A Novel, Ecology-Inclusive, Hybrid Framework for Rainwater Harvesting Site Selection in Arid and Semi-Arid Regions

The water crisis is a critical issue, particularly in arid and semi-arid regions where rainfall is limited. Rainwater harvesting systems have been introduced in many locations to capture what rainfall does occur, but selection of the optimum site is vital to ensure efficient capture and storage. Over the past few decades, a range of frameworks for ranking proposed rainwater harvesting sites on the basis of site suitability have been suggested. The goal of this study was to develop a robust methodology to extend these frameworks, which consider biophysical and socio-economic criteria only, to include ecological criteria in the site selection process. This is essential for ensuring environmental protection, maintaining biodiversity, water quality improvement, climate resilience, regulatory compliance and sustainability of the system. In this paper, the inter-relationships of ecological criteria are shown to be complex, with “independent” criteria affecting “mediator” criteria which then directly impact ecological standards, i.e. the “dependent” criteria such as number of aquatic organisms. It is shown how a robust combination of data analysis and expert opinion can be applied to determine relative weightings of the different ecological criteria, using temperature and light as examples of key independent criteria. The developed hybrid framework is applied to a case study of site selection in Erbil Province in Iraq, where both climate change and human actions have seriously reduced water supplies in the past twenty years, showing that inclusion of these ecological criteria changes the ranking of the sites compared to ranking without ecological considerations.