The Traditional Aflaj Irrigation System

THE PHYSICAL STRUCTURE OF THE FALAJ

The falaj basically consists of a tunnel to tap the ground water and bring it to the surface for distribution to crops and housing without mechanical use. Excavating was carried out using man power and very primitive materials, nevertheless, it has been running for centuries with high efficiency of water delivery. Water flow depends on gravity gradient along the tunnel starting from the mother well and for tens of kilometers long.
At the end of the tunnel water is divided into lateral tunnels and then to small channels for individual gardens. Mostly, water is led to only one garden at a time. The yield of aflaj varies according to ground-water characteristics, the porosity of the soil, and the season. Parks and Smith reported that the physical principle of this method of gravity water varies according to hydrological and topographic conditions. The two major classes of qanats sited in extensive alluvial deposits such as Iran, and aflaj in restricted wadi gravels typical of Oman.
When a new falaj is to be dug, a knowledgeable man of water availability signs is asked to find a place with abundance of underground water, normally, on the upper slope of an alluvial fan. Digging of the mother well where the water has been found starts first followed by other shafts until the farm lands are reached. Since the Persian introduced falaj to Oman, most of aflaj's layout remain the same.

The mother well (umm Al falaj):
The location of the mother well, which is the main source of falaj, is normally downstream. Here the volume of water in storage is considerable but does not lie too deep, the water quality is also high . Advantage of building the mother well downstream is; reduce labor and establishment cost, minimize the losses of water through evaporation and peculation, and reduce salt accumulation.

Access shafts:
The access shafts are built along the tunnel to provide ventilation and for removal of debris. The shafts are located every 20 meters, and they vary in their depth according to the depth of the underground tunnel. At the shaft mouth a ring of burned clay is built to prevent flooding water from entering the tunnel and destroy the falaj if the tunnel collapse. In many cases, these rings are covered to prevent animal and people from falling into it, as well as protection of water from pollutants.

The tunnel:
Having located a suitable water supply, the tunnel isthen dug back to the mother well at a gradient of 1/500 to 1/2,500 to prevent erosion and siltation. The size of the tunnel is just enough for the worker to crawl through, while the length varies according to the nature of terrain. A technique that is used for crossing wadi beds is either inverted siphon or bridges.

The layout of the falaj varies considerably depending on the place and the type of falaj. At the very top of the falaj, where the falaj qanat is open, the drinking water may be drawn, called sharia. This is the first permitted use of water and the access is free for all. In case of large aflaj, the channel is splited into two channels . After drinking facilities, bathing places are built for men and then for women and children. Then the channel passes through the forts and mosques until it reaches the mughisla for washing the dead. The falaj is considered public property and no individual has a particular right in it. Drawing of water for domestic use and watering of animals is free for all. The falaj is then reaches the garden where a special distribution system was developed to distribute the irrigation water.

The system of water shareholding and the ways falaj water is distributed are complex. The basic of water distribution is the dawran, cycle by which the falaj is distributed around the irrigated land. Aflaj rotate on a certain period, each piece of land or a farm is allocated a period of time. Part of the water is permanently owned by the falaj founders depending on their share of money or labor and it is inherited and rarely change hands, this is called Mulk. The other part is rented to those who have no share in the falaj or for farms which need extra water than the allocated fair. Primarily, the water distribution is based on either time or volume, depending on the size of the falaj, however, the time based type is more common.
According to Al-Murshudy, the unite of time is as follows:
Ba'ada 12 hours 24 athar Rabiya 3 hours 6 athar Athar 1/2 hour 1 athar Qama 7 1/2 minutes 1/4 athar These units are based on a shadow's length. Water time was measured by the increase in the length of a man's shadow, and at night by the movement of the stars. This cycle may vary from village to another or according to the size of the falaj and the soil characteristics. Where the cycle in one place is four hours, it is infrequently as long as 16 days in another. The settlements of finest soils generally have longer cycles. The basic principle is that the individual shareholder's water is delivered to him at an appointed place and time by means of network of distributory channels that belong to the falaj itself.
The falaj-own water is available for rental (by auction) and the income is used for falaj repairs and maintenance. Other falaj fund come from falaj properties such as the date palm or trees along the channel. This system of water distribution is accepted by all and maintained the same until nowadays. This helped the aflaj survival by its close ties to the community, and its management by those most familiar with it and most affected by its state of health.

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