The Yangtze, the world's third longest river, floods much of China's central and eastern plains each year. Supporters of the dam argue that it can play an instrumental role in downstream flood control, bringing the human and economic toll of the annual floods to a minimum. The stored water can also be released at times of prolonged drought to relieve the parched farms.

But a series of strange weather patterns in 2006 and 2007 prompted many locals to question whether the dam was messing things up instead of helping. Between mid-July to August in 2006, Chongqing was hit with what the weatherman declared as the worst drought in a century. A year later, Chongqing was pelted by the heaviest rainfall in the region in 100 years. Officials said changing climatic conditions, rather than the dam, was to blame. [Nov 2008.]