Hydrology and The Ancient Sites
Following a long-lived hyper-arid phase, the onset of modern climatic conditions allowed oasis settlements to make their first appearance in the Hajar region sometime in the second half of the 4th millenium B.C. Without any permanent surface flow in the area, groundwater provides the most reliable water supply and ancient settlements tend to be located where, due to hardrock constriction, storage capacity is greater and potable water can be easily extracted.
In the Wadi Bahla, the two most suitable localities are those of Bahla and Bisya but, while both exhibit ancient remains, Bisya, the more favoured, impressively displays the physical traces of a series of oasis settlements.
The Bisya Area Site, which is 100 sq km and expanding, occupies the southern part of the wadi plain between the Wadi Bahla and its major tributary, the Wadi Sefam, and virtually surrounds the town of Bisya which is situated just above the place where the two wadis meet, and where the Wadi Bahla changes its name to the Wadi Amayri. The site demonstrates a history of settlement shift from northeast to southwest which has been influenced by the alignment of the groundwater pathways that trend away from the Wadi Bahla, salinisation of the soil, irrigation problems and human social and political behaviour.
The al-Ghubrat Bahla Site occupies agricultural land that stretches northwards from the walled town of Bahla, between the eastern bank of the Wadi Bahla and the Jabal named Horat Kid. Because its soils display a sufficient contrast in magnetic susceptibility for features such as ditches to be detectable by geophysical survey, it has revealed a complex network of falaj channels and features that hint at the important role of the falaj within the community.