Analysis Of Water Distribution Networks Research Articles

Improvement of the Segment‐Valve Model for Solving the Valve Isolation Problem and Evaluating the Reliability of Water Distribution Networks

AbstractThe segment‐valve graph model is widely used in the reliable evaluation of water distribution networks (WDNs). However, as an undirected graph, a segment‐valve graph does not express the upstream‐downstream relationships between segments, which hinders finding valves that need to be closed when a pipe bursts and the water outage region. Therefore, in this paper, directed edges applied to a segment‐valve graph are introduced to demonstrate the downstream segments of critical segments, and an improved segment‐valve graph with flow directions is proposed. The improved model is used to solve the valve isolation problem and evaluate the reliability of WDNs. The results show that the improved model can determine that the valve needs to be closed more quickly when a pipe burst occurs. In addition, we improve the traditional classical indicators based on the segment‐valve graph model. The new indicators based on the improved model can reflect the actual impact and the disposal difficulty of pipe network accidents more accurately and clearly. The proposed method can play a critical role in accident processing and reliability analysis of WDNs.

An assessment of the artificial modelling elements approach to the pressure-driven analysis of water distribution networks

Abstract EPANET 2.2 is a newly introduced upgraded version of EPANET 2 that can be used for both pressure-driven analysis (PDA) and demand-driven analysis (DDA) of water distribution networks. Moreover, it has certain limitations concerning the minimum and required pressure head parameters used for PDA, which leads to inaccurate simulation results. Another limitation of the PDA option of EPANET 2.2 is its inability to simultaneously consider pressure-dependent demands with pressure-independent fire demands. In this article, the reason for the spurious convergence is identified, and it is shown that the spurious convergence of EPANET 2.2 can be addressed by extending the energy balance convergence criterion to include the virtual demand links employed in the EPANET 2.2 formulation of PDA. On the other hand, interest in the methods that use artificial modelling elements in EPANET 2 for PDA is increasing rapidly. The implementation of the method presented in this paper (termed the alternative PDA approach) allows an extended period simulation of large networks with complex demand patterns, multiple tanks, reservoirs, pumps, valves, and thousands of pipes. Two benchmark networks and two real-world networks were analysed by both the alternative PDA approach and EPANET 2.2 and the results were compared.

A parallel computing architecture based on cellular automata for hydraulic analysis of water distribution networks

Water distribution networks (WDNs) are one of the largest infrastructures in society. Various methods for formulation and hydraulic analysis of water distribution networks, including numerical and non-numerical methods, have been previously proposed. Due to the complexity, the nonlinearity of the hydraulic equations of water distribution networks, and the need for multiple executions and uncertainties in parameters, solving the hydraulic model of water distribution networks has high time complexity. In this paper, a parallel computational architecture based on the concept of cellular automata is proposed to accelerate the numerical solution of the steady-state water distribution network model. Taylor series is proposed to solve hydraulic equations. The presented architecture was implemented as a parallel hardware platform on a field-programmable gate array. The performance of the proposed method was compared with EPANET software for networks with different complexities and topologies. The results show that the proposed parallel algorithm can accelerate the hydraulic analysis of regular water distribution networks up to 700 times and 250 times for small and large networks, respectively.

Optimal design and cost analysis of water distribution networks based on pressure-dependent leakage using NSGA-II

Leakage from water distribution networks (WDNs) is inevitable. Therefore, during design a WDN, engineers add a percentage of each nodal water demand as leakage discharge to total node demand. The amount of leakage depends on the pressure, which is not known at the design stage. Considering a constant percentage of node demand in lieu of its leakage makes the problem worse. In this study, the effect of leakage on the optimal WDN design was investigated by developing the matrix form of the gradient algorithm while accounting for leakage using the pressure-dependent model. Non-dominated genetic algorithm version II (NSGA-II) was used as the optimization engine with two objectives which includes minimizing the network construction cost and minimizing the total network pressure deficiency. Two well-known two- and three-loop WDNs in literature were studied. The results indicated that the pressure-dependent leakage varies between 12.9 and 29.44% of the node demand while the network construction cost stays the same if compared with the fixed percentage leakage model, and the construction cost would increase by 17–31%, if leakage is not accounted for. This is expected the optimized diameters and hydraulic characteristics of the networks being affected by the leakage calculation method.

Topological analysis of water distribution networks for optimal leak localization

This paper introduces two methodologies to provide an optimum sensor deployment layout, one based on a model-based approach and the other entirely data-driven. The first method is formulated as an integer optimization problem, an optimization criterion consisting of minimizing the average topological distance. The second method is a new methodology to provide an optimum sensor placement regarding how many sensors to install without using hydraulic information but just exploiting the knowledge of the topology of the Water Distribution Networks. The method uses the Girvan-Newman clustering algorithm to ensure complete coverage of the network and the study of the installation of pressure sensors in the central nodes of each group, selected according to different metrics of topological centrality. The approach is illustrated in the Modena network.

WDN-tailored Complex Network Centrality Metrics for water distribution networks domain analysis

Water Distribution Networks (WDNs) are spatially organized infrastructures, whose hydraulic behavior greatly depends on their connectivity properties, i.e., the topological domain. The Complex Network Theory (CNT) provides a wide range of useful functions and metrics that have been tailored for identifying WDNs behavior, even before using hydraulic models. This work exploits the recent studies on the WDN domain, which couple the CNT metrics of centrality tailored for WDN with the intrinsic relevance of the spatial elements of the networks. The study accounts for various combinations of metrics and intrinsic relevance functions aimed at supporting WDN analysis for operational and management tasks. A Digital Water Service (DWS) is used to enable technicians and water companies to replicate the same domain analysis in the ongoing context of digital transformation in WDN sector.

Effect of variation of empirical exponent coefficient values in water distribution network analysis

The water distribution network supplies water to consumer to fulfill demands at desired pressure. Due to pressure deficient conditions pressure fall below minimum required which ultimately lead to reduction in flow supplied to consumer. The water distribution network is said to be pressure deficient, if the pressure head in each node is less than the required head. Adding artificial element approach for predicting partial flow at demand node in pressure deficient condition is used by many researchers. The objective of study is to investigate effect of variation in empirical exponent coefficient on emitter exponent, pressure and actual demand at demand node. The steady state simulation is carried out for case study network with pressure deficient node as emitter node using Fictitious component free – Pressure Deficient Network Algorithm. The emitter coefficient formula, derived from Wagner’s equation is used for predicting actual demand under pressure deficient condition. The value of emitter coefficient depends on emitter exponent coefficient value, which is calculated using empirical exponent coefficient. The study is carried out for three different values of empirical exponent coefficient 0.5, 1, 1.5, 1.852, 2 and 2.5 respectively. The simulation analysis shows that as empirical exponent increases emitter exponent decreases, pressure decreases and actual demand at nodes increases. This study can be useful in calculating resilience index, which is measure of average efficiency of water distribution network under pressure deficient condition.

Analysis of Water Distribution Network Using Epanet for Normal and Leakage Condition and Its Effect on Pressure

Abstract: Water distribution network is a system of engineered hydrologic and hydraulic component which supplies water from the source to the required area. In the design of water distribution network, it is crucial that the network supplies the forecasted demands with enough residual heads at all nodes of the network during the entire design period. However with the increasing change in future scenario, either the nodal demands change or the water distribution network falls short to meet the increasing demands. Therefore, we require a proper analysis of water networks to strengthen them for future. In situations like this, softwares play a major role in analyzing water distribution network to make it work as per the design. The present study is an effort to analyze the water supply network using available software, it proposes hydraulic simulation model for water distribution network analysis and comparison of results.

Topological and hydraulic metrics-based search space reduction for optimal re-sizing of water distribution networks

Abstract Pipe re-sizing of water distribution networks (WDNs) aims at improving the service performance to the required level, while minimizing the cost of replacing pipes in the network. The main challenge comes from the identification of the most effective pipes to re-size from a large number of interacting components. Performing a global search over all pipes in large WDNs does not guarantee a feasible and efficient solution due to the enormous search space, even by employing advanced algorithms, e.g., evolutionary algorithms. This paper proposes a novel method to reduce the search space for optimal re-sizing based on topological metrics from Complex Network Theory and hydraulic metrics, while providing suboptimal solutions comparable to the full search solutions, i.e., considering all pipes as candidates. The topological metrics are based on the edge-betweenness tailored for WDN analysis. Hydraulic metrics are unit head loss and flow rates of pipes computed based on simulation of the WDN in the current configuration. The optimal re-sizing plans obtained, particularly those using edge betweenness, were tested on a real WDN. The results are comparable with the full search solutions but they are much more efficient to obtain and require replacing mostly contiguous pipes, i.e., easier for practical fieldwork.

Erratum for “Technique for the Pressure-Driven Analysis of Water Distribution Networks with Flow- and Pressure-Regulating Valves” by Nikolai B. Gorev, Vyacheslav N. Gorev, Inna F. Kodzhespirova, Igor A. Shedlovsky, and P. Sivakumar

Erratum for “Technique for the Pressure-Driven Analysis of Water Distribution Networks with Flow- and Pressure-Regulating Valves” by Nikolai B. Gorev, Vyacheslav N. Gorev, Inna F. Kodzhespirova, Igor A. Shedlovsky, and P. Sivakumar

A systematic framework for dynamic nodal vulnerability assessment of water distribution networks based on multilayer networks

Nodal demands vary throughout the day, as such any vulnerability analysis based on static networks, which considers daily average demands cannot realistically represent the criticality of nodes in the network. This study presents a systematic framework, which couples multilayer networks, structural reducibility and a Demand Adjusted Vulnerability Measure for dynamic nodal vulnerability assessment of water distribution networks (WDNs) under extended period simulation. Within this framework, we present the novel idea of characterizing the dynamics of WDNs with multi-slice networks, which captures the state of the network within a predefined temporal window taking into consideration the directional flow in pipes and the operational status of pumps, valves etc. Using a benchmark WDN, Net 3, as a case study we have demonstrated the importance of demand variations and operational status of various components, no matter how minuscule their operational time, on nodal vulnerability assessment in WDNs. The results indicated that the framework evaluates the criticality of all types of nodes, even intermediary nodes with zero base demand, within any temporal window much more realistically than conventional vulnerability analysis methods based on single (static) networks. Structural reducibility unearthed correlations between the operational status of source nodes and pumps on the general dynamics of the distribution system. The multilayer framework opens a new frontier in vulnerability analysis of WDNs and could serve as a tool for stakeholders in accessing node criticality, impact of various failure scenarios and optimal scheduling of maintenance routines.

Pressure Flow–Based Algorithms for Pressure-Driven Analysis of Water Distribution Networks

In recent years, pressure-driven analyses of water distribution systems using pressure-flow relationships (PFRs) were shown to be more computationally efficient than those based on flow-pressure relationships (FPRs), such as the widely used Wagner equation and various spline approximations. Using a PFR enhances the convergence properties of the Newton–Raphson method used by most water distribution network (WDN) solvers. This paper derives a new way of incorporating a PFR into the classical Todini and Pilati global gradient algorithm (GGA). The convergence properties of the resulting solution algorithm are compared with those from two other existing PFR algorithms, EPANET 2.2 and the active-set method (ASM), as well as from a conventional flow-pressure–based algorithm on a number of different networks of varying size.

Fractality in water distribution networks: application to criticality analysis and optimal rehabilitation

ABSTRACT Fractals have been identified as a common feature in many natural and artificial networks that exhibit self-similarity of the topological patterns, i.e. different parts of the system have similar structures to each other as well as to the whole system. This study investigates the fractality in water distribution networks (WDNs) and the application of the fractal property in WDNs analysis. Specifically, we explore the existence of fractal topological patterns in eight real-world WDNs of different complexities by using the box-covering algorithm. The results demonstrate all of the studied WDNs are fractal. Moreover, the application of the fractal property is demonstrated via critical pipe identification and optimal rehabilitation of benchmark real-world WDNs. All results show that the fractal-based approach can achieve better or equally good solutions compared with conventional methods in a much more efficient way, e.g. via automation of some processes or significant reduction in the search space/components to consider.

Nodal vulnerability assessment of water distribution networks: An integrated Fuzzy AHP-TOPSIS approach

Water Distribution Networks (WDNs) ensure reliable water supply to consumers which depends largely on joint and well-coordinated functioning of all diverse facets and components of the WDN. Failure of a vital component has catastrophic consequences and could impair the overall performance of the distribution system. This study presents an integrated Fuzzy AHP-TOPSIS framework that couples selected topological, hydraulic and water quality parameters to holistically assess nodal vulnerability of WDNs even under conflicting priority ranking of the methods considered. Within this framework, we harmonize the unique strengths of Closeness Centrality, Demand Adjusted Closeness Centrality and a Water Quality Index to accurately characterize the vulnerability of demand nodes. The proposed framework is validated on two case studies. The results indicate the ability of the integrated framework to accurately rank demand nodes, differentiate between nodes with the same base demand and distinguish between sink nodes based on water quality. The vulnerability indexes presented by the framework cannot be exhaustively explained by any of the original methods, an indication that the integrated framework provides new information in vulnerability analysis of WDNs. The framework could serve as a tool for water engineers in the analysis of critical nodes, scheduling of maintenance strategies and the assessment of failure impact on water distribution networks.

Technique for the Pressure-Driven Analysis of Water Distribution Networks with Flow- and Pressure-Regulating Valves

AbstractThis technical note presents a technique for the pressure-driven analysis (PDA) of water distribution networks with flow- and pressure-regulating valves. The technique is a combination of a...

Forecasting the Impact of Population Growth on Robustness of Water Distribution Networks: A System Dynamics Approach

Robustness analysis of water distribution networks (WDNs) has recently come to prominence in the research literature. While the robustness analysis is garnering much attention, there is a knowledge gap surrounding the forecasting of robustness in response to changes in the parameters involved in the analysis, such as water demand and population growth. To fill this gap, this article looks at the robustness of WDNs through the lens of the system dynamics (SD) modeling approach. The objective of this article is to design a dynamic model for the robustness analysis of WDNs that can be updated as its constituent variables change over time. The propose SD modeling approach is developed for a real-world case study of an Australian town. Model simulations are performed for three scenarios designed to forecast the effects of different population growth rates on robustness. The results showed that uneven demand distribution forced by uneven population growth has a strong influence on the robustness of WDNs. Furthermore, the simulation results highlighted the importance of considering the future development pattern of suburbs at the inception of the city development planning.

The emergence and evolution of reliability theory for water distribution networks

PurposeAs a response to the growing operational and disruptive threats to water distribution networks (WDNs), researchers have developed a vast array of methods for the reliability analysis of WDNs. In order to follow this growing number of methods, this paper reviews and documents in one place the historical developments in the reliability analysis of WDN.Design/methodology/approachA systematic literature review (SLR) is carried out to summarize the state-of-the-art research on reliability analysis of WDNs. In conducting this systemic literature review, the authors adopted an iterative approach to define appropriate keywords, analyze and synthesize data and finalizing the classification results.FindingsFirst, the hydraulic approach to reliability analysis is currently pervasive, and relatively little academic research has addressed the topological reliability analysis of WDNs. Second, in order to provide a comprehensive picture of the network reliability, a different approach that integrates topological and hydraulic attributes seems a more effective method. Third, the conventional reliability analysis methods are only effective for demonstrating a snapshot of these networks at a given point in time. The availability of methods that enable researchers to evaluate the reliability in response to changes in its variables is still a major challenge.Originality/valueThe present paper facilitates future research in the reliability analysis of WDNs by providing a source of references for researchers and water utilities. Further, this article makes a contribution to the literature by offering a roadmap for future reliability analysis of WDNs by reviewing the evolution of the current reliability analysis methods throughout history.

Effects of Non-Zero Minimum Pressure Heads in Non-iterative Application of EPANET 2 in Pressure-Dependent Volume-Driven Analysis of Water Distribution Networks

While analysing a real network, the assumption of zero minimum pressure head as the elevation of demand node may lead to unrealistic results as some residual pressure is necessary to derive any outflow at the node. A more realistic minimum pressure head plays an important role for analysis of an existing or proposed network. The present study extends a novel method of pressure-dependent volume driven-analysis by investigating the effects of realistic minimum pressure heads. The novelty of the proposed method is to evaluate the practical impact of the zero minimum pressure head assumption under pressure-deficient condition in water distribution networks considering pipe isolation, fire demand, and altering total reservoir heads. The results obtained from the present method are compared with the results based on the more optimistic traditional assumption of zero minimum residual pressure-head. It is observed that time to fill the storage tanks under both normal and pressure-deficient conditions for non-zero minimum pressure head is higher. All the simulations were performed using graphical user interface of EPANET 2. Thus, the proposed approach can be used readily by researchers and practitioners without requiring any additional computational codes development.

Survival analysis of water distribution network under intermittent water supply conditions

Abstract Intermittent water supply (IWS) is established temporarily or continuously in many water distribution networks (WDNs) worldwide due to prolonged drought, low rainfall periods, water scarcity and high level of leakage. IWS causes several adverse consequences on the network operation, resulting in ineffective supply and demand management. This paper presents a survival analysis of the network elements, including water mains, service connections, and valves using the Kaplan-Meier approach to determine the survival probability and the probability of failure rates of events of interest. The objective is to explore the changes in failure rates of network elements after implementing an IWS scheme. The non-parametric survival method is applied to the large zone (Zone-5) of the WDN in Tehran (Iran) based on the frequency of failures before, during, and after the implementation of an IWS regime. The results show that the probability of failure rates significantly increase after implementing the IWS scheme, and can remain for several years after, even when the network returns to continuous water supply (CWS). The results of this study can assist utility managers to understand the detrimental effects of IWS systems on increasing failure rates.

Vulnerability analysis of water distribution networks to accidental pipe burst

Even the best-maintained water distribution network (WDN) might suffer pipe bursts occasionally, and the utility company must reconstruct the damaged sections of the system. The affected area must be segregated by closing the corresponding isolation valves; as a result, the required amount of drinking water might not be available. This paper explores the behaviour and topology of segments, especially their criticality from the viewpoint of the whole system. A novel, objective, dimensionless, segment-based quantity is proposed to evaluate the vulnerability of both the segments and the whole WDN against a single, incidental pipe break, computed as the product of the probability of failure within the segment and the amount of unserved consumption. 27 comprehensive real-life WDNs have been examined by means of the new metric and with the help of complex network theory, exploiting the concept of the degree distribution and topology-based structural properties (e.g. network diameter, clustering coefficient). It was found that metrics based purely on topology suggest different network behaviour as vulnerability analysis, which also includes the hydraulics. The investigation of the global network vulnerabilities has revealed several critically exposed systems, and the local distributions unveiled new properties of WDNs in the case of a random pipe break.