Low-cost seismic geophysical methods for the detection of karez: A case study on the Erbil Plain (Kurdistan Region of Iraq)

Underground gravity-flow channels ( karez ; also qanat ) have been an important technology for accessing subterranean water resources and supplying the water needs of (esp. agricultural) communities throughout the Middle East and North Africa and elsewhere for many centuries, but in the past several decades have suffered the effects of groundwater mining and mechanized agriculture. Study and conservation of these hydraulic systems typically depends on the persistence of surface traces of the buried components (e.g., preserved maintenance shaft openings). These traces are easily erased by intensive agriculture, so that many of the regions where karez have been important but which are heavily cultivated today have a major barrier to detection, biasing archaeological research to karez landscapes under a narrow range of taphonomic conditions and limiting prospects for the revitalization of these hydraulic systems by local communities. We demonstrate here a user-friendly technique for geophysical survey using smartphone accelerometers to sense surface-wave energy from an active seismic source, enabling the efficient and low-cost detection of relatively deeply-buried (∼20 m) karez systems without surface traces. We discuss the application of this technique particularly to the rapid characterization and study of karez landscapes on the Erbil Plain in the Kurdistan Region of Iraq.