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Planned (e.g., regular maintenance) and unplanned (e.g. pipe burst) interruptions occur regularly in water distribution systems leading to their reduced performance. This paper presents an extended period simulation model capable of assessing system’s performance under these conditions. The extended period simulation model is based on the recently developed steady-state pressure driven hydraulic model and is capable of calculating pressures, flows, and hence actual water demands delivered under modified network topology conditions (caused by the use of isolation valves). The model is accompanied by several reliability indicators which can be used to assess system’s performance under interruptions. The above-mentioned methodology is demonstrated on a real-life case study in Italy. The role of isolation valve design and uncertainty in valve operability is analyzed and discussed. The case study results obtained demonstrate that the least cost design/rehabilitation of water distribution systems is likely to result in unreliable systems if the actual network configurations obtained by closing isolation valves in abnormal working conditions are not taken into account. [ABSTRACT FROM AUTHOR]

A common method for assessing the energy potential of hydropower systems in Iran is the sequential streamflow routing with control on the energy-yield reliability. The method results in developing a reliability-based simulation (RBS) model that is used to analyze single-reservoir hydropower systems. In most of the cascade hydropower systems in the country, a single-reservoir RBS model is usually employed in the design and operation of each of the systems reservoirs. This paper presents a multireservoir RBS model considering the integrated operation of the systems. The model employs the general algorithm of the single-reservoir RBS model; however, with a single-period optimization submodel in determining releases from reservoirs during the system simulation. The objective function of the submodels minimizes the sum of reservoir releases and/or maximizes the sum of reservoir storages in each of the time periods, subject to a reliability constraint on the system’s energy yield. The single and multireservoir RBS models are applied in the Khersan hydropower system located in Iran as a case study. The multireservoir RBS, compared to the single-reservoir model, results in 7.9% excess firm-energy yield in reliability of 90%. [ABSTRACT FROM AUTHOR]

In this paper, the authors propose a new approach, the simulation–optimization method, to solve a nonlinear contaminant-source and release-history identification problem for a complex water distribution system. This approach is based on optimization analysis, using the EPANET water distribution system model as a simulator. In this approach, EPANET is used to generate concentrations at arbitrarily selected monitoring locations by specifying release histories of potential contaminant sources that are arbitrarily located within the water distribution system. This information is used in a continuous optimal predictor–corrector algorithm to identify the sources and their release histories. Throughout the simulation sequence, the water distribution system being studied is assumed to operate under known hydraulic operational patterns. The optimization model that is used as a corrector to estimate the release histories of the contaminant sources is designed to identify the similarity between the simulation response and measured data at monitoring locations. This information exchange is developed as a closed-loop system resulting in a convergent algorithm. Three scenarios, derived from the publicly documented Dover Township (Toms River), N.J., water-distribution system are tested using the proposed approach. Results show that the approach is effective, efficient, and robust in identifying locations and release histories of contaminant sources. [ABSTRACT FROM AUTHOR]