| Jawa Dam | |
|---|---|
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| Location | Jawa, Mafraq Governorate, Jordan |
| Coordinates | |
| Construction began | ~3000 BC |
| Dam and spillways | |
| Type of dam | Gravity, masonry |
| Height | 4.5 m (15 ft) |
| Length | 80 m (260 ft) |
| Base width | 4.5–5 m (15–16 ft) |
| Impounds | Wadi Rajil |
| Reservoir | |
| Creates | Jawa Reservoir |
| Capacity | 31,000 m3 (1,100,000 cu ft) est. |
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.[1][2][3]
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-metre (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.[1][4] The dam was later heightened by 1–2 metres (3.3–6.6 ft) and its core expanded at the same time to 7 metres (23 ft) thick to further strengthen it.[2]
Over time, other dams, weirs and small canals 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.[2]