the word dam can be traced back to Middle English,[1] and before that, from Middle Dutch, as seen in the names of many old cities. [2] 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 an originally 9 m (30 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. [3][4] 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[5] or 2600 BC. [6] as a diversion dam for flood control, but was destroyed by heavy rain during construction or shortly afterwards. [5][6] During the XIIth dynasty in the 19th century BC, the Pharaohs Senosert III, Amenemhat III and Amenmehat IV dug a canal 16 km long linking the Fayum Depression to the Nile in Middle Egypt.Two dams called Ha-Uar running east-west were built to retain water during the annual flood and then release it to surrounding lands.
The lake called "Mer-wer" or Lake Moeris covered 1700 square kilometers and is known today as Berkat Qaroun. [citation needed] By the mid-late 3rd century BC, an intricate water-management system within Dholavira in modern day India, was built. The system included 16 reservoirs, dams and various channels for collecting water and storing it. [7] Roman dam construction was characterized by "the Romans' ability to plan and organize engineering construction on a grand scale". 8] Roman planners introduced the then novel concept of large reservoir dams which could secure a permanent water supply for urban settlements also over the dry season. [9] Their pioneering use of water-proof hydraulic mortar and particularly Roman concrete allowed for much larger dam structures than previously built,[8] such as the Lake Homs Dam, possibly the largest water barrier to that date,[10] 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. 11] Roman engineers made routine use of ancient standard designs like embankment dams and masonry gravity dams. [12] 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 arch-gravity dams,[13] arch dams,[14] buttress dams[15] and multiple arch buttress dams,[16] 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. [17] Eflatun P? nar 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[18] and is considered one of the oldest water-diversion or water-regulator structures in the world, which is still in use.
[19] The purpose of the dam was to divert the waters of the Kaveri across the fertile Delta region for irrigation via canals. 20] 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 the Prime Minister of Chu (state), Sunshu Ao, flooded a valley in modern-day northern Anhui province that created an enormous irrigation reservoir (100 km (62 mi) in circumference), a reservoir that is still present today. [21] In Iran, bridge dams such as the Band-e Kaisar were used to provide hydropower through water wheels, which often powered water-raising mechanisms.
One of the first was the Roman-built dam bridge in Dezful,[22] which could raise water 50 cubits in height for the water supply to all houses in the town. Also diversion dams were known. [23] Milling dams were introduced which the Muslim engineers called the Pul-i-Bulaiti. 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. [23] Water was conducted from the back of the dam through a large pipe to drive a water wheel and watermill. [24] In the 10th century, Al-Muqaddasi described several dams in Persia.
He reported that one in Ahwaz was more than 910 m (3,000 ft) long,[25] and that and it had many water-wheels raising the water into aqueducts through which it flowed into reservoirs of the city. [26] Another one, the Band-i-Amir dam, provided irrigation for 300 villages. [25] In the Netherlands, a low-lying 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 year old dam, still carries the name Dam Square or simply the Dam. French engineer Benoit Fourneyron developed the first successful water turbine in 1832. The era of large dams was initiated after Hoover Dam was completed on the Colorado River near Las Vegas in 1936.By 1997, there were an estimated 800,000 dams worldwide, some 40,000 of them over 15 m (49 ft) high. [27] Types of dams [edit] Dams can be formed by human agency, natural causes, or even by the intervention of wildlife such as beavers. Man-made dams are typically classified according to their size (height), intended purpose or structure.
By structure [edit] Based on structure and material used, dams are classified as easily created without materials , arch-gravity dams, embankment dams or masonry dams, with several subtypes. Arch dams [edit] Gordon Dam, Tasmania is an arch dam. Main article: Arch damIn the arch dam, stability is obtained by a combination of arch and gravity action. If the upstream face is vertical the entire weight of the dam must be carried to the foundation by gravity, while the distribution of the normal hydrostatic pressure between vertical cantilever and arch action will depend upon the stiffness of the dam in a vertical and horizontal direction. When the upstream face is sloped the distribution is more complicated.
The normal component of the weight of the arch ring may be taken by the arch action, while the normal hydrostatic pressure will be distributed as described above.For this type of dam, firm reliable supports at the abutments (either buttress or canyon side wall) are more important. The most desirable place for an arch dam is a narrow canyon with steep side walls composed of sound rock. [28] The safety of an arch dam is dependent on the strength of the side wall abutments, hence not only should the arch be well seated on the side walls but also the character of the rock should be carefully inspected. Daniel-Johnson Dam, Quebec, is a multiple-arch buttress dam.
Two types of single-arch dams are in use, namely the constant-angle and the constant-radius dam.The constant-radius type employs the same face radius at all elevations of the dam, which means that as the channel grows narrower towards the bottom of the dam the central angle subtended by the face of the dam becomes smaller. Jones Falls Dam, in Canada, is a constant radius dam. In a constant-angle dam, also known as a variable radius dam, this subtended angle is kept a constant and the variation in distance between the abutments at various levels are taken care of by varying the radii.
Constant-radius dams are much less common than constant-angle dams. Parker Dam is a constant-angle arch dam.A similar type is the double-curvature or thin-shell dam. Wildhorse Dam near Mountain City, Nevada in the United States is an example of the type. This method of construction minimizes the amount of concrete necessary for construction but transmits large loads to the foundation and abutments.
The appearance is similar to a single-arch dam but with a distinct vertical curvature to it as well lending it the vague appearance of a concave lens as viewed from downstream. The multiple-arch dam consists of a number of single-arch dams with concrete buttresses as the supporting abutments, as for example the Daniel-Johnson Dam, Quebec, Canada.The multiple-arch dam does not require as many buttresses as the hollow gravity type, but requires good rock foundation because the buttress loads are heavy. Gravity dams [edit] This section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed.
(March 2011) The Grand Coulee Dam is an example of a solid gravity dam. In a gravity dam, the force that holds the dam in place against the push from the water is Earth's gravity pulling down on the mass of the dam. 29] The water presses laterally (downstream) on the dam, tending to overturn the dam by rotating about its toe (a point at the bottom downstream side of the dam). The dam's weight counteracts that force, tending to rotate the dam the other way about its toe.
The designer ensures that the dam is heavy enough that the dam's weight wins that contest. In engineering terms, that is true whenever the resultant of the forces of gravity acting on the dam and water pressure on the dam acts in a line that passes upstream of the toe of the dam.Furthermore, the designer tries to shape the dam so if one were to consider the part of dam above any particular height to be a whole dam itself, that dam also would be held in place by gravity. i. e. there is no tension in the upstream face of the dam holding the top of the dam down.
The designer does this because it is usually more practical to make a dam of material essentially just piled up than to make the material stick together against vertical tension.Note that the shape that prevents tension in the upstream face also eliminates a balancing compression stress in the downstream face, providing additional economy. The designer also ensures that the toe of the dam is sunk deep enough in the earth that it does not slide forward. For this type of dam, it is essential to have an impervious foundation with high bearing strength. When situated on a suitable site, a gravity dam can prove to be a better alternative to other types of dams. When built on a carefully studied foundation, the gravity dam probably represents the best developed example of dam building.
Since the fear of flood is a strong motivator in many regions, gravity dams are being built in some instances where an arch dam would have been more economical. Gravity dams are classified as "solid" or "hollow" and are generally made of either concrete or masonry. This is called "zoning". The core of the dam is zoned depending on the availability of locally available materials, foundation conditions and the material attributes.
The solid form is the more widely used of the two, though the hollow dam is frequently more economical to construct.Gravity dams can also be classified as "overflow" (spillway) and "non-overflow. " Grand Coulee Dam is a solid gravity dam and Itaipu Dam is a hollow gravity dam. Arch-gravity dams [edit] The Hoover Dam is an example of an arch-gravity dam. Main article: Arch-gravity dam A gravity dam can be combined with an arch dam into an arch-gravity dam for areas with massive amounts of water flow but less material available for a purely gravity dam.
The inward compression of the dam by the water reduces the lateral (horizontal) force acting on the dam.Thus, the gravitation force required by the dam is lessened, i. e. the dam does not need to be so massive.
This enables thinner dams and saves resources. Barrages [edit] The Koshi Barrage Main article: Barrage dams A barrage dam is a special kind of dam which consists of a line of large gates that can be opened or closed to control the amount of water passing the dam. The gates are set between flanking piers which are responsible for supporting the water load, and are often used to control and stabilize water flow for irrigation systems.Barrages that are built at the mouth of rivers or lagoons to prevent tidal incursions or utilize the tidal flow for tidal power are known as tidal barrages. [30] Embankment dams [edit] Main article: Embankment dam Embankment dams are made from compacted earth, and have two main types, rock-fill and earth-fill dams. Embankment dams rely on their weight to hold back the force of water, like gravity dams made from concrete.
Rock-fill dams [edit] The Gathright Dam in Virginia is a rock-fill embankment dam.Rock-fill dams are embankments of compacted free-draining granular earth with an impervious zone. The earth utilized often contains a large percentage of large particles hence the term rock-fill. The impervious zone may be on the upstream face and made of masonry, concrete, plastic membrane, steel sheet piles, timber or other material. The impervious zone may also be within the embankment in which case it is referred to as a core.
In the instances where clay is utilized as the impervious material the dam is referred to as a composite dam.To prevent internal erosion of clay into the rock fill due to seepage forces, the core is separated using a filter. Filters are specifically graded soil designed to prevent the migration of fine grain soil particles. When suitable material is at hand, transportation is minimized leading to cost savings during construction. Rock-fill dams are resistant to damage from earthquakes.
However, inadequate quality control during construction can lead to poor compaction and sand in the embankment which can lead to liquefaction of the rock-fill during an earthquake.Liquefaction potential can be reduced by keeping susceptible material from being saturated, and by providing adequate compaction during construction. An example of a rock-fill dam is New Melones Dam in California. Concrete-face rock-fill dams [edit] A concrete-face rock-fill dam (CFRD) is a rock-fill dam with concrete slabs on its upstream face.
This design offers the concrete slab as an impervious wall to prevent leakage and also a structure without concern for uplift pressure. In addition, the CFRD design is flexible for topography, faster to construct and less costly than earth-fill dams.The CFRD originated during the California Gold Rush in the 1860s when miners constructed rock-fill timber-face dams for sluice operations. The timber was later replaced by concrete as the design was applied to irrigation and power schemes. As CFRD designs grew in height during the 1960s, the fill was compacted and the slab's horizontal and vertical joints were replaced with improved vertical joints. In the last few decades, the design has become popular.
[31] Currently, the tallest CFRD in the world is the 233 m (764 ft) tall Shuibuya Dam in China which was completed in 2008. 32] Earth-fill dams [edit] Earth-fill dams, also called earthen dams, rolled-earth dams or simply earth dams, are constructed as a simple embankment of well compacted earth. A homogeneous rolled-earth dam is entirely constructed of one type of material but may contain a drain layer to collect seep water. A zoned-earth dam has distinct parts or zones of dissimilar material, typically a locally plentiful shell with a watertight clay core. Modern zoned-earth embankments employ filter and
