**1. Introduction**

The typical high number of constraints and decision variables, the nonlinearity, and the non-smoothness of the head – flow – water quality governing equations are inherent to wa‐

An example of that is the least cost design problem of a water supply system defined as finding the water distribution system's component characteristics (e.g., pipe diameters, pump heads and maximum power, reservoir storage volumes, etc.), which minimize the system capital and operational costs, such that the system hydraulic laws are maintained (i.e., Kirchoff's Laws No. 1 and 2 for continuity of flow and energy, respectively), and con‐

Traditional methods for solving water distribution systems management problems used lin‐ ear /nonlinear optimization schemes which were limited in systems size, number of con‐ straints, and number of loading conditions. More recent methodologies are employing heu‐ ristic optimization techniques such as genetic algorithms or ant colony as stand alone or hy‐

This book addresses part of the above topics and is comprised of seven chapters: (1) Guide‐ lines for transient analysis in water transmission and distribution systems – identifying ex‐ treme impact failure scenarios to be considered in transient analysis design following by guidelines for surge control devices selection, location, and operation; (2) Model based sus‐ tainable management of regional water supply systems – an integrated optimal control wa‐ ter resources systems modeling approach for linking surface, groundwater, and water distri‐ bution systems analysis in a single framework; (3) Infrastructure asset management of urban water systems – an overview of infrastructure asset management methodologies for urban water systems with examples from the water industry; (4) Energy efficiency in water supply systems: GA for pump schedule optimization and ANN for hybrid energy prediction – a hy‐ brid genetic algorithm model for optimal scheduling of pumping units in water supply sys‐ tems; (5) Water demand uncertainty: the scaling laws approach – formation of scaling laws through combining stochastic models for water demand with analytical equations for ex‐ pressing the dependency of the statistical moments of the demand signals on the sampling time resolution and on the number of consumers; (6) Error in water meter measuring due to shorter flow and consumption shorter than the time the meter was calibrated – a practical hydraulic study on testing measurement errors due to shorter consumption times than the time the meters were calibrated for; and (7) Methodology of technical audit of water trans‐

mission mains – practical indicators for water mains rehabilitation decision making.

nal assistance throughout the entire preparation process of this book.

I wish to express my deep appreciation to all the contributing authors for taking the time and efforts to prepare their comprehensive chapters, and especially acknowledge Ms. Dra‐ gana Manestar, InTech Publishing Process Manager, for her outstanding kind and professio‐

Faculty of Civil and Environmental Engineering, Technion

Israel Institute of Technology, Haifa

**Avi Ostfeld**

ter supply systems planning and management problems.

brid data driven – heuristic schemes.

VIII Preface

**Acknowledgements**

straints on quantities and pressures at the consumer nodes are fulfilled.

Despite the addition of chlorine and potential flooding damage, drinking water is not gener‐ ally considered a hazardous commodity nor an overwhelming cost. Therefore, considerable water losses are tolerated by water companies throughout the world. However, more ex‐ treme variations in dry and wet periods induced by climate change will demand more sus‐ tainable water resource management. Transient phenomena ("transients") in water supply systems (WSS), including transmission and distribution systems, contribute to the occur‐ rence of leaks. Transients are caused by the normal variation in drinking water demand pat‐ terns that trigger pump operations and valve manipulations. Other transients are categorised as incidental or emergency operations. These include events like a pumping sta‐ tion power failure or an accidental pipe rupture by external forces. A number of excellent books on fluid transients have been written (Tullis 1989; Streeter and Wylie 1993; Thorley 2004), which focus on the physical phenomena, anti-surge devices and numerical modelling. However, there is still a need for practical guidance on the hydraulic analysis of municipal water systems in order to reduce or counteract the adverse effects of transient pressures. The need for guidelines on pressure transients is not only due to its positive effect on water loss‐ es, but also by the contribution to safe, cost-effective and energy-saving operation of water distribution systems. This chapter addresses the gap of practical guidance on the analysis of pressure transients in municipal water systems.

All existing design guidelines for pipeline systems aim for a final design that reliably resists all "reasonably possible" combinations of loads. System strength (or resistance) must suffi‐ ciently exceed the effect of system loads. The strength and load evaluation may be based on the more traditional allowable stress approach or on the more novel reliability-based limit state design. Both approaches and all standards lack a methodology to account for dynamic

© 2013 Pothof and Karney; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

hydraulic loads (i.e., pressure transients) (Pothof 1999; Pothof and McNulty 2001). Most of the current standards simply state that dynamic internal pressures should not exceed the de‐ sign pressure with a certain factor, duration and occurrence frequency. The Dutch standard NEN 3650 (Requirements for pipeline systems) includes an appendix that provides some guidance on pressure transients (NEN 2012).

controls; evaluation of normal operations and design of control systems. The approach has been applied successfully by Both Deltares (formerly Delft Hydraulics) and HydraTek and Associates Inc. in numerous large water transmission schemes worldwide. Especially the integrated design of surge provisions and control systems has many benefits for a safe, cost-effective and energy-efficient operation of the water pipeline system. Section 4

Guidelines for Transient Analysis in Water Transmission and Distribution Systems

http://dx.doi.org/10.5772/53944

3

summarises the key points of this paper.

**Figure 1.** Pressure Transient design (Jung and Karney 2009).

One of the earliest serious contributions to this topic was the significant compilation of Pe‐ jovic and Boldy (1992). This work not only considered transient issues such as parameter sensitivity and data requirements, but usefully classified a range of loading conditions that accounted for important differences between normal, emergency and catastrophic cases, and the variation in risk and damage that could be tolerated under these different states.

Boulos *et al*. (2005) introduced a flow chart for surge design in WSS. The authors address a number of consequences of hydraulic transients, including maximum pressure, vacuum conditions, cavitation, vibrations and risk of contamination. They proposed three potential solutions in case the transient analysis revealed unacceptable incidental pressures:


Boulos *et al*. list eight devices and summarise their principal operation. They do not provide an overview of the scenarios that should be included in a pressure transient analysis. Jung and Karney (2009) have recognised that an *a priori* defined design load does not necessarily result in the worst-case transient loading. Only in very simple systems can the most critical parameter combination can be defined *a priori* (Table 4). In reality, selecting appropriate boundary conditions and parameters is difficult. Further, the search for the worst case sce‐ nario, considering the dynamic behaviour in a WSS, is itself a challenging task due to the complicated nonlinear interactions among system components and variables. Jung and Kar‐ ney (2009) have extended the flow chart of Boulos *et al*. (2005), taking into account a search for the worst-case scenario (Figure 1). They propose to apply optimisation tools to find the worst-case loading and a feasible set of surge protection devices.

Automatic control systems have become common practice in WSS. Since WSS are spatially distributed, local control systems may continue in normal operating mode, after a power failure has occurred somewhere else in the system. The control systems may have a positive or negative effect on the propagation of hydraulic transients. On the other hand, the distrib‐ uted nature of WSS and the presence of control systems may be exploited to counteract the negative effects of emergency scenarios. Therefore, existing guidelines on the design of WSS must be updated on a regular basis in order to take these developments into account.

Typical design criteria for drinking water and wastewater pipeline systems are listed in section 2. Section 3 presents a systematic approach to the surge analysis of water systems. This approach focuses on guidelines for practitioners. The key steps in the approach in‐ clude the following: preconditions for the surge analysis; surge analysis of emergency sce‐ narios without provisions; sizing of anti-surge provisions and design of emergency controls; evaluation of normal operations and design of control systems. The approach has been applied successfully by Both Deltares (formerly Delft Hydraulics) and HydraTek and Associates Inc. in numerous large water transmission schemes worldwide. Especially the integrated design of surge provisions and control systems has many benefits for a safe, cost-effective and energy-efficient operation of the water pipeline system. Section 4 summarises the key points of this paper.

hydraulic loads (i.e., pressure transients) (Pothof 1999; Pothof and McNulty 2001). Most of the current standards simply state that dynamic internal pressures should not exceed the de‐ sign pressure with a certain factor, duration and occurrence frequency. The Dutch standard NEN 3650 (Requirements for pipeline systems) includes an appendix that provides some

One of the earliest serious contributions to this topic was the significant compilation of Pe‐ jovic and Boldy (1992). This work not only considered transient issues such as parameter sensitivity and data requirements, but usefully classified a range of loading conditions that accounted for important differences between normal, emergency and catastrophic cases, and

Boulos *et al*. (2005) introduced a flow chart for surge design in WSS. The authors address a number of consequences of hydraulic transients, including maximum pressure, vacuum conditions, cavitation, vibrations and risk of contamination. They proposed three potential

**2.** Modification of the system, including other pipe material, other pipe routing, etc.; and

Boulos *et al*. list eight devices and summarise their principal operation. They do not provide an overview of the scenarios that should be included in a pressure transient analysis. Jung and Karney (2009) have recognised that an *a priori* defined design load does not necessarily result in the worst-case transient loading. Only in very simple systems can the most critical parameter combination can be defined *a priori* (Table 4). In reality, selecting appropriate boundary conditions and parameters is difficult. Further, the search for the worst case sce‐ nario, considering the dynamic behaviour in a WSS, is itself a challenging task due to the complicated nonlinear interactions among system components and variables. Jung and Kar‐ ney (2009) have extended the flow chart of Boulos *et al*. (2005), taking into account a search for the worst-case scenario (Figure 1). They propose to apply optimisation tools to find the

Automatic control systems have become common practice in WSS. Since WSS are spatially distributed, local control systems may continue in normal operating mode, after a power failure has occurred somewhere else in the system. The control systems may have a positive or negative effect on the propagation of hydraulic transients. On the other hand, the distrib‐ uted nature of WSS and the presence of control systems may be exploited to counteract the negative effects of emergency scenarios. Therefore, existing guidelines on the design of WSS

Typical design criteria for drinking water and wastewater pipeline systems are listed in section 2. Section 3 presents a systematic approach to the surge analysis of water systems. This approach focuses on guidelines for practitioners. The key steps in the approach in‐ clude the following: preconditions for the surge analysis; surge analysis of emergency sce‐ narios without provisions; sizing of anti-surge provisions and design of emergency

must be updated on a regular basis in order to take these developments into account.

the variation in risk and damage that could be tolerated under these different states.

solutions in case the transient analysis revealed unacceptable incidental pressures:

**1.** Modification of transient event, such as slower valve closure or a flywheel;

worst-case loading and a feasible set of surge protection devices.

guidance on pressure transients (NEN 2012).

2 Water Supply System Analysis - Selected Topics

**3.** Application of anti-surge devices.

**Figure 1.** Pressure Transient design (Jung and Karney 2009).
