Water management and raw-earth construction in protohistory: Uses and transformations of reservoir BS-1625 at the site of Vilars d'Arbeca (Lleida, Spain)

The Fortress of Vilars d'Arbeca (775–300 cal BC) is a reference site for the transition from the Early Iron Age to the Iberian period in the north-east of the Iberian Peninsula. It’s noteworthy, however, that zones to the exterior of these fortified settlements have rarely been the object of thorough analyses as archaeology has normally focused on their interiors. This study presents a series of micromorphological analyses to determine the nature of the infill of Reservoir BS-1625, an elongated structure along the site’s exterior initially identified as a defensive ditch during fieldwork of 2017 (Alonso et al., 2020). This approach allowed defining the processes of formation and function of its infill and how the structure served the fortress. The analyses broke down the infill’s sequence into seven microfacies types, each defined along the lines of its spatial and stratigraphic context. The different findings reveal that BS-1625 served to store rainwater channelled from the interior of the fortification. The evidence clearly demonstrates that the structure thus played a dual role as ditch and reservoir before subsequently serving as a space to produce raw earth for construction. Vilars d'Arbeca is the first site from this timeframe in the north-east of the Iberian Peninsula with a feature of this type. This perspective on the uses and transformation of ditches, reservoirs and spaces along the exterior of the fortified settlement of Vilars d'Arbeca thus sheds new light on aspects of the site’s daily life.