Reliability Of Water Distribution System Research Articles

Hydraulic and Water Quality Reliability of Water Distribution System under Uncertain Conditions

Reliability assessment plays a significant role in the planning, design, and operation of water distribution systems (WDS). Herein, pressure, flow, chlorine concentration, and water age are simulated by continuity, energy, and transport equations; and hydraulic, water quality, and system reliability assessments are proposed based on a comparison between simulated hydraulic and water quality conditions and the desired service level. Because the independent parameters in hydraulic and water quality simulations cannot be estimated accurately, a hydraulic and water quality reliability assessment based on Monte Carlo simulation was applied to a network under three uncertain levels under steady- and unsteady-states. The effects of uncertain parameters on hydraulic and water quality reliability under steady- and unsteady-states were evaluated and compared to obtain the most significant parameters. The results indicated that the mean hydraulic reliability decreases with an increase in the uncertainty level for various nodes under steady- and unsteady-states, while the regulation is not suitable for water quality reliability. Pipe diameters have the most significant effects on hydraulic reliability under steady-state conditions, and mean hydraulic reliability under unsteady-state conditions. Nodal demand, bulk decay coefficient, and wall decay coefficient have effects on water quality reliability under steady-state conditions, while the roughness coefficient and pipe diameter also have effects on mean water quality reliability under unsteady-state condition. The results obtained can give managers more information about network reliability under uncertain conditions.

Anticipating water distribution service outages from increasing temperatures

With projected temperature increases and extreme events due to climate change for many regions of the world, characterizing the impacts of these emerging hazards on water distribution systems is necessary to identify and prioritize adaptation strategies for ensuring reliability. To aid decision-making, new insights are needed into how water distribution system reliability to climate-driven heat will change, and the proactive maintenance strategies available to combat failures. To this end, we present the model Perses, a framework that joins a water distribution network hydraulic solver with reliability models of physical assets or components to estimate temperature increase-driven failures and resulting service outages in the long term. A theoretical case study is developed using Phoenix, Arizona temperature profiles, a city with extreme temperatures and a rapidly expanding infrastructure. By end-of-century under hotter futures there are projected to be 1%–5% more pump failures, 2%–5% more PVC pipe failures, and 3%–7% more iron pipe failures (RCP 4.5–8.5) than a baseline historical temperature profile. Service outages, which constitute inadequate pressure for domestic and commercial use are projected to increase by 16%–26% above the baseline under maximum temperature conditions. The exceedance of baseline failures, when compounded across a large metro region, reveals potential challenges for budgeting, management, and maintenance. An exploration of the mitigation potential of adaptation strategies shows that expedited repair times are capable of offsetting the additional outages from climate change, but will come with a cost.

Comparison of the Performance of a Surrogate Based Gaussian Process, NSGA2 and PSO Multi-objective Optimization of the Operation and Fuzzy Structural Reliability of Water Distribution System: Case Study for the City of Asmara, Eritrea

Comparison of the Performance of a Surrogate Based Gaussian Process, NSGA2 and PSO Multi-objective Optimization of the Operation and Fuzzy Structural Reliability of Water Distribution System: Case Study for the City of Asmara, Eritrea

RELIABILITY ANALYSIS OF WATER DISTRIBUTION SYSTEMS

Based on node flow analysis the available nodal flows under deficient conditions is presented for determining the reliability of water distribution system (WDS). The reliability is concentration on a node-reliability factor. Volume reliability factor, and network-reliability factor.Even though reliability of WDS depends on several parameters, only variation of consumption in daily, demand excess, and element failure conditions are considered. Computer programs have been written to determine the aforementioned reliability factors. The procedure is described and illustrated through an example.

Evaluation of water quality reliability based on entropy in water distribution system

In this paper, water quality redundancy/reliability was proposed based on information entropy technology including Tsalli entropy and Shannon entropy in water distribution system (WDS), which was applied to 26 WDS with various layouts. The residual chlorine is considered to be representative of water quality parameter, comply with first-order decay model. The method was performed based on EPANET toolkit and MATLAB environment. The results indicated that approach 1 focused on local nodal water quality is more suitable for evaluating water quality reliability, especially for small WDS. The water quality redundancy increased with the loop number for various layouts, and has an exponential relationship with distance-weighted average nodal degree. The water quality redundancy has a linear relationship with the hydraulic redundancy. In addition, the water quality reliability based on Tsalli entropy and Shannon entropy decreased with the value of decay coefficient, which indicated that the water quality redundancy/reliability can be applied to evaluate and compare the reliability of WDS from view of water quality. The proposed evaluation method based on information entropy can help design, analyze, and improve the scenarios in WDS.

Analysis of reliability and belief degree for water distribution system based on fuzzy set theory

ABSTRACT The reliability of water distribution system (WDS) involves imprecise or uncertain parameters. For hydraulic reliability, the uncertain parameters include roughness coefficient, nodal water demand, and the reservoir water level, etc. While water quality reliability is primarily related to chlorine concentrations, with uncertainty parameters including both bulk decay coefficients and wall decay coefficients. The uncertain independent parameters lead to the uncertain results of reliability simulation. As such, fuzzy set theory was proposed to analyze the reliability of WDS and associated belief degree (BD) of calculated reliability. The proposed method was applied to two examples to solve the uncertainty in traditional reliability assessment. The system reliability and BD of WDS were obtained by assumed three uncertainty levels. In addition, the sensitivity analysis of uncertain independent parameters was performed to compare the effects of parameters on simulated reliability and associated BD. The proposed method can help municipalities to make scientific pipe network programming to improve the reliability of WDS.

Assessment of optimal water distribution systems design under steady-state and transient conditions due to pipe roughness uncertainty

This paper presents a methodology to find the optimal design or rehabilitation of water distribution system (WDS) under both steady-state and transient conditions. Then, assessing the obtained optimal solution and studying its stability, reliability, due to uncertainty in pipe roughness coefficients (CHW). The WDS optimization objective is to minimize the rehabilitation cost by installing new pipes parallel to the existing ones achieving all hydraulic constraints. For this purpose, particle swarm optimization (PSO) is used as an optimization tool and Monte Carlo simulation (MCS) is applied to generate multiple realizations of CHW for different coefficient of variation (COVCHW). A comparison between crisp shape and continuous shape (S-shape) fuzzy membership functions is carried out to study the hydraulic availability indices to nodal pressure head values resulted from pipe roughness uncertainty. Both steady-state nodal and system reliabilities are estimated while, only the transient system reliability is calculated for the obtained optimal solution. The proposed methodology is applied on the New York City tunnel network (NYCTN) and the corresponding reliability is analyzed. Results show that as pipe roughness uncertainty increases, WDS reliability decreases.

Discussion of “Graph-Theoretic Surrogate Measure to Analyze Reliability of Water Distribution System Using Bayesian Belief Network–Based Data Fusion Technique” by Ngandu Balekelayi and Solomon Tesfamariam

Discussion of “Graph-Theoretic Surrogate Measure to Analyze Reliability of Water Distribution System Using Bayesian Belief Network–Based Data Fusion Technique” by Ngandu Balekelayi and Solomon Tesfamariam

Closure to “Graph-Theoretic Surrogate Measure to Analyze Reliability of Water Distribution System Using Bayesian Belief Network–Based Data Fusion Technique” by Ngandu Balekelayi and Solomon Tesfamariam

Closure to “Graph-Theoretic Surrogate Measure to Analyze Reliability of Water Distribution System Using Bayesian Belief Network–Based Data Fusion Technique” by Ngandu Balekelayi and Solomon Tesfamariam

How Are Various Surrogate Indicators Consistent with Mechanical Reliability of Water Distribution Systems: From a Perspective of Many-Objective Optimization

Exploring the trade-off between cost and system reliability of water distribution systems (WDSs) has been focused for two decades. Due to the intensive computation associated with the reliability analysis, it is popular in the research community to replace this procedure by using surrogate indicators. However, the discussion on the correlation among different types of such indicators is generally lacking, which implies that a deeper understanding of this aspect is needed. This paper proposes a novel methodology of investigating the relationships among many commonly used surrogate indicators for measuring the mechanical reliability of WDSs. In particular, the optimal design of WDSs is formulated as a many-objective optimization problem, using cost and each surrogate indicator as an individual goal. Two benchmark design problems of different scales and complexities are considered for verifying the proposed method. The well-known multi-objective evolutionary algorithm (MOEA), namely Borg that is suitable for coping with problems involving many objectives, is used to obtain the best approximation to the Pareto-optimal fronts for both cases. Afterward, the one-pipe burst testing is conducted to quantify the correlation between mechanical reliability and surrogate indicators. Results suggest that investigating the correlation of surrogate indicators from the perspective of many-objective optimization provides a direct and efficient way of distinguishing better indicators from worse ones. Resilience-based surrogate indicators and the Redundancy indicator that only depends on nodal pressures are highly related to the mechanical reliability of WDSs. In contrast, entropy-based indicators exhibit poor performance in reflecting the mechanical reliability. These insights contribute to the selection of more appropriate surrogate indicators for the optimal design of WDSs for researchers and practitioners.

A Framework for Improving Reliability of Water Distribution Systems Based on a Segment-Based Minimum Cut-Set Approach

A framework is presented to effectively improve the water distribution system (WDS) reliability. The proposed framework first classifies pipes in a WDS into three reinforcement types through topological analyses and hydraulic simulations over the WDS; type 1: no reinforcement, type 2: increasing pipe durability, and type 3: installing valve(s) at both ends. Then two rules, rules 1 and 2, are implemented, in which rule 1 first reinforces the pipe with the lowest reliability but rule 2 preferentially reduces damage size by pipe failures represented as the expected number of customers out of service (EN). The proposed method was applied to Cherry Hill network, and considerably improved the WDS reliability from 0.137 to 0.483. Both approaches showed notable differences in changes of the EN at each step of reinforcement, where rule 2 showed a better capability to reduce the EN and detect vulnerable areas in the WDS than rule 1. In addition, a practical approach, maximizing valve installations and minimizing pipe replacements according to the reinforcement types in the system, provided an improved WDS reliability (0.423) close to that of the rule-based approach (0.483) using only 21% of the construction cost by the rule-based approach. The proposed framework can be guidelines for improving the WDS reliability under restricted budget and site conditions.

Graph-Theoretic Surrogate Measure to Analyze Reliability of Water Distribution System Using Bayesian Belief Network–Based Data Fusion Technique

AbstractReliability assessment is an integral component of the decision-making process in the planning, design, and operations of water distribution networks (WDNs). Two different approaches are us...

Water quality reliability based on information entropy technology in water distribution system

Reliability of Water Distribution System (WDS) had been widely studied from mechanical and hydraulic aspects for a long time. Compared with them, water quality reliability (WQR) of WDS was not widely-presented by now. In this paper, WQR model of WDS based on entropy technology was proposed and applied to two typical water distribution systems. The results obtained showed that the water quality reliability had relationship with water sources, which was also important for hydraulic reliability of WDS. As a result, the presented model was suitable for assessing the water quality reliability of WDS.

Water Distribution Systems Reliability: A Review of Research Literature

AbstractEvery water distribution system (WDS) fails partially or completely at some point or points during its lifetime. Measurement of reliability for a WDS under various failure conditions is necessary. Numerous techniques have been developed for estimating WDS reliability. This study provides an in-depth review of the relevant research literature (subsequently referred to simply as “literature”) in the context of mathematical methods for measuring WDS reliability. It was found that the literature is vague as types of failure (mechanical, hydraulic, and water quality failure) and techniques of reliability analysis are mixed together inappropriately. This research organized and classified the available techniques into three major categories and discussed which technique should be used depending upon the type of a failure. A particular state of failure could have several simultaneous unfavorable impacts on a WDS operation. Deep insight into the relevant literature revealed that simultaneous multiaspect/st...

Linear Model for Estimating Water Distribution System Reliability

AbstractThe water distribution system (WDS) reliability is the ability of a network to provide the required quantity of water to customers under uncertain system conditions. In this study, eight surrogate measures of WDS reliability were investigated: Two hydraulic reliability measures, two robustness measures, single failure reliability (SFRel) with three valve installation levels, and seismic reliability (SeisRel). The eight reliability measures were calculated for 16 study networks of various sizes (i.e., in terms of the number of nodes and links), numbers of sources, layouts, demand distributions, and topographies. The network characteristics (e.g., structural redundancy and overall pipe sizes) were quantified by using system characteristic indicators (SCI), and their correlations with the eight suggested reliability measures were analyzed. The following SCIs were considered: The average node degree, meshedness coefficient, total system demand, total system demand per source, length-weighted average p...

Multistate Reliability of Water-Distribution Systems: Comparison of Surrogate Measures

AbstractReliability of a water-distribution system (WDS) can address mechanical, hydraulics, and water quality failure in the system. The research reported in this paper focused on mechanical reliability (subsequently referred to simply as reliability) assessment of a WDS. Existing techniques are restricted to lower states of reliability (one pipe failure at a time) and very little attention has been paid to higher states (simultaneous failure of several pipes). This is due to large computational workload associated with higher-states reliability assessment. Studying various reliability measures, the research reported in this paper revealed statistical flow entropy had stronger correlation with higher states of reliability and was a better surrogate measure. A multicriteria decision analysis (MCDA) was applied to rank a set of WDS layouts (alternatives) using various states of reliabilities (criteria). The MCDA considered the relative importance of each state of reliability in the process of finding the m...

Water distribution system reliability under simultaneous multicomponent failure scenario

Water distribution systems (WDSs) face numerous challenges in providing service to their customers. An especially difficult challenge occurs when several pipes in the system fail simultaneously. Simultaneous failure is more likely to occur in older networks or systems located in harsh climatic conditions. Previous studies have focused on WDS reliability when pipes fail individually. The current research proposes a technique to determine the reliability of a WDS experiencing different degrees of simultaneous pipe failure and to assess errors in reliability that occur when an inappropriate level of simultaneous failure is assumed. The model was applied to two case studies including a hypothetical small system and an actual WDS. Comparing the various states of reliability provided valuable information about system sensitivity to simultaneous multipipe failures. Results demonstrated that a system may be able to achieve a higher level of reliability if more realistic expectations of simultaneous failure are assumed.

A Bayesian vulnerability assessment tool for drinking water mains under extreme events

Drinking water security is a life safety issue as an adequate supply of safe water is essential for economic, social and sanitary reasons. Damage to any element of a water system, as well as corruption of resource quality, may have significant effects on the population it serves and on all other dependent resources and activities. As well as an analysis of the reliability of water distribution systems in ordinary conditions, it is also crucial to assess system vulnerability in the event of natural disasters and of malicious or accidental anthropogenic acts. The present work summarizes the initial results of research activities that are underway with the intention of developing a vulnerability assessment methodology for drinking water infrastructures subject to hazardous events. The main aim of the work was therefore to provide decision makers with an effective operational tool which could support them mainly to increase risk awareness and preparedness and, possibly, to ease emergency management. The proposed tool is based on Bayesian Belief Networks (BBN), a probabilistic methodology which has demonstrated outstanding potential to integrate a range of sources of knowledge, a great flexibility and the ability to handle in a mathematically sound way uncertainty due to data scarcity and/or limited knowledge of the system to be managed. The tool was implemented to analyze the vulnerability of two of the most important water supply systems in the Apulia region (southern Italy) which have been damaged in the past by natural hazards. As well as being useful for testing and improving the predictive capabilities of the methodology and for possibly modifying its structure and features, the case studies have also helped to underline its strengths and weaknesses. Particularly, the experiences carried out demonstrated how the use of BBN was consistent with the lack of data reliability, quality and accessibility which are typical of complex infrastructures, such as the water distribution networks. The potential applications and future developments of the proposed tool have been also discussed accordingly.

Performance and Reliability Analysis of Water Distribution Systems under Cascading Failures and the Identification of Crucial Pipes

As a mean of supplying water, Water distribution system (WDS) is one of the most important complex infrastructures. The stability and reliability are critical for urban activities. WDSs can be characterized by networks of multiple nodes (e.g. reservoirs and junctions) and interconnected by physical links (e.g. pipes). Instead of analyzing highest failure rate or highest betweenness, reliability of WDS is evaluated by introducing hydraulic analysis and cascading failures (conductive failure pattern) from complex network. The crucial pipes are identified eventually. The proposed methodology is illustrated by an example. The results show that the demand multiplier has a great influence on the peak of reliability and the persistent time of the cascading failures in its propagation in WDS. The time period when the system has the highest reliability is when the demand multiplier is less than 1. There is a threshold of tolerance parameter exists. When the tolerance parameter is less than the threshold, the time period with the highest system reliability does not meet minimum value of demand multiplier. The results indicate that the system reliability should be evaluated with the properties of WDS and the characteristics of cascading failures, so as to improve its ability of resisting disasters.

Simultaneous Multi-pipe Failure Impact on Reliability of Water Distribution Systems

Abstract Hydraulic reliability assessment of a water distribution system (WDS) can be performed at different states considering various combinations of pipe failures. Current reliability techniques are mostly restricted to lower sates of reliability considering just one pipe failure at a time. In this study, multi-criteria decision analysis (MCDA) approach is applied to rank a set of distribution layouts (alternatives) using various states of reliabilities (criteria). Results show that multi-state reliability assessment (MSRA) of a WDS may lead to completely different and more comprehensive results since considering various states of reliability at the same time.