RELIABILITY ASSESSMENT OF WATER-SUPPLY SYSTEMS WITH STORAGE AND DISTRIBUTION NETWORKS

The water supply system studied in this paper consists of a water trea tment plant, a ground-level storage, a pumping station, and a distribu tion network in series. Expected served demand is employed to measure reliability taking into account both insufficient heads and flows at i ndividual nodes in the network since it is the most important service level index provided to individual users. A basic method proposed is t o assume that the insufficient nodal head reduces the effectiveness of flow supplied at the node and that the authority provides the maximum service to customers so that the real-time pump and network flow oper ations maximize the effective served system demand. The average value of the maximum effective served system demand relative to the total sy stem demand over all system states is defined as system reliability, a nd the nodal reliability for each demand node is similarly defined. Th e Markov chain method introduced by Beim and Hobbs (1988) is employed to describe the evolution of the storage level over time so that the r eal-time pump and network flow operations can be accurately implemente d by solving a nonlinear programming model. Two example systems are pr esented to demonstrate numerically the advantage of the method propose d in its consideration of the distribution network and nodal reliabili ties.