Urban Water Distribution Networks Research Articles

Urban Water Management at the Time of Natural Disaster

Since natural disasters occur, facilities which are related to this vital element are underground so, it is difficult to rapid access to correct, accurate and reliable information of urban water distribution network. Therefore, this article has done operationally in Boukan city which is located in Western Azarbaijan of Iran and it tries to represent by using rules and data of construction management, urban designing and capabilities of Geographical Information system (GIS) in urban water management at the time of natural disasters. Structure of this article is like that in first we established a comprehensive data base related to water utilities by collecting, entering, saving and data management, then by modeling water utilities we had practically considered its

Study on Safety Evaluation Method for Water Distribution Networks Based on LS-SVM

To evaluate the security of urban water distribution network, one model based on LS-SVM was put forth. On the basis of summary and analysis of influential factors for urban water distribution network security, a set of indexes used in the evaluation model above was constructed. The nonlinear mapping between the water distribution networks security classification and its conditions were learned from the finite samples and a water distribution network example was simulated using this model. In addition, the BP ANN model was used to simulate the same example. Through the analysis of the result of the actual security level, the security level acquired by the LS-SVM model and BP ANN model, it may be found that the result acquired by the LS-SVM model has high accuracy, and may used in actual engineering.

Field testing of an optimal sensor placement methodology for event detection in an urban water distribution network

This paper presents a method to identify ‘optimal’ locations of pressure sensor instruments for the detection of leak/burst events and the results of a set of field trials conducted to evaluate the approach. The identification method is based on complete enumeration studies using hydraulic model simulations of a wide range of burst events and evaluating the response to each event at all possible monitoring points. The field trials simulated leak/burst events through the opening of fire hydrants within a selected District Metered Area (DMA), five different hydrants were opened systematically in the DMA to simulate different leak/burst events. By installing pressure instrumentation at different locations in the DMA, an understanding of how accurately the model methodology can determine sensitivity of instrument location can be obtained. Prior to and during the hydrant openings pressure data was collected at eight different instrument locations within the DMA. These pressure instruments were installed to cover different model predicted sensitivities and to provide good spatial coverage. The results show that pressure instrumentation location is crucial to sensitivity and that the modelling methodology is able to predict instrument location sensitivity to leak/burst events and thus offer an improvement over current industry practice for instrument deployment. It should be noted that this field application made use of current UK standard models, with no additional calibration or updating.

Results of an urban water distribution network performance evaluation attempt in Greece

The need for efficient water resources management is currently more pressing than ever, considering population growth and increased reliability requirements, under climate change conditions. On average, one-third of the total water abstracted for urban uses is being lost due to leaks and breaks occurring in water distribution networks. This means that significant amounts of water and revenues are being lost, forcing water utilities to consider developing effective water loss and Non-Revenue Water reduction strategies. Additionally, all water utilities operating in EU countries should, by the end of 2010, develop and implement appropriate water pricing policies that will guarantee the recovery of the full cost of the water being used. This strict obligation makes the reduction of water losses an even more urgent goal that the water utilities have to achieve. The first step towards all the above-mentioned goals is to safely evaluate the performance level of the water network. Thus, the IWA Task Forces on Water Losses and Performance Indicators (PIs) developed specific tools (e.g., the standard international water balance and various PIs), to help water utilities use a common language that will assist know-how and experience exchange through an effective benchmarking process. The paper presents the results of using the above-mentioned IWA tools, in the case of the Larisa city water distribution network in Greece. This is the first time that such an attempt has taken place in Greece. During this process, the problems faced and the ways to tackle them are analyzed, focusing on the role of key factors that had to do with local conditions. Larisa's results are compared to data available from similar cases. Sensitivity analysis was used to check the impact of the variables' uncertainty to the results. Finally, water loss reduction measures are proposed towards an effective pressure management strategy and a proactive pipe maintenance policy based on safely estimating the pipes' optimum replacement time.

Water Network Assessment and Reliability Analysis by Use of Survival Analysis

A holistic and sustainable strategy for the management of urban water distribution networks should be composed of two equally important pillars: (1) efficient methods for monitoring, repairing or replacing aging infrastructure, and (2) effective tools for modelling the deterioration in the network and for proactively assessing the risk of failure of its components so as to devise preventive measures for avoiding such failures. The paper presents a framework for devising such a proactive risk-based integrity-monitoring strategy for the management of urban water distribution networks. The framework presented is based on a combination of artificial neural network, parametric and nonparametric survival analysis and it is utilized in the estimation of time-to-failure metrics for pipe networks.

Locating leak detecting sensors in a water distribution network by solving prize-collecting Steiner arborescence problems

We consider the problem of optimizing a novel acoustic leakage detection system for urban water distribution networks. The system is composed of a number of detectors and transponders to be placed in a choice of hydrants such as to provide a desired coverage under given budget restrictions. The problem is modeled as a particular Prize-Collecting Steiner Arborescence Problem. We present a branch-and-cut-and-bound approach taking advantage of the special structure at hand which performs well when compared to other approaches. Furthermore, using a suitable stopping criterion, we obtain approximations of provably excellent quality (in most cases actually optimal solutions). The test bed includes the real water distribution network from the Lausanne region, as well as carefully randomly generated realistic instances.

Proactive Risk-Based Integrity Assessment of Water Distribution Networks

Sustainable management of urban water distribution networks should include not only new methods for monitoring, repairing or replacing aging infrastructure, but also (and more importantly) expanded methods for modelling deteriorating infrastructure, for pro-actively assessing the risk of failure and for devising replace or repair strategies. The study presented herein describes a framework for proactive risk-based integrity monitoring of urban water distribution networks and the results obtained from a case-study based on a 5-year data sample. A combination of artificial neural network and statistical modelling techniques stemming from parametric and nonparametric survival analysis (Kaplan–Meier survival curves with Epanechnikov’s kernel) are utilized in the investigation of identified risk factors and for estimation of the forecasted time to failure metric. The data is stratified for different pipe groups for a more targeted analysis.

Parameter Estimation in Water Distribution Networks

Estimation of pipe roughness coefficients is an important task to be carried out before any water distribution network model is used for online applications such as monitoring and control. In this study, a combined state and parameter estimation model for water distribution networks is presented. Typically, estimation of roughness coefficient for each individual pipe is not possible due to non-availability of sufficient number of measurements. In order to address this problem, a formal procedure based on K-means clustering algorithm is proposed for grouping the pipes which are likely to have the same roughness characteristics. Also, graph-theoretic concepts are used to reduce the dimensionality of the problem and thereby achieve significant computational efficiency. The performance of the proposed model is demonstrated on a realistic urban water distribution network.

A Neurofuzzy Decision Framework for the Management of Water Distribution Networks

Among the most important components of sustainable management strategies for water distribution networks is the ability to integrate risk analysis and asset management decision-support systems (DSS), as well as the ability to incorporate in the analysis financial and socio-political parameters that are associated with the networks in study. Presented herein is a neurofuzzy decision-support system for the performance of multi-factored risk-of-failure analysis and pipe asset management, as applied to urban water distribution networks. The study is based on two datasets (one from New York City and the other from the city of Limassol, Cyprus), analytical and numerical methods, and artificial intelligence techniques (artificial neural networks and fuzzy logic) that capture the underlying knowledge and transform the patterns of the network’s behaviour into a knowledge-repository and a DSS.

Risk-based asset management of water piping networks using neurofuzzy systems

The efficient and organized management of public utility networks is of paramount importance to a network’s viability and reliable functioning. One of the key components of a suitable network management strategy is the utilization of integrated risk analysis and asset management decision-support systems (DSS) that incorporate both the scientific aspects of risk-of-failure analysis for the network components but also the financial and socio-political parameters that are associated with the networks in study. The study reported on presents a neurofuzzy decision-support system for performing multi-factored risk-of-failure analysis and asset management related to urban water distribution networks. The study is based on two datasets (one from New York City and the other from the city of Limassol, Cyprus), analytical and numerical methods, and artificial intelligence techniques (artificial neural networks and fuzzy logic) that capture the underlying knowledge and transform the patterns of the network’s behavior into a knowledge-repository and a DSS. Among the findings reported on, is a methodology to assess the risk of failure in a network, the factors affecting the reliability of pipe segments, and a neurofuzzy approach to breakage-data analysis, stratification and maintenance prioritization. Pipe-breakage history, pipe material, pipe age, and pipe diameter are shown to be significant risk factors in urban water distribution networks.

State Estimation in Water Distribution Networks Using Graph-Theoretic Reduction Strategy

Steady state analysis of flows and pressures in a water distribution network is a major concern for hydraulic engineers involved in the monitoring and control of water distribution systems. Most of the hydraulic network solution strategies currently available are meant for obtaining flows/pressures given a minimum number of measurements. If more measurements than the minimum required are available, then the redundant measurements can be exploited to obtain a better estimate of the state of the network, taking into account noise in these measurements. In this paper, a state estimation technique for well instrumented water distribution networks is described. The proposed method uses graph-theoretic concepts to reduce the dimensionality of the problem and thereby achieves significant computational efficiency. Applicability of the proposed state estimation procedure is demonstrated on realistic urban water distribution networks. It is also shown that the proposed method can be used for state estimation even w...

Seismic reliability analysis of urban water distribution network

An approach to analyze the seismic reliability of water distribution networks by combining a hydraulic analysis with a first-order reliability method (FORM), is proposed in this paper. The hydraulic analysis method for normal conditions is modified to accommodate the special conditions necessary to perform a seismic hydraulic analysis. In order to calculate the leakage area and leaking flow of the pipelines in the hydraulic analysis method, a new leakage model established from the seismic response analysis of buried pipelines is presented. To validate the proposed approach, a network with 17 nodes and 24 pipelines is investigated in detail. The approach is also applied to an actual project consisting of 463 nodes and 767 pipelines. The results show that the proposed approach achieves satisfactory results in analyzing the seismic reliability of large-scale water distribution networks.

Evolving sustainable water networks

The need for efficient pipe networks for urban water supply and drainage is introduced and discussed in the context of global sustainable development. The role of computer based analysis and design tools in the planning and operation of such systems is described, with the way in which these tools can help to minimize use of resources, energy and water losses being explained. In particular, numerical techniques such as Genetic Algorithms, which are based on the principles of natural evolution, are found to be particularly effective in dealing with the large, complex systems that typify urban water distribution networks. These evolutionary techniques are introduced and discussed, and several applications of the techniques to the development of efficient water systems are described. A case study on the use of these techniques in the calibration of an accurate mathematical model of an urban water distribution system is included.

A Neural Network Approach to Simplify Mathematical Models of Urban Water Distribution Networks

Computer-based operational control strategies in water industry require effective and accurate mathematical models of water distribution networks. The model usually consists of a set of nonlinear differential equations. The need for model simplification arises from the fact, that the network model must be simulated many times during optimization and only a very limited subset of variables is usually utilized by a cost function. In the paper a neural network approach to simplification of mathematical models of water distribution networks is discussed. As a case study, a comparison of dynamic behaviour of selected variables calculated by the full mathematical model of a water distribution network and their approximation by a neural network has been presented.

Reply: An analysis of pipe breakage in urban water distribution networks

Reply: An analysis of pipe breakage in urban water distribution networks

Discussion: An analysis of pipe breakage in urban water distribution networks

Discussion: An analysis of pipe breakage in urban water distribution networks

An analysis of pipe breakage in urban water distribution networks

The rates of pipe breakage with increasing pipe diameter and times are investigated. Failure rates for cast-iron pipe are found to decrease with increasing diameter. Changes in pipe failure rates for the various modes of failures are examined in detail. Asbestos-cement and cast-iron pipe overall failure rates are found to increase with time, but for different reasons. Analysis of the modes of failure shows that joint failure is predominant for cast-iron pipe systems with bolted and universal joints whereas the predominant mode of failure for asbestos-cement pipe systems is circumferential cracking. Key words: asbestos cement, cast iron, cracking, diameter, failure rate, joint, regression analysis.