Rehabiliting intermittent water supply systems through a multi-objective optimization method based on hydraulic simulations

Intermittent water systems supply hundreds of millions of people in low- and middle-income countries, a number expected to increase due to climate change, urbanization, and water scarcity. The current study presents a pragmatic method for the rehabilitation of complex intermittent systems through the definition of multiple strategies (i.e. controls and investments) to be applied over time. The method proposed is based on the combined use of EPANET 2.2 software for hydraulic modelling and MATLAB® programming software, and consists of several phases. First, the topological and hydraulic analysis of the network is conducted with the aim of identifying its main vulnerabilities. Second, optimal intervention strategies for network initial layout and subsequent rehabilitation (i.e., control modifications and investments) are identified through a multi-phase method based on engineering judgment. The effects of different intervention strategies are then quantified by means of a series of service indicators reflecting the multi-objective nature of the problem. Finally, the optimal solution of the problem is found by iteratively altering the most effective solution previously met. Within the framework of the Battle of Intermittent Water Supply, the method was applied to a realistic case-study water distribution network consisting of more than 3,000 pipes and it allowed to obtain an effective intervention solution for the reduction of the critical issues related to the system.