Extended Global-Gradient Algorithm for Pressure-Dependent Water Distribution Analysis

Conventional water distribution models are formulated under the assumption that water consumptions or demands defined at nodes are known values, allowing nodal hydraulic heads and pipe flows to be determined by solving a set of quasi-linear equations. This formulation is well developed and is valid for the scenarios in which the hydraulic pressures throughout a system are adequate for delivering the required nodal demands. However, there are some scenarios where nodal pressure is not sufficient for supplying the required demand. These cases may include planned system maintenances, unplanned pipe outages, power failures at pump stations, and insufficient water supply from water sources. In addition, some water consumptions, such as leakages, are pressure dependent. This paper generalizes a robust and efficient approach for pressure-dependent water distribution analysis as a unified loop-node formulation. Nodal heads and flows are simultaneously solved by improving the global-gradient algorithm. The proposed approach has been applied to a pressure-deficient benchmark system, the criticality analysis of a small water system, and also to a large real water system. The paper demonstrates that good modeling performance has been achieved for simulating pressure-dependent demand conditions and evaluating the criticality of real water systems.