From: Wildlife Conservation Society
Published August 24, 2017 02:12 PM

Potential Impacts of Planned Andean Dams Outweigh Benefits, Scientists Say

An international team of scientists investigating the effects of six planned or potential Andean dams on the Amazon river system has found that major negative ecological impacts can be expected both above the dams and throughout the lowland floodplains and the Amazon Delta, according to WCS (Wildlife Conservation Society), the Instituto Nacional de Pesquisas da Amazonia, and other groups.
 
The authors of the study warn that, if not well planned, the construction of these dams and other infrastructure development in the Andes headwaters could have catastrophic effects across the entire Amazon River basin and threaten the food security of millions of people.
 
The study titled “The potential impact of new Andean dams on the Amazon fluvial ecosystem,” was recently published in PLOS ONE.
 
The study’s models found that the most dramatic effect expected was an estimated reduction of 894 million tons per year in sediments flowing downstream of the six dams (Perú: Pongo de Manseriche, Inambari, TAM 40, Pongo de Aguirre; Bolivia: Angosto del Bala and Rositas). This reduction represents 69 percent of all sediments flowing out the Andes and 64 percent  of the entire Amazon  sediment supply and is expected to extend to the Amazon river main channel, impacting the entire central floodplain and delta region.
 
The Andes Mountains occupy only 11 percent of the Amazon basin, but supply 93 percent of the sediments and most of the nutrients carried by the Amazon river system. Sediment dynamics play an important role in shaping the Amazon’s fluvial landscape, moving and depositing sand, rocks, soil, and nutrients from the Andes to the rest of the Amazon basin.
 
“The expected reduction of sediment and nutrients beyond the dam sites would be catastrophic for the region’s wildlife as well as countless communities that rely on the river for their agricultural needs,” said Bruce Forsberg, scientist for Instituto Nacional de Pesquisas da Amazonia and lead author of the study.
 
Since the Andes is the principal source of sediments to the Amazon river system, the consequences of this massive reduction will be dramatic: river channels will become deeper, reducing seasonal floods which are necessary to bring fluvial sediments and nutrients to floodplain environments and provide connectivity between environments for both migrant fish and people.

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