One of the perplexing conundrums in the provision of rural water and sanitation in developing countries is understanding why these systems fail or thrive. With the various institutional, technical, socioeconomic, and environmental risks intertwining with the success or failure of water and sanitation systems, the identification of the explanatory factors and complexities that explain such outcomes becomes crucial for both policy and academic reasons. In the presence of important knowledge gaps in the understanding of those factors and complexities, this thesis presents a body of work that contributes to understanding specifically the institutional and management issues that produce the desire changes in promote systems functioning and performing well over time. Specifically, this study presents an overview and meta-analysis of the existing literature on the impacts of water supply, sanitation and hygiene interventions. In particular, the core part of this study utilized a meta-analysis technique to quantitatively explore the main research areas that analyse the effectiveness of Water Supply,Sanitation and Hygiene interventions. Also, a this study contains both correlational and causal evidence on the main drivers of rural water and sanitation systems’ sustainability over time. The correlational analysis identified the institutional, governance and operational management factors that explain water and sanitation systems sustainability over time. In subsequent sections of this thesis the causal evidence is presented based on a Randomised Control Trial (RCT) to explore the main factors that explain rural water systems’ sustainability through a large-scale training program to community water boards in a developing country (Nicaragua). The RCT showed a causal attribution between the training program and the way in which rural water system performed in multiple dimensions On average, in line with the project indicators, Community Water Boards (CAPS) in treatment communities experienced a statistically significant increase in their institutional management, financial solidity, in their attention to operation and maintenance of the water basin, and in their attention to the water source. In particular, CAPS management of service providers increased by 0.41 standard deviations in the treatment group compared to the control, CAPS financial solidity increased by 0.39 standard deviations in the treatment group compared to the control, CAPS attention to operation and maintenance of the water basin increased by 0.33 standard deviations compared to the control, and CAPS adequate protection of the water source increased by 0.24 standard deviations in comparison to the control group. There were measurable decreases in diarrhoea, but these were only mildly statistically significant. The largest household-level effect is for sanitation indicators, where treatment households experienced increases in access to improved sanitation, increases in access to improved, unshared sanitation, and decreases in levels of open-defecation. The results are not negligible and are pointing in the right direction with respect to the overall objective of the program evaluated (The Rural Water Supply Sustainability Program—PROSASR). However, further research would be needed to assess whether these effects are long-lasting and assess the relationship between sustainability of rural water systems and these types of CAPS training programs. In striving towards attaining universal access to safely managed services by 2030, significant research is needed to understand the effectiveness of capacity building of service providers to ensure rural water supply and sanitation sustainability. Thus, it is necessary to develop a comprehensive research on the supply-side WASH interventions with various techniques including panel data and systems-based analysis,
