predicting deficient condition performance of water distribution networks

a water distribution network is subjected to various abnormal conditions such as pipe breaks, pump failures, excessive demands etc. in the design period. under such conditions, the network may not be able to meet required demands at desired pressures, and becomes deficient. traditional network analysis assumes nodal demands to be satisfied and available nodal pressures are calculated. however, assumption that demands are satisfied at all nodes is not true under deficient conditions. therefore, under deficient conditions nodal demands and pressures are considered simultaneously through head-flow relationships to calculate available nodal flows. this type of analysis that determines available flows is termed as node flow analysis or pressure-driven or dependent wherein, outflows are considered as function of available pressure. various node head-flow relationships (nhfr) have been suggested by researchers to correlate available flow and available pressure based on required flow and required pressure. methods using these nhfrs have been classified herein as direct and indirect approaches. applications of these approaches have been shown with two illustrative examples and results are compared.