Hoover Dam, a concrete arch-gravity dam in Black Canyon of the Colorado River. Lake Mead in the background is impounded by the dam.
Glen Canyon Dam
A sideview of the Lake Vyrnwy dam, in Wales, finished in 1888 A dam is a barrier that impoundswater or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees (also known as dikes) are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are often used in conjunction with dams to generate electricity. A dam can also be used to collect water or for storage of water which can be evenly distributed between locations.
The Roman dam at Cornalvo in Spain has been in use for almost two millennia.
Grand Anicut dam on river Kaveri in Tamil Nadu, South India (19th century on 1st-2nd century foundation) The word dam can be traced back to Middle English, and before that, from Middle Dutch, as seen in the names of many old cities. Early dam building took place in Mesopotamia and the Middle East. Dams were used to control the water level, for Mesopotamia's weather affected the Tigris and Euphrates rivers, and could be quite unpredictable.
The earliest known dam is the Jawa Dam in Jordan, 100 kilometres (62 mi) northeast of the capital Amman. This gravity dam featured a 4.5 m (15 ft) high and 1 m (3 ft 3 in) wide stone wall, supported by a 50 m (160 ft) wide earth rampart. The structure is dated to 3000 BC. The Ancient Egyptian Sadd-el-Kafara Dam at Wadi Al-Garawi, located about 25 km (16 mi) south of Cairo, was 102 m (335 ft) long at its base and 87 m (285 ft) wide. The structure was built around 2800 or 2600 B.C. as a diversion dam for flood control, but was destroyed by heavy rain during construction or shortly afterwards. By the mid-late third century BC, an intricate water-management system within...