Al Aflaj, Oman
A notable feature of the landscape of Oman is the system of water channels, called aflaj (plural) or falaj (singular), that extends across the country. Basically a water management system, aflaj provide a reliable supply of water to human settlements and for irrigation in the hot, arid conditions of much of the country. They are thought to have originated in pre-Islamic Iran, Persia, and may date back to 1000 BC, and from there, the system spread throughout much of Asia and Africa.
Aflaj consist of a series of well-like vertical shafts, connected by gently sloping tunnels in such a way that large quantities of water are efficiently delivered to the surface without the need for any form of pumping, relying on gravity with the source being at a higher level than their destination. They transport water over long distances in hot dry climates without losing a great deal to evaporation or leakage.
The source of a falaj was normally at the foot of a range of hills or mountains where the water table is close to the surface. Especially near the source but often for long distances the falaj runs in underground channels and can extend for many tens of kilometers. The system has the advantage of being resistant to natural disasters such as earthquakes and floods, and to deliberate destruction in war. Equally important, they are not dependent on rainfall levels, delivering a flow with only small variations from wet to dry years.
In Oman aflaj date back to the Iron Age period and there are still some 3000 still in use today. Many important sites were built on or around a falaj, including Nizwa, Al Hazm and Bait Al Falaj, the Armed Forces Museum. In July 2006, five examples of aflaj were designated as World Heritage Sites by UNESCO.