Computerized evaluation of water-supply reliability

The application of network reliability to maintenance and rehabilitation of water distribution systems is discussed. An algorithm converts a distribution system into a stochastic network in which arcs represent components with random life, and nodes represent demand points (junctions) between the components. Water supply reliability at a demand point is the reliability of the subnetwork defined by the source and the demand point. A simple reliability measure based on network connectivity is used to compute subnetwork reliability by the method of minimal pathsets or minimal cutsets. The point reliability values at the demand points can be used to draw a reliability surface; that surface offers a new approach to addressing water-supply infrastructure maintenance and rehabilitation issues. The methodology is illustrated by analyzing a case-study water system using a specially devised computer program. The proposed algorithm is not necessarily the most efficient, but is certainly the simplest. The reliability measure is based on water availability only, regardless of its quantity or quality