Reliability Of Water Distribution Networks Research Articles

Service Pressure and Energy Consumption Mitigation-Oriented Partitioning of Closed Water Distribution Networks

This paper presents the partitioning of the closed water distribution network (WDN) serving the city of Pavia, Italy. As a thus far poorly explored aspect in the scientific literature, clustering for the definition of size and extension of district metered areas (DMAs) and of inter-DMA boundary pipes is performed by ensuring that the DMAs respect the altimetric areas of the WDN by leaning on a modified formulation of modularity. To define the boundary pipes to be closed or alternatively fitted with a flow meter for the monitoring of DMA consumption, the dividing is performed with an innovative heuristic algorithm. This technique operates by sequentially implementing the boundary closures that do not cause significant head losses, to obtain an approximation of the Pareto front in the trade-off between number of flow meters installed and WDN reliability. In the last part of the work, the pumps present in the network are assumed to be equipped with the variable speed drive, and their hourly settings are optimized to regulate service pressure. Overall, WDN partitioning and pump setting optimization are proven to mitigate the service pressure and energy consumption of the WDN, offering evident and attractive benefits up to about 50% for water utilities.

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.

Advances in Assessing the Reliability of Water Distribution Networks: A Bibliometric Analysis and Scoping Review

The reliability of Water Distribution Networks (WDNs) is a critical topic that has been explored by many researchers over the last few decades. Nevertheless, this research domain has gained momentum in the last decade. WDN reliability was addressed in the literature using different approaches and techniques. This study presents a bibliometric analysis and scoping review of the progress and gaps in research on WDN reliability. The analysis was performed on a total of 347 articles from 2000 to 2022, which were retrieved from the SCOPUS database. The bibliometric analysis identified trends and gaps by focusing on articles output, citation network of articles, co-authorship and collaboration analysis, co-citation, and clustering analysis. In addition, coupling keywords analysis with thematic maps analysis helped identify basic, niche, emerging, and declining research themes in the field of WDN reliability. Three major research themes were found: WDN optimization, reliability assessment, and consideration of GHG emissions and energy-cost for WDN expansion. Reliability surrogate measures (RSMs) were found to be one of the most widely researched topics in this field. Performance assessment of various RSMs, as well as the consideration of energy and cost for WDN design and expansion stood out as the emerging trends for future research in the field of WDN reliability.

Analysis of the isolation valve system in water distribution networks using the segment graph

The mechanical reliability of Water Distribution Networks (WDNs) is a relevant technical and scientific issue. During planned maintenance or unplanned interruptions, the affected area must be isolated by valves shutdown. This operation involves the alteration of the network structure, i.e., the domain of the hydraulic system, and for this reason the isolation valve system plays a central role. Some studies started to consider the presence of the isolation valve system in WDNs reliability analysis.Accordingly, this work uses the Complex Network Theory to analyse the isolation valve system performance and to assess the importance of the segments generated by valves shutdown. Differently from the classic complex network theory approach, in this work the recently proposed WDN-relevance-based betweenness centrality is applied to the segment graph to introduce information about the relevance of the different elements into the network, considering geometric and hydraulic parameters, such as length, demand, risk of disconnection, etc. The proposed strategy also suggests an improvement in the representation of the segment graph with respect to the presence of parallel edges.The strategy is presented using a small network, while it is demonstrated and discussed using a real WDN. The results indicate that the WDN-relevance-based betweenness centrality allows to effectively assess the importance of the segments generated by valves shutdowns, also providing indications to improve the isolation valve system design.

Stochastic long-term reliability of water distribution networks using Monte Carlo simulation

ABSTRACT In this paper, a new method is developed to consider the effect of pipe roughness, diameter and nodal demand uncertainty on the overall reliability of the Water Distribution networks (WDNs) throughout the day as well as the planning horizon. For this purpose, probabilistic series for each of the mentioned parameters is generated by Monte Carlo Simulation (MCS). Network Pressure Reliability Index (NPRI) is then used to evaluate the overall reliability of the system. The study is performed on the benchmark Two-loop sample network and a real-world one. The comparison of deterministic and stochastic results reveal that the stochastic method tends to capture subtleties missed by deterministic method such as probability of failing the reliability in various locations at the same time. Also, the stochastic method seems to have an undoubted advantage in prediction of undesirable results prior to deterministic method, making it an essential component in long-term planning.

Reliability assessment of water distribution network using specific forms of state space models

ABSTRACT This article introduces methods used for the assessment and prediction of water distribution network (WDN) reliability. A failure rate expressed as the number of failures per operating day is considered to be the basic measure of the achieved WDN reliability level. The proposed method is based on the assumption that information about WDN failures is available in the form of long-term time series. The authors propose a mathematical model using specific forms of state space models which takes into account a seasonal effect and an intervention variable. The proposed model enables us to identify and assess both long-term trends in WDN reliability evolution and short-term reliability changes related to seasonal effects and also to predict the future development of WDN reliability. The practical applicability of the proposed method is demonstrated by assessing the information set based on long-term observations of the selected WDN failures.

A New Method for Optimization of Water Distribution Networks While Considering Accidents

Optimization of water distribution networks can effectively reduce their annual cost, which includes the average investment for each year the operational costs and depreciation costs. However, the existing optimization models rarely directly consider the basic flow of each node in case of accidents, such as pipe bursts. Therefore, it is necessary to check the flow requirements under accident conditions. In order to deal with these drawbacks, two optimization models are established considering accident conditions: a single-objective optimization model considering annual cost as an economic objective, and a multi-objective optimization model with a reliability objective defined by the surplus water head. These models are solved based on the genetic algorithm, non-dominated sorting genetic algorithm-II algorithm and Levenberg-Marquardt iterative method. Applying two cases of a single pump station and a multi pump water station water supply, it is shown that the annual cost when considering the accident conditions is higher than that without considering the accident conditions. Moreover, the annual cost obtained with the multi-objective optimization model is slightly higher than that obtained with the single-objective optimization model. The cost is higher because the former model reduces the average surplus water head, which can improve the water distribution network reliability. Therefore, the model and optimization algorithm proposed in this paper can provide a general and fast optimization tool for water distribution network optimization.

Assessing the Performance of Surrogate Measures for Water Distribution Network Reliability

AbstractThis paper investigates the use of surrogate measures as potential substitutes for reliability in multiobjective design of water distribution networks (WDNs). Assessing WDN reliability with...

Seismic reliability analysis of water distribution networks on the basis of the probability density evolution method

In this study, a new approach for assessing the seismic functional reliability of water distribution networks is presented on the basis of the probability density evolution method. The original contribution of this paper is to build a new framework for the reliability analysis of water distribution networks on the basis of the physical mechanism of water distribution networks subjected to earthquakes. Firstly, a finite element model is established to capture the seismic response of the entire buried pipe networks. Then the nodal head of water distribution networks is derived through hydraulic analysis of water distribution networks with leakages. Secondly, owing to the randomness of ground motions, the probability density functions of the nodal heads of water distribution networks are obtained on the basis of the probability density evolution method. Thirdly, the seismic functional reliability of water distribution networks is evaluated considering the demand heads of nodes. When the nodal head is larger than the predetermined water head, the node is reliable while when the nodal head is smaller than the predetermined water head, the node is not reliable. Two examples, namely, a virtual and an actual water distribution networks, are examined in detail to investigate the feasibility of the proposed method. Results show that the proposed method effectively evaluates the seismic functional reliability of water distribution networks.

Reliability of water distribution networks subjected to seismic hazard: Application of an improved entropy function

This study aims at improving an entropy-based measure considering both total and partial failure, for assessing the reliability and redundancy of Water Distribution Networks (WDNs) during seismic events, which was not explicitly addressed in previous literature. In order to capture the effects of connectivity order of the network nodes as well as the seismic hazard of the site in reliability studies, new entropy calculation method is proposed using hazard information of seismic regions and fragility curve of pipelines. Subsequently, the effect of failure of each pipe due to a seismic event, which results in reducing the serviceability and reliability of a WDN, is investigated using the proposed entropy calculation. The results indicate that the proposed entropy function is capable of estimating the reliability trend of WDNs considering different failure patterns caused by different hazard levels. The proposed method enables the engineers and practitioners to find a proper optimum design approach for the water supply network and plays an important role in assessing the performance of WDNs and mitigating the chance of total failure of WDN in hazardous zones.

Flow-Uniformity Index for Reliable-Based Optimal Design of Water-Distribution Networks

AbstractThe reliability of water distribution network (WDN) designs for satisfying water demands under normal and abnormal operating conditions, including during pipe bursts and as systems age, is ...

Pressure Management of Large-Scale Water Distribution Network Using Optimal Location and Valve Setting

This paper presents a new method to optimize the location and setting of Pressure Reducing Valves (PRVs) for adjusting the nodal pressure at different hours of a day by maximizing the reliability of Water Distribution Network (WDN). The methodology is based on Particle Swarm Optimization (PSO) algorithm that is written in the MATLAB code by linking to a hydraulic model of the WDN which is implemented in the EPANET. For verifying the proposed method, a sample network and a real large-scale WDN are applied. The results indicate that the determination of the optimal location and setting of PRVs in the WDN are effective in adjusting nodal pressures and reducing leakage rates. Comparison of the results for the cases with optimized PRVs and without PRVs in a real WDN showed that the average leakage rate is decreased about 15.0% and the average reliability index is increased about 24.8%.

Water Distribution Network Reliability Assessment and Isolation Valve System

Mechanical reliability analysis of water distribution networks (WDNs) refers to the assessment to provide correct service to customers under abnormal functioning conditions due to system component failures. Mechanical reliability depends on the isolation valve system (IVS) effectiveness in isolating a network segment and on the failure probability. The main aim of this work was the formal development of reliability indicators considering pressure-driven analysis (PDA) for customer demand and topological changes. Three factors influencing reliability were identified: (1) the hydraulic behavior of the still-connected network; (2) the topological performance of the IVS; and (3) the topological performance of the IVS with respect to unintended isolation. The reliability performance assessment of the network over time depends on the hydraulic capacity of the WDN under abnormal functioning conditions and on two IVS performance topological indicators of the risk of disconnection and unintended isolations. The hydraulic capacity was computed using PDA, whereas the topological risks were computed considering the unsupplied demand in the isolated segment and the normalized failure probability, i.e., the probability of a segment disconnection for an assumed failure occurrence in the network. The development of a modularity index for an IVS was achieved in a consistent framework and the integrated design of an IVS and district metering areas was introduced. The framework allows the analysis of the isolation valve failure. A real Apulian WDN was used to discuss and demonstrate the theoretical findings.

Reliability of Water Distribution Networks

Reliability of Water Distribution Networks

A Dynamic Adaptive Approach for Water Distribution Network Design

In the face of a highly uncertain future, there is a need for water utilities to develop structured approaches for the long-term strategic design of water distribution networks (WDNs). A new conceptual framework for developing an integrative approach based on a multicriteria decision analysis (MCDA), embracing an optimization model to size flexible alternatives, is proposed. The flexible solutions are evaluated through MCDA for all the criteria (investment costs, carbon emissions, resilience, and reliability of WDNs) across all the scenarios generated for the sake of robustness and will help to adapt WDNs to changing conditions over a long planning horizon, divided into phases. The alternatives are ranked through two different MCDA methods, Preference Ranking Organization METHod for Enrichment of Evaluations (PROMETHEE) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), so that decision makers will have more comprehensive information for analyzing highly ranked design solutions and after the first phase, solutions for the other phases can be reassessed by the same dynamic adaptive framework.

Optimal Design of Water Distribution Networks with Incorporation of Uncertainties and Energy Nexus

The reliability of water distribution networks is susceptible to large impacts resulting from uncertainties. Several factors may contribute to such uncertainties. These include nodal demands, reservoir/tank levels, and availability of system components. Additional sources of uncertainties arise when water-energy nexus is considered. For instance, when water desalination systems that are coupled with power plants are incorporated in the water distribution networks, uncertainties in energy demand influence the design of the water network system. In this work, a multi-objective optimization framework is developed for the design of water networks that involve dual-purpose power plants for simultaneous water desalination and power generation. The multi-objective model accounts for sustainability goals through environmental, economic, and societal metrics such as greenhouse gas emissions, net profit, and number of jobs created, respectively. Fossil fuels, as well as renewable biofuels and solar power, are considered as candidate sources of energy. Water resources include multiple systems such as dams, lakes, rivers, aquifers, and artificial storage lakes. Demands from agricultural, industrial as well as domestic needs in the region are considered. In order to incorporate uncertainty in the proposed approach, a stochastic optimization model is formulated with a probabilistic objective function and constraints. The network has multiple sources as well as demands with varied distributions. In order to find an overall distribution for probability density estimation, a decomposition scheme is applied where each scenario is solved separately as a sub-problem. The solution from sub-problem is used to find the probability using kernel density estimator. The modified model equations lead to a stochastic MINLP problem. The proposed framework and optimization formulations are applied to a case study in the Mexican state of Sonora. From the demand and natural resource distribution, 12 scenarios have been identified and the model is weighted by their probability of occurrence. The results are compared with the deterministic solution to obtain the cost associated with uncertainty.

Upgrading the Reliability of Water Distribution Networks through Optimal Use of Pressure-Reducing Valves

AbstractHigh pressure in water distribution networks may lead to more leakages, bursts, and excessive consumption. Therefore, an effective strategy to improve the reliability of the network is pres...

New indices for reliability assessment of water distribution networks

This paper presents new indices to evaluate the reliability of water distribution networks (WDNs) usable in the design, planning and management of these networks. Since the pressure-driven analysis (PDA) of WDNs produces more accurate results than the demand-driven analysis, the new indices are proposed based on the PDA. In the proposed measures, nodal pressures, nodal available discharges and the energy loss per unit length of pipes are considered as the main factors influencing the reliability of WDNs. The introduced network reliability index is a combination of two indices named total nodal reliability and total pipe reliability. These indices are equal to the weighted average of all of the nodal and pipe reliabilities, respectively. A sample network is used to evaluate the new proposed index and some of the available indices and to compare their efficiencies in assessing the reliability of WDNs. The results show that the new proposed index is more efficient and outperforms the others. The introduced index is normalized and is independent of the WDN size. This index considers the qualitative aspects of WDNs besides the hydraulic aspects in evaluating reliability.

Water distribution network robust design based on energy surplus index maximization

The aim of this paper is to show that energy surplus indices, such as resilience index, besides providing a very good indirect measure of water distribution network reliability, also represent a valuable and effective indicator of network robustness under alternative network scenarios. It can thus be profitably used for network design under conditions of uncertain future demands. The methodology adopted consisted of: (a) multi-objective design optimization performed in order to minimize construction costs while maximizing the resilience index; and (b) retrospective performance assessment of the alternative solutions of the Pareto front obtained, under demand conditions far from those assumed during the design phase. Two case studies of different topological complexity were considered. Results showed that the resilience index, which is one of the most effective indirect indices of reliability, represents a very good measure of robustness as well.

Seismic functional reliability analysis of water distribution networks

Due to the huge destructive power of strong earthquakes, many breaks appear on water pipelines after such events. As a result, water leaks from these breaks, causing function loss of water distribution networks (WDNs). In order to evaluate the seismic performance of WDNs, these leaks cannot be ignored. In this paper, by adding a leakage model to the hydraulic equation of WDNs in a daily operation state, a new hydraulic equation is established to describe WDNs after the occurrence of earthquakes. As it is a stochastic equation, a random perturbation method is used to solve the equation and give the mean, standard deviation and skewness of the nodal head. In the meantime, a performance function is established to evaluate the reliability of WDNs. Three reliability analysis methods, a mean first-order second-moment method and two third-moment methods, are used to give the seismic functional reliability of WDNs. Meanwhile, two networks, a small WDN and an actual WDN which suffered serious damages during the Wenchuan Earthquake, 2008, are studied to compare the efficiency and precision of the three reliability methods.