Influence of Pipe Discharges on Cost and Reliability of Looped Water Distribution Networks

Looped water distribution networks (WDNs) are preferred over branched networks mainly as they provide alternate paths in case of failure of any one of the pipe in the network. However, the optimal design of looped WDNs for minimum cost results in converting them into a branching configuration thereby removing redundancy due to loop-forming links. Therefore, performance of a looped WDN under abnormal conditions such as those arising due to component failure or uncertainty in various input parameters is assured through various parameters such as reliability, flexibility, redundancy, robustness, resilience, etc. The optimal design of a looped WDN with constraints of minimum pipe flows to assure looped nature of network provides a minimum cost-less reliability network. A study is carried out to understand the effect of pipe discharges on network cost and reliability with a multiple-pipe single-loop network and a multiple looped network. Pipe discharges are represented through statistical parameter variance and reliability is quantified through demand satisfaction ratio, obtained by considering all single-pipe failure conditions. Graphical representation of network cost and reliability showed that network reliability is maximum which is achieved through minimum cost when variance in pipe discharges is minimum, as any change in pipe-discharges results in either increase in cost with decrease in reliability, or decrease in both cost and reliability. Thus, a flow distribution in the network corresponding to minimum variance is observed to provide maximum reliability in the design with minimum cost.