Mechanical and Hydraulic Reliability Estimators for Water Distribution Systems

Reliability of water distribution systems is typically divided into mechanical and hydraulic reliability. This paper introduces two reliability surrogate measures: the mechanical reliability estimator and the hydraulic reliability estimator. These estimators were developed based on simplifications of a broader definition of stochastic reliability and were tested in the multiobjective design optimization of the Hanoi and Fossolo benchmark networks. The numerical values of the estimators were compared with existing reliability surrogate measures (the residence index, the network resilience index, and flow entropy) through correlation analysis. Results showed that the proposed estimators concur with existing optimization algorithms. They also show that previous indexes correlate with at most one of the types of reliability, while a trade-off between them seems to appear, especially in one of the study cases.