Jawa Dam
Encyclopedia
The Jawa Dam is the remains of an ancient masonry
gravity dam on Wadi Rajil at Jawa in Mafraq Governorate
, Jordan
, 58 kilometres (36 mi) north of Azraq. It is the oldest known dam in the world, dating back to 3000 BC. The dam was part of a water supply
system that eventually consisted of other smaller dams to support the growing local town of Jawa. Therefore, the term Jawa Dams is sometimes used to describe the dams around Jawa. The Jawa Dam, though, is the largest of the dams and withheld the largest reservoir
.
Svend Helms, who directed an excavation of the area in 1970, determined that the Jawa Dam was used to harvest rainwater. After winter precipitation runoff was diverted from Wadi Rajil, it was transferred through a small canal to a depression in the ground that was sealed off with a rock wall. This rock wall was the Jawa Dam; it had a 2 metres (6.6 ft) thick core of tampered clay
, ash
and soil
. The core was surrounded with basalt
stone walls. Loam
and soil were placed at the downstream side of the dam to strengthen it and an impervious blanket was placed on the upstream heel to prevent leaks. On top of this blanket, pervious rock-fill was placed to help release water and drain the reservoir. The dam was later heightened by 1 – and its core expanded at the same time to 7 metres (23 ft) thick to further strengthen it.
Over time, other dam
s, weir
s and small canal
s were built in Jawa to expand the system and increase the water supply. Weirs eventually diverted water into a system of ten reservoirs for farming, herding and human consumption. The Jawa Dam's reservoir held half of the system's combined water storage capacity. The town of Jawa was estimated to quickly reach a size of 2,000 before it collapsed.
Masonry
Masonry is the building of structures from individual units laid in and bound together by mortar; the term masonry can also refer to the units themselves. The common materials of masonry construction are brick, stone, marble, granite, travertine, limestone; concrete block, glass block, stucco, and...
gravity dam on Wadi Rajil at Jawa in Mafraq Governorate
Mafraq Governorate
Mafraq is one of the governorates of Jordan, located to the north-east of Amman, capital of Jordan. It has a population of 254,219 with a percentage of 4.5% of Jordan's population...
, Jordan
Jordan
Jordan , officially the Hashemite Kingdom of Jordan , Al-Mamlaka al-Urduniyya al-Hashemiyya) is a kingdom on the East Bank of the River Jordan. The country borders Saudi Arabia to the east and south-east, Iraq to the north-east, Syria to the north and the West Bank and Israel to the west, sharing...
, 58 kilometres (36 mi) north of Azraq. It is the oldest known dam in the world, dating back to 3000 BC. The dam was part of a water supply
Water supply
Water supply is the provision of water by public utilities, commercial organisations, community endeavours or by individuals, usually via a system of pumps and pipes...
system that eventually consisted of other smaller dams to support the growing local town of Jawa. Therefore, the term Jawa Dams is sometimes used to describe the dams around Jawa. The Jawa Dam, though, is the largest of the dams and withheld the largest reservoir
Reservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...
.
Svend Helms, who directed an excavation of the area in 1970, determined that the Jawa Dam was used to harvest rainwater. After winter precipitation runoff was diverted from Wadi Rajil, it was transferred through a small canal to a depression in the ground that was sealed off with a rock wall. This rock wall was the Jawa Dam; it had a 2 metres (6.6 ft) thick core of tampered clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
, ash
Wood ash
Wood ash is the residue powder left after the combustion of wood. Main producers of wood ash are wood industries and power plants.-Composition:...
and soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
. The core was surrounded with basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
stone walls. Loam
Loam
Loam is soil composed of sand, silt, and clay in relatively even concentration . Loam soils generally contain more nutrients and humus than sandy soils, have better infiltration and drainage than silty soils, and are easier to till than clay soils...
and soil were placed at the downstream side of the dam to strengthen it and an impervious blanket was placed on the upstream heel to prevent leaks. On top of this blanket, pervious rock-fill was placed to help release water and drain the reservoir. The dam was later heightened by 1 – and its core expanded at the same time to 7 metres (23 ft) thick to further strengthen it.
Over time, other dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...
s, weir
Weir
A weir is a small overflow dam used to alter the flow characteristics of a river or stream. In most cases weirs take the form of a barrier across the river that causes water to pool behind the structure , but allows water to flow over the top...
s and small canal
Canal
Canals are man-made channels for water. There are two types of canal:#Waterways: navigable transportation canals used for carrying ships and boats shipping goods and conveying people, further subdivided into two kinds:...
s were built in Jawa to expand the system and increase the water supply. Weirs eventually diverted water into a system of ten reservoirs for farming, herding and human consumption. The Jawa Dam's reservoir held half of the system's combined water storage capacity. The town of Jawa was estimated to quickly reach a size of 2,000 before it collapsed.