Oasis Irrigation: The Aflaj
In the absence of perennial surface flow anywhere in northern Oman, the inhabitants of the interior have traditionally depended on a complex aquifer of groundwater pathways which, in turn, are dependent on recharge from infrequent rain and flooding. To access this source, they have employed falaj (pl. aflaj) irrigation technology whereby a system of sub-surface to surface channels conveys groundwater by means of gravity from a mother-well (umm) – for a distance of many kilometres – to the settlements and date plantations it serves. This is the phenomenon that not only shapes the oasis landscape but also forms a part of it and the type of settlement it creates is a discrete, demarcated unit, organised around a cultivated territory, in which the date-palm is the primary perennial crop.
Without aflaj, the ancient agricultural settlements of the interior would never have survived. These narrow ribbons of water were the "lifeblood" that sustained the ancient oases and they also played an important role in the community: providing water for a variety of uses, influencing laws affecting both land and society, and inspiring the management of time by means of the sun and stars.
Our discovery and ongoing investigation of a 5000 year old 14C dated falaj (Falaj A) in a Hajar Oasis Town at the site of al-Ghubrat Bahla, followed by the discovery of con- temporary aflaj (Falaj 1 and its tributary, Falaj 2) in the earlier of the two Hajar Oasis Towns at the Bisya Area Site, not only points to Arabia - and not Iran, as formerly thought - as the homeland of falaj irrigation but also testifies to its antiquity. The discovery has also opened the way to exploring the internal landscape of the Hajar Oasis Towns, the key role the falaj would have played in the community, and early falaj technology.
In order to locate and track the aflaj, we have employed geophysical survey, excavation, manual tracing and even dowsing. We have learned that each falaj system creates a complex network of primary channels, tributaries and bifurcation that snake across the landscape and link the major demarcating monuments of the Hajar Oasis Towns. The channels we have uncovered to date are partly open-sky conduits, strengthened by cross-braces and spanned by occasional bridges, and partly lengthy tunnels that sometimes travel beneath buildings. They are never more than 40-60 cms wide in order to confine the water laterally and reduce salinity. Variations in depth at the Bisya Area Site suggest hydraulic complexity.
As each primary channel proceeds upstream towards its mother-well (umm), it will become an ever more deeply buried tunnel excavated out of rock and cemented conglomerates. We shall therefore be employing Ground Penetrating Radar to trace the aflaj to their source, to explore the lengthy downstream tunnels and other features, and to provide continuous profiles of the main arteries, their feeder channels and off-take branches.