbed for centuries and are particularly well-known for their unique 'embalsados'; massive carpets of floating vegetation in the bodies of open water.

These true floating islands, complete with fully-grown trees, are made up of dead or decomposing organic material and are found nowhere else in the world. The marshes are also home to over eighty different fish, dozens of different species of mammals, reptiles and amphibians and nearly three hundred species of birds.

But the Iberá marshes are under threat - from too much water! The Yacyretá dam on the nearby Paraná river was completed in 1993 to control flooding and to provide power and water for irrigation. Now there is strong evidence that water from the huge Yacyretá lake behind the dam only a few hundred meters from the marshes, is seeping into the lower lying marshes, threatening to drown them and turn the area into a shallow lake.

In 1995, two years after the dam was filled, farmers around the marsh reported widespread flooding of their fields and trees started dying due to the rising water table. Studies by the National University of the Centre of Buenos Aires Province, supported by the European Commission, could find no reason for this other than the movement of water from the Yacyretá lake into the marshes.

This alarming situation could be made considerably worse very quickly by the announcement by the operators of the Yacyretá dam to increase the water-level of the lake behind the dam to 83m from its current level of 76m.

WWF's partner in Argentina, FVSA, is one of the environmental organisations that are calling for an independent and objective study of the impact of the seepage of water from the Yacyretá dam into the Iberá marshes. Only in this way will the true magnitude of the problem be understood. WWF and the other organisations also demand that, until the study is completed, the water level in the dam must not be raised.