Report says dams destroy rivers

The State of the World’s Rivers, an interactive survey of the world’s 50 largest river basins, found almost 6,000 dams (a fraction of the estimated 50,000 that exist in all rivers on earth). The Hai Ho, Tigris-Euphrates and Wisla basins were found to have the highest degree of fragmentation.
The study found correlations between fragmentation by dams and poor water quality, mercury concentrations, sedimentation, thermal pollution and declining biodiversity.
The data was collated by International Rivers (IR). Executive director of IR Jason Rainey said the global perspective showed that rivers worldwide needed greater attention and protection.
“The evidence we’ve compiled of planetary-scale impacts from river change is strong enough to warrant a major international focus on understanding the thresholds for ‘river change’ in the world’s major basins, and for the planet as a whole system.”
But IR warns that the correlations with poor health are only statistical and further study of individual cases is necessary to understand exactly how dams impact rivers.
Across the world thousands more dams are being planned. In Brazil’s Paraná and Amazon basins there are 666 dams in production. China plans to build 94 large and 73 small dams on the relatively healthy Yangtze. Ethiopia is also building a major dam on the River Nile. Egypt and Sudan currently get the lion’s share of the Nile’s waters under colonial-era treaties. While Sudan backs Ethiopia’s plans, Egypt has remained opposed to the dam’s construction.