Usefulness of surface water retention reservoirs inspired by 'Permaculture Design': A case study in southern Spain using bucket modelling

Water harvesting (WH) techniques have experienced a renaissance within a grassroots sustainability concept and movement called 'permaculture'. Over the past decade, there has been a growing interest in the uptake of permaculture inspired solutions designed to restore the water cycle at a landscape level and to facilitate the delivery of ecosystem services as part of a holistic farming approach. In this study, we assessed four reservoirs built on a fruit farm in southern Spain in terms of usefulness. A simple hydrological model was developed utilising on-site data and two free calibration parameters, infiltration and evapotranspiration. The model matches the observations on the ground well, but indicates limited potential of WH within the boundaries of this particular farm. As the decade preceding the reservoir's inception received more rain (2000-2010), this may have led to a misjudgement for on-farm water harvesting potential in the planning phase. We conclude that the design of WH reservoirs or water landscapes as a contribution to reversing desertification processes and mitigating climate change would benefit from long-term studies on the ground. Moreover, modelling-based scenario analyses can help better understand the dynamics and extent of its potential in establishing an effective and economically viable land restoration process for the region, taking into account climate change projections of increasing desertification in the Mediterranean basin, thereby contributing to the water-soil-food nexus, addressing sustainable development goals (SDGs) related to food (2), water (6), responsible consumption and production (12), climate action (13) and life on land (15).