A boy crosses the muddy bottom of a normally deep part of the Rio Negro, a tributary to the Amazon river, in the city of Manaus, Oct 21, 2010. [Photo/Agencies]

A skiff navigates along the only stream left in the middle of a normally deep part of the Rio Negro, a tributary to the Amazon river, in the city of Manaus, Oct 21, 2010. [Photo/Agencies]