Watering the desert: Oasis hydroarchaeology, geochronology and functionality in Northern Arabia

The phenomenon of very extended desert oases settlements, mega-sites featuring complex irrigation systems and monumental walls has long been observed in Northern Arabia. In the past, it has been linked to the settling down of nomadic components of the population and dated through archaeological material to the Late Bronze or Iron Ages (late second to mid-first millennium BCE). Since 2014 we have been investigating this development through the case study of the oasis of Qurayyah, a walled site of over 300 ha (Tabuk, NW Saudi Arabia). After mapping the geomorphological and hydroarchaeological layout of this ancient settlement, we established the age of key locations of the site through OSL and radiometric measurements from controlled stratigraphic excavations. We could thus confirm that a major – the largest so far documented in Arabia – flood protection and surface water harvesting system (SWHS) was developed already during the Early Bronze Age (2900–2600 calBCE) onto the relict late Pleistocene playa landscape. This sophisticated anthropogenic hydraulic infrastructure enabled the foundation of the river oasis and construction of the permanent walled settlement. Since different components of the SWHS erected on the site (dam, inlet, canals, weirs, outlet, etc.) resulted being synchronic, they are understood as functional elements of one and the same system. A test of the functionality of the identified SWHS for different rainfall scenarios has confirmed that the volume of its catchment’s surface-water supply was sufficient for irrigation, productive and drinking needs of the large oasis since its Early Bronze Age creation.