Evaluating Water Demand Shortfalls in Segment Analysis E. Creaco & M. Franchini & S. Alvisi Received: 8 October 2010 / Accepted: 5 March 2012 / Published online: 21 March 2012 # Springer Science+Business Media B.V. 2012 Abstract In this paper, two procedures for assessing water demand shortfalls following segment isolation are compared. The first (topological) procedure is based on a simple topological network analysis, and identifies the water demand shortfall as the water demand (under normal operational conditions) relative to the directly and/or indirectly isolated segment (s). The second (hydraulic) procedure is based on a pressure-driven hydraulic simulation of the network after segment isolation. Each of the two procedures was applied to two case studies, and the reliability (expressed in terms of maximum D max and weighted average D water demand shortfall) and economic burden (expressed in terms of number N val or cost C val of installed valves) of the resulting isolation valve system solution were compared. As a whole, the results show that network analysis and redesign are affected by the choice of the global variables (D max or D) used to characterize the demand shortfalls in network segments. Analysis of the case studies is followed by a discussion of the rationale behind the choice between the two procedures, which needs to balance accurate demand shortfall characterization with limited computation times, particularly in the multi-objective design stage. Keywords Valves . Water distribution systems . Multi-objective algorithm . System reliability . Pressure-driven 1 Introduction In recent decades, the scientific literature concerning the design and management of water supply systems has addressed aspects related to the concept of network reliability , i.e. the ability of a distribution system to satisfy, in both quantitative and qualitative terms, users’ Water Resour Manage (2012) 26:2301–2321 DOI 10.1007/s11269-012-0018-0 E. Creaco (*) : M. Franchini : S. Alvisi Dipartimento di Ingegneria, Università degli Studi di Ferrara, Via Saragat 1, 44122 Ferrara, Italy e-mail: enrico.creaco@unife.it M. Franchini e-mail: marco.franchini@unife.it S. Alvisi e-mail: stefano.alvisi@unife.it