Reliability as tool for planning complex water resources systems

Failure of water resources systems, particularly water supply systems, may cause serious consequences in economical and social environment. So these systems have to fulfill high requirements of their functional safety. Although very important, that aspect of safety is not treated adequately in the phases of planning water distribution systems. That is why the aspects of overall water resources systems reliability evaluation, as well as the problems of allocation and reliability optimal system configuration, are considered. New methodology for water resources systems reliability evaluation is presented. Proposed methodology considers both: mechanical reliability (probability of pipe failure) and reliability of hydraulic parameters in nodes and links (pressure, velocity). On the base of this methodology NETREL and 2PFREL models were developed. These models are useful for determing reliability of systems with different configurations and complexity. Also, they make possible restriction of various hydraulic parameters and their values. Models were analyzed and verified on different water supply systems: regional and distribution, and gravity and pumping systems. Another important task, considered in the thesis, was problem of optimal reliability allocation. Different methods were analyzed, but particular point was focused on genetic algorithms. That method, coupled with the reliability evaluation methods, is an efficient tool for problems of water resources systems optimal reliability allocation. This methodology provides performing optimization in real time and results that are usually the global optimum of the considered problem. Mechanical characteristics of pipes, failure and repair rates, are very important for system's overall reliability. These rates were considered and critically analyzed. Methods for planning operative monitoring-information system are proposed. Such a system allows better monitoring and management, reduction of repair time, which leads to higher values of system's overall reliability. Pipes failure and repair rates for Belgrade water supply system were analyzed and used as the base for evaluation of presented models