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A dam is a barrier that impounds water or underground streams. Reservoirs created by dams not only
suppress floods but also provide water for such activities as irrigation, human consumption, industrial
use, aquaculture, and navigability. Hydropower is 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. 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.
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.
Ancient dams[edit]
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.
The earliest known dam is the Jawa Dam in Jordan, 100 kilometres (62 mi) northeast of the capital
Amman. This gravity dam featured an originally 9metrehigh (30 ft) and 1 mwide (3.3 ft) stone wall,
supported by a 50 mwide (160 ft) earth rampart. The structure is dated to 3000 BC.
A sideview of the Lake Vyrnwy dam, in Wales, finished in 1888
Karapuzha Dam, an earth dam in the Indian state of Kerala
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The Ancient Egyptian SaddelKafara Dam at Wadi AlGarawi, 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 BC as a diversion dam for flood control, but was destroyed by heavy rain during construction
or shortly afterwards. During the XIIth dynasty in the 19th century BC, the Pharaohs Senosert III,
Amenemhat III and Amenmehat IV dug a canal 16 km (9.9 mi) long linking the Fayum Depression to the
Nile in Middle Egypt. Two dams called HaUar running eastwest were built to retain water during the
annual flood and then release it to surrounding lands. The lake called "Merwer" or Lake Moeris covered
1,700 km (660 sq mi) and is known today as Berkat Qaroun.
One of the engineering wonders of the ancient world was the Great Dam of Marib in Yemen. Initiated
somewhere between 1750 and 1700 BC, it was made of packed earth triangular in cross section,
580 m (1,900 ft) in length and originally 4 m (13 ft) high running between two groups of rocks on either
side, to which it was linked by substantial stonework. Repairs were carried out during various periods,
most important around 750 BC, and 250 years later the dam height was increased to 7 m (23 ft). After
the end of the Kingdom of Saba, the dam fell under the control of the Ḥimyarites (~115 BC) who
undertook further improvements, creating a structure 14 m (46 ft) high, with five spillway channels, two
masonryreinforced sluices, a settling pond, and a 1,000 m (3,300 ft) canal to a distribution tank. These
extensive works were not actually finalized until 325 AD and allowed the irrigation of 25,000 acres
(100 km ).
By the midlate 3rd century BC, an intricate watermanagement system within Dholavira in modernday
India was built. The system included 16 reservoirs, dams and various channels for collecting water and
storing it.
Eflatun Pınar is a Hittite dam and spring temple near Konya, Turkey. It is thought to be from the time of
the Hittite empire between the 15th and 13th century BC.
The Kallanai is constructed of unhewn stone, over 300 m (980 ft) long, 4.5 m (15 ft) high and 20 m
(66 ft) wide, across the main stream of the Kaveri river in Tamil Nadu, South India. The basic structure
dates to the 2nd century AD and is considered one of the oldest waterdiversion or waterregulator
structures in the world which is still in use. The purpose of the dam was to divert the waters of the
Kaveri across the fertile delta region for irrigation via canals.
Du Jiang Yan is the oldest surviving irrigation system in China that included a dam that directed
waterflow. It was finished in 251 BC. A large earthen dam, made by Sunshu Ao, the prime minister of
Chu (state), flooded a valley in modernday northern Anhui province that created an enormous irrigation
reservoir (100 km (62 mi) in circumference), a reservoir that is still present today
Roman engineering
Roman dam construction was characterized by "the Romans' ability to plan and organize engineering
construction on a grand scale." Roman planners introduced the thennovel concept of large reservoir
dams which could secure a permanent water supply for urban settlements over the dry season. Their
pioneering use of waterproof hydraulic mortar and particularly Roman concrete allowed for much larger
dam structures than previously built, such as the Lake Homs Dam, possibly the largest water barrier
to that date, and the Harbaqa Dam, both in Roman Syria. The highest Roman dam was the Subiaco
Dam near Rome; its record height of 50 m (160 ft) remained unsurpassed until its accidental destruction
in 1305.
Roman engineers made routine use of ancient standard designs like embankment dams and masonry
gravity dams. Apart from that, they displayed a high degree of inventiveness, introducing most of the
other basic dam designs which had been unknown until then. These include archgravity dams, arch
dams, buttress dams and multiple arch buttress dams, all of which were known and employed
by the 2nd century AD (see List of Roman dams). Roman workforces also were the first to build dam
bridges, such as the Bridge of Valerian in Iran
In Iran, bridge dams such as the Bande Kaisar were used to provide hydropower through water wheels,
which often powered waterraising mechanisms. One of the first was the Romanbuilt dam bridge in
Dezful, which could raise water 50 cubits in height for the water supply to all houses in the town. Also
diversion dams were known. Milling dams were introduced which the Muslim engineers called the PuliBulaiti.
The first was built at Shustar on the River Karun, Iran, and many of these were later built in
other parts of the Islamic world. Water was conducted from the back of the dam through a large pipe
The Roman dam at Cornalvo in Spain has been in use for almost two millennia.
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Remains of the Bande Kaisar dam, built by the Romans in the 3rd century AD
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to drive a water wheel and watermill. In the 10th century, AlMuqaddasi described several dams in
Persia. He reported that one in Ahwaz was more than 910 m (3,000 ft) long, and that it had many
waterwheels raising the water into aqueducts through which it flowed into reservoirs of the city.
Another one, the BandiAmir dam, provided irrigation for 300 villages.
Middle Ages[edit]
In the Netherlands, a lowlying country, dams were often applied to block rivers in order to regulate the
water level and to prevent the sea from entering the marsh lands. Such dams often marked the
beginning of a town or city because it was easy to cross the river at such a place, and often gave rise to
the respective place's names in Dutch.
For instance the Dutch capital Amsterdam (old name Amstelredam) started with a dam through the river
Amstel in the late 12th century, and Rotterdam started with a dam through the river Rotte, a minor
tributary of the Nieuwe Maas. The central square of Amsterdam, covering the original place of the 800
yearold dam, still carries the name Dam Square or simply the Dam.