The first annual report on the health of the Yangtze River concluded that human activity has left large parts of it in a "critical condition", AFP reported, citing state media. More than 600 kilometers of the 6,200km river are in trouble as a result of pollution, excessive damming and too much surface traffic. The report also found that 30% of the Yangtze's tributaries are seriously polluted and called for a management system to be put in place to prevent the situation worsening. "The impact of human activities on the Yangtze water ecology is largely irreversible," said Yang Guishan, a researcher with the Nanjing Institute of Geography and Limnology and one of the chief editors of the report. A separate study found that cities along the river discharged at least 14.2 billion tons of polluted water every year, 42% of the national total. The Yangtze accounts for about 35% of China's total fresh water resources.