By capturing and storing water, then releasing it as needed, dams enable the production of hydroelectric power, provide a controllable water source for homes, businesses and irrigation, create recreation areas and help control flooding. According to the United States Geological Survey, the electricity generated from hydroelectric plants powered by dammed rivers provided 95 percent of the U.S. energy production in 1995. Dams are also used to stabilize water flow, reclaim land and restore water levels to inland seas and lakes.
In the southwest U.S., the dams along the Colorado River supply power to more than 5 million people across several states. The best-known of the Colorado River dams is the Hoover Dam, which was built between 1931 and 1936 during the height of the Great Depression. It was the largest concrete dam construction project attempted at that time.
The ancient Romans pioneered the art of early dam construction. They were the first to understand the benefits of impounding large amounts of water to ensure the availability of a water supply for their settlements during the dry seasons. Early Roman engineers relied upon inventive design concepts and waterproof materials to construct dams that were larger than anything previously built.
The 19th century Industrial Revolution introduced new building materials and engineering skills that enabled the construction of dams that surpassed the size of previous efforts. The era of large dams was launched by the completion of the Aswan Low Dam on the Nile River in 1902 by John Aird & Co., a leading British engineering firm.