A water distribution network (WDN) is an essential component of an urban water supply scheme to deliver safe and adequate water to consumers under various operational conditions. This study focuses on the performance evaluation of an urban WDN using fuzzy logic-based aggregation of reliability, resilience, and vulnerability indices. To assess the individual performance indicators, this study advocates the pressure-dependent analysis (PDA) for the hydraulic simulation. Furthermore, it advocates a fuzzy rule-based aggregated performance index (API) that will deliver the outcome in linguistic form and help the decision-maker to prioritize the maintenance of the WDN. The proposed method is illustrated with the help of a real-time WDN for part of Dire Dawa city in Ethiopia. It has been found that the API values for this network are 0.721 and 0.624, respectively, under normal and abnormal conditions, which are just satisfactory. It has been noticed that nodes J4, J44, J47, and J49 are critical from the overall low API. Efforts should be made to improve the hydraulic and residual chlorine conditions at these nodes to increase the API. It is felt that such a methodology will help the decision-makers in improving the performance of an existing urban WDN.

Rapid urbanization in developing countries has imposed threats and challenges to basic urban infrastructures like drinking water, transportation, and energy systems. The existing urban drinking water systems (UDWS) are highly stressed and unsustainable, particularly under changing hydroclimatic conditions, population growth, changing socioeconomic conditions, government decisions, and various policies. This study focuses on the complexities of UDWS in Sub-Saharan African countries, especially in Ethiopia. The objective of this study is to investigate the issues and challenges of urban drinking water systems (UDWS) in Ethiopia, specifically, to assess the gap between water supply and demand, water loss/non-revenue water, environmental, technical, institutional, and governance, etc. and propose sustainable interventions to deal with such issues so as to improve. For this purpose, a mix of methods involving primary data (including key informant interviews, field observations, and field measured data) and secondary data (including published articles, books, various reports, and design documents), as well as various computer-aided applications (mainly, ArcGIS and WaterGEMS) are used to collect data. The issues are deliberated through the UDWSs of Addis Ababa, Adama, Mekelle, and Dire Dawa cities in Ethiopia. Complexities like water shortage, high and low pressure in the water distribution network (WDN), non-revenue water (NRW)/water loss, source pollution, ineffective policies and governance, and weak institutions are the main challenges to Ethiopian cities' water utilities. Further, the case study noticed that in Addis Ababa alone, potable water is only accessible to 66% of the city population. A significant water supply deficit was observed in Mekelle city, where only half of the city population has access to potable water from the system. Additionally, in Addis Ababa, Adama, Mekelle, and Dire Dawa, above 35% of the freshwater produced is either NRW, unaccounted for, or lost, which is significantly higher than the upper 25% limit suggested by the World Bank. Therefore, it is recommended to adopt certain sustainable interventions, such as integrated water resource management, installing appurtenances like pressure-reducing valves, check valves in the WDN, controlling and monitoring of WDN through supervisory control and data acquisition and Internet of Things, effective and long-term planning and policy, etc. It is felt that the study will help the decision-makers and the operators of the UDWS utilities to run the water supply schemes in a sustainable manner. Supplementary Information The online version contains supplementary material available at 10.1007/s10668-022-02901-7.

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Pipe and isolation valve failure in an urban water distribution network (WDN) causes service interruption to the water users. It is important to identify and prioritize the maintenance of the most severe impact-causing pipes and valve failures. This study investigates the impacts of such failures in terms of the number of isolation elements, the number of affected customers, and the supply shortfall (SS). The study proposes an impact-based prioritization model for pipe and isolation valve repair/replacement in a WDN using the analytic hierarchy process (AHP). The WDN modeling, simulation, and generation of segments are carried out using the WaterGEMS software. The proposed methodology is illustrated with the help of a real-time WDN of Dire Dawa city in Ethiopia. Through the study, it is noticed that each valve/pipe failure has varied impacts and gets reduced with the increase in valve density. Further, the SS is the most important parameter for prioritizing the maintenance. The failure of the valves and pipes significantly affects the system's performance and should be repaired/replaced on priority basis. It is hoped that the proposal will help the decision-makers in the optimal utilization of limited resources available for repair/ maintenance.

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