A dam is a physical barrier constructed across a river or waterway to control the flow of or raise the level of water.
The purpose of a dam may be for flood control, irrigation needs, hydroelectric power production, and/or recreation usage.
The Three Gorges Dam along the Yangtze River in China, which is slated to open in 2008, will be the largest river dam in the world. This dam is controversial, as there are environmental, human rights, and property rights issues associated with the construction of this dam. [1]