THE THREE GORGES DAM DRAMATICALLY REDUCED THE AMOUNT OF SEDIMENT TRANSPORTED BY THE YANGTZE RIVER IN CHINA AFTER ITS COMPLETION IN 2003. THE TOP IMAGE SHOWS THE DAM SITE DURING CONSTRUCTION IN 1999, WHEN SEDIMENT COLORS THE FREE-FLOWING RIVER BROWN. THE BOTTOM IMAGE SHOWS THE COMPLETED DAM IN 2010. DARK BLUE WATER FLOWS THROUGH THE DAM WITHOUT SEDIMENT, WHICH IS TRAPPED UPSTREAM IN THE RESERVOIR, ONE OF AN ESTIMATED 50,000 IN THE RIVER BASIN