Conventional water distribution models are formulated under the assumption that water consumption or demand defined at nodes is a known value so that nodal hydraulic head and pipe flows can be determined by solving a set of quasi-linear equations. This formulation is well developed and valid for the scenarios that the hydraulic pressures throughout a system are adequate for delivery the required nodal demand. However, there are some scenarios where nodal pressure is not sufficient for supplying the required demand. These cases may include the planned system maintenances, unplanned pipe outages, power failure at pump stations, and insufficient water supply from water sources. In addition, some water consumptions like leakages are pressure dependent. In this paper, a robust and efficient approach for pressure dependent demand analysis is developed for simulating a variety of low pressure scenarios. A set of element criticality evaluation criteria is also proposed for quantifying the relative importance of the elements that may be out of service. The results are presented for the applications of the approach to the trivial systems and also to a large water system. It is demonstrated that great modeling performance and convergence rates are achieved for modeling pressure dependent demand conditions and evaluating the element criticality of the large water distribution systems.

ASCE is the original publisher of the article.

Reprinted with Permission from Zheng Yi Wu