4.1 Integrated large-scale suitability analysis
The mixed-methods approach, presented in this study for sand dams siting, represent a valuable methodological contribution for a broader set of water harvesting practices. In fact, the range of integration of biophysical and socio-economic assessments is still largely underexplored, although widely recommended (Ammar et al., 2016; Bulcock and Jewitt, 2013; Castelli et al., 2022), and most water harvesting siting approaches are relying only on biophysical MCDA. The limitations of such top-down MCDA approaches are multiple. First, MCDA is very sensitive to the input data, which are often scares or have inadequate resolution in most drylands, and particularly in Angola (Amado et al., 2020). This affects the quality of the results, requiring a careful validation or, preferably, an integration with local analysis. For example, Forzieri et al. (2008), Fuentes and Vervoort (2020) and Vishwakarma et al. (2021), among others, developed analyses for similar infrastructures based on engineering and technical perspectives, recognized their limitations when the results were validated, and stressed the importance of incorporating socio-economic aspects related to local and regional dynamics, which are difficult to measure without an interdisciplinary perspective. Bulcock and Jewitt (2013) concluded that the existing guidelines for determining suitable locations for water harvesting base on biophysical MCDA tend to represent only the optimal conditions, claiming that complementing the assessment with a local participatory approach, like the one presented in this study, can be instrumental.
In fact, especially when imbedded in broader water resilience strategies for small communities, following top-down approaches fail to consider knowledge and motivation to adopt the proposed technologies, as well as other political and socio-economic local circumstances that influence adaptation choices (Grum et al., 2016, Van Aalst et al., 2008). debating with the communities and facilitating their internal discussions from the early siting phase can increase local awareness about long-term water supply needs and water harvesting options (Rajabu, 2005; Everard, 2019) and allow the researchers to incorporate useful criteria to siting modeling. This has resulted in increased integration of biophysical and sopcio-economic components in suitability analysis at different scales, from local to national and even global (Al-Adamat et al., 2012; Piemontese et al., 2022, 2020), although the depth of integration between the social and the ecological components varies (Ammar et al., 2016). These integrated assessments often rely on indicators, which provide a quantitative and scalable measure. For example, Piemontese et. al. proposed a social-ecological systems approach for a global suitability of water harvesting using both biophysical and socio-economic indicators. At the local scale, Lasage and Verburg (2015) validate and recommend a similar mix of biophysical and socioeconomic conditions to be considered in order to focus on pertinent characteristics and to ensure an integrated approach when evaluating water harvesting investments.
Our contribution adds to this literature by providing a practical framework to explicitly integrating local knowledge, which is a major frontier in integrated assessments (Al-Adamat et al., 2012; Hart and Mouton, 2005; Robinson et al., 2016). Also, particularly relevant is the application to sand dams, for which such integrated approach was still missing, although highly recommended by experts (Castelli et al., 2022). Our approach thus contributes to expanding the frontiers of knowledge integration on water harvesting implementations and providing a specific guidance on sand dams large-scale siting to increase the spread and the applicability of such a promising technology.