Ground Penetrating Radar Surveys to Detect Ancient Aflaj in the Hajar Region of Oman

Ground penetrating radar (GPR) is a standard tool in archaeological surveying, and offers high-resolution imaging of buried archaeological targets. In this paper, we explore the potential of GPR methods to detect ancient irrigation channels, aflaj (singular: falaj), in Oman’s Hajar Region. These aflaj, dating from the second-half of the 4th millennium BC, are associated with ancient settlements called Hajar Oasis Towns, and provide the most reliable means of water supply in the region. Locating the aflaj with geophysical methods can be difficult since they typically lack a geophysical contrast with their host material. They occasionally have anomalous magnetic properties, allowing them to be detected with magnetometry and thereafter excavated. However, where a magnetic contrast is absent, we trial the application of GPR. During two field seasons, we acquired GPR data (using a 500 MHz Sensors&Software system) around three Hajar Oasis Towns close to the modern towns of Bahla and Bisya, in Oman. For the most part, we acquired pseudo-3D GPR grids sampled at 5x50 cm resolution. As with magnetomtery, it appears that aflaj are only occasionally detectable with GPR. In one survey grid, a falaj is detectable and is shown to extend further north from the current limit of its excavation; however, no aflaj are confirmed elsewhere, and they cannot be detected even when acquired over known falaj positions. Nonetheless, our surveys have revealed new archaeological features of the Hajar Oasis Towns, including buried pits from which ancient pottery fragments were recovered. We suggest that the material filling the ancient aflaj generally lacks sufficient physical contrast with either its overburden or host-rock to be reliably imaged with GPR, but that GPR has other interesting applications in the Hajar Region.