VOLTA GRANDE, Brazil - The Xingu River, the largest tributary of the Amazon, runs wide and swift this time of year. Its turquoise waters are home to some 600 species of fish, including several not found anywhere else on the planet. A thick emerald canopy of trees hugs its banks, except in places where man has carved out pastures for cattle.
Now man, in the form of the Brazilian state power company, wants to harness a section of the Xingu by building the world's third-biggest dam.
