What is the purpose of a dam?

A dam is a structure built across a river or stream to control the flow of water. Its primary purposes include generating hydroelectric power, providing water for irrigation and drinking, and controlling floods. Dams also create reservoirs, which can be used for recreation, such as boating and fishing. However, they can impact ecosystems by altering natural water flow and displacing wildlife. Examples of famous dams include the Hoover Dam in the United States and the Three Gorges Dam in China, the largest in the world.