Exploration, mapping and characterization of filtration galleries of the Pica Oasis, northern Chile: A contribution to the knowledge of the Pica aquifer

In arid areas, the efficient management of scarce water resources is key for population survival and development. One of the oldest and greatest ancient water management system in drylands is the filtration gallery. Originated from ancient Persia, they were spread to other regions and cultures, and are found in the oasis of Pica, in the Atacama Desert. A filtration gallery consists of an almost horizontal tunnel dug underground until it reaches a water-bearing zone. It allows to tap and drains out groundwater, and thus a direct contact with groundwater table. With the objective to understand groundwater processes, preserve the water and geoheritage of one of the driest places on Earth and improve land-use planning, the present work explored and studied the filtration galleries, locally called socavones, of the oasis of Pica. Through direct exploration, topographical survey and geo-electrical prospection, 24 socavones were identified, mapped and their main physical features described, showing common traits with filtration galleries described worldwide, but also proper features highlighting their originality. The findings of the geological and hydrogeological studies of the socavones, complemented by physical and chemical analysis, allow to identify new groundwater recharge processes and, thus, to review and complete the hydrogeological model of the local aquifer of Pica. Most socavones are abandoned today, owing to physical and socioeconomic changes. Nevertheless, this study concludes that they can still have a role to play in the groundwater management of this arid area.