Case-based reasoning to support decision making for managing drinking water quality events in distribution systems

In order to better leverage past experience of water quality incidents, and to tap into the unique incident database currently being maintained and required by regulatory authorities, a data mining approach is herein proposed. The quality of drinking water is paramount to protecting public health. However water quality failures do occur, with some of the hardest to understand and manage occurring within distribution systems. In the UK, a regulatory process is applied in which water service providers must report on significant water quality incidents, their causes, actions and outcomes. These reports form a valuable resource that can be explored for improved understanding, to help with future incident management and evaluate potential solutions. Case-based reasoning is a knowledge-based problem-solving technique that relies on the reuse of past experience. The WaterQualityCBR software system presented here was developed as such a decision support tool to more effectively manage water quality in distribution systems.     

Pressure as a predictor of occurrence of pipe breaks in water distribution networks

Sudden bursts in water distribution networks may lead to costly consequences. As pressure is one of the causes of such events, pressure management could reduce the probability of failure. In this work, a methodology is proposed to analyse the relationship between pipe breaks and water pressure by means of pressure-related indicators. The objective is to identify the most influential indicators for the probability of occurrence of pipe breaks. The methodology compares the cumulative distribution function (CDF) conditioned to breaks and 100 random sets of the same size sampled from the CDF of the indicator. The most influential indicators are related to the greatest number of rejected cases of the Kolmogorov-Smirnov test. Moment indicators and their calculation period emerge from sensitivity analyses. The methodology is applied to six sectors of Madrid (Spain) while two sectors are used for validation. Results show that the pressure range is the best indicator of breaks.     

Accurate water demand spatial allocation for water networks modelling using a new approach

The paper presents an alternative approach regarding the spatial allocation of the actual water demand (at node level) when developing a pipe network's hydraulic simulation model. The process takes into account the respective demand patterns of the various types of water users, considering the water being lost through leaks/breaks occurring, as a competitive use. This new method accurately approximates the demand allocation of a network when there is no GIS data, thus having a significant impact on its cost effectiveness. Kos Town (Greece) water pipe network is used as the case study to demonstrate the entire process and the problems encountered. Finally, to prove its effectiveness the results of the new method were compared to MW-Voronoi diagram method's results and to field measurements.     

Pipe failure predictions in drinking water systems using satellite observations

Soil deformation is believed to play a crucial role in the onset of failures in the underground infrastructure. This article describes a method to generate a replacement-prioritisation map for underground drinking water pipe networks using ground movement data. A segment of the distribution network of a Dutch drinking water company was selected as the study area. Failure registration data comprising 868 failures registered over 40 months and geographical network data were obtained from the water utility. Ground movement was estimated using radar satellite data. Two types of analyses were performed: cell and pixel based. For the cell-based analysis, asbestos cement (AC) pipes exhibited the highest failure rates. Older AC pipes were also shown to fail more often, whereas failure rates for PVC were the lowest. For the pixel-based analysis, ground movement was demonstrated to play a role in the failure of all materials combined. Therefore, a replacement-prioritisation map for AC was generated which combined ground movement data and pipe-age data. This method can be a beneficial resource for network managers for maintenance and continuous monitoring.     

Pipe failure rate prediction in water distribution networks using multivariate adaptive regression splines and random forest techniques

ABSTRACT

This paper presents the results of a comparison between multivariate adaptive regression splines (MARS) and random forest (RF) techniques in pipe failure prediction in two water distribution networks. In this regard, pipe diameter, pipe length, pipe installation depth, pipe age and average hydraulic pressure are considered as input variables. Results show that the RF outperforms the MARS which is found as an accurate pipe failure rate predictor. The proposed models are further evaluated through dividing the data into three parts of lower, medium and higher pipe failure rate values. According to the equations produced by MARS technique, three variables of pipe diameter, pipe age and average hydraulic pressure are distinguished as the most effective variables in predicting pipe failure rate in the first case study. Four variables of pipe diameter, pipe length, pipe age and average hydraulic pressure are determined as the most effective variables in the second case study.     

Equity in water supply in intermittent water distribution networks

Equity in water supply is one of the major problems faced in intermittent water distribution systems. A new index ‘uniformity coefficient’ is introduced to measure the equity in distribution of water within the network, which may be useful for performance evaluation of water distribution networks (WDNs). An iterative head‐driven analysis technique is developed to compute the uniformity coefficient of a network. The effect of various design parameters of WDN on the uniform coefficient is studied. The results indicate that equity in water supply is significantly affected by the location of the tank and layout of the network. The equity in water supply can be improved in an existing network by staggered supply.     

Multi-objective optimization of water distribution networks

Two multi-objective approaches to the consideration of pipe breakage data in water distribution network designs are formulated. Both models are based on the constraint method for multi-objective analysis. One model analyses the relationship between initial capital cost and subsequent repair and maintenance costs. Pipe breakage data is used to restrict the repair costs permitted in the system. The other model examines the relationships between initial pipe costs and the reliability of the pipes within the distribution network. In this second model, both the worst case and average system performance are examined in relation to the cost making model a three-objective approach. The pipe breakage data is used to restrict the expected number of failures allowed in any link. The actual number of expected breaks occurring in each link is then used to develop Poisson-based probabilities of node isolation. Application of the two approaches shows that the information obtained from such multi-objective approaches gives improved understanding into the nature of the issues behind initial cost and repair cost and initial cost and system reliability.     

Enhancement of limited water supply network data for deterioration modelling and determination of rehabilitation rate

In the past decades, the main focus of water supply management has moved from construction of new water supply networks to rehabilitation and adaptation of the existing infrastructure. The decision-making process for the rehabilitation management relies heavily on the quality of the applied deterioration model. A recurring problem in the application of such models relates to the quality and availability of network data. These data are often incomplete or unreliable because building measures and damages are only documented properly recently and the recovery of older data is difficult and expensive. A key point in rehabilitation planning is therefore data collection and data reconstruction. Consequently, the aim of this paper is to present a methodology for the enhancement of the available data of water supply networks and the prognosis of the necessary rehabilitation rates under limited data availability. Results indicate that the presented data reconstruction technique has advantages as compared to traditional data extrapolation. It also allows the reconstruction of fragmentary data about existing water supply and wastewater collection systems for the operating utilities. However, it cannot be used for reconstructing failure types as well as the whole information on pipes (e.g. more than two missing information).     

Chlorine demand-based predictive modeling of THM formation in water distribution networks

The potential carcinogenicity of trihalomethanes (THMs) has led to increasingly stricter regulation of drinking water supplies. This has led to the need to manage better the chemical and microbiological risk balance in chlorinated supplies. The use of empirical equations to predict THM concentrations in water quality models is challenging and expensive due to the numerous temporally and spatially dependent uncertainties involved. In this paper, the benefits of a simple predictive method using a THM productivity parameter based on chlorine consumed by bulk free chlorine reactions are explored using extensive field data from a water distribution system in the Midlands region of the UK. It is concluded that the productivity parameter provides an appropriate, relatively robust, yet straightforward alternative to the use of an empirical equation based on regression analyses to predict THM concentrations in distribution, and that the method has the potential to help distribution system water quality model calibration.     

Teaching operations research and decision analysis to graduate students in water resources

The department of civil engineering at the University of British Columbia has. over the past 15years, developed a number of courses in optimization and decision analysis. These courses originally emerged from research interests in water resources and the needs of the water resources program but have since become entrenched in the undergraduate core and are now expanding into a department-wide program at the graduate level. Experiences during the evolution of the programme are described. An outline of the author's views of a comprehensive teaching programme, which is now largely in place, is presented together with some of the difficulties the programme hopes to resolve.     

内穿插HDPE管修复大口径给水管实例

结合福州市北区水厂原水管修复实例,介绍了内穿插HDPE管修复技术的原理、施工工艺、主要工序及其技术指标、优缺点、衬管壁厚的选择。结果证明,利用该技术修复大口径给水管可减少投资、节省工时、对环境破坏少,宜于推广应用。     

Multi-criteria decision analysis for infrastructure privatisation using conflict resolution

A decision support system (DSS) is introduced for evaluating and comparing a wide range of privatisation schemes for infrastructure facilities. The methodology identifies the preferences of the main stakeholders involved, along with all the environmental, political, technical and economic criteria that need to be considered in privatisation decisions. A DSS is then developed and tested on a case study involving the privatisation of a wastewater project. The system provides decision support through three steps: (1) screening of infeasible decisions using the elimination method of multiple criteria decision analysis; (2) determining the most stable decision by analysing the actions and counteractions of the stakeholders using conflict resolution and stability analysis; and (3) evaluating the robustness of decisions under varying levels of uncertainty using information gap theory. The DSS is useful for practitioners involved in infrastructure privatisation decisions for a variety of infrastructure systems such as transportation, water and energy.     

Simulation-based life cycle cost modeling and maintenance plan for water mains

Life cycle cost (LCC) is an essential approach to decide on alternative rehabilitation strategies for infrastructure systems, such as water mains. The research presented in this article identifies several rehabilitation methods for water mains, which are classified into three main categories: repair, renovation and replacement. A simulation-based LCC (SLCC) model is developed to compare different rehabilitation scenarios/alternatives for various types of water mains (i.e. cast iron, ductile iron, concrete, polyvinyl chloride and asbestos cement). Results show that ‘open trench’ and ‘slip lining’ are the most appropriate methods for the ‘repair’ and ‘renovation’ categories, respectively. However, the most suitable method for the ‘replacement’ category is ‘pipe bursting’ for pipe diameters less than 750 mm (<30″) and ‘open cut’ for pipe diameters greater than 750 mm (>30″). A rehabilitation plan is developed based on the SLCC results. This plan recommends repairing pipes using ‘open trench’ until the breakage rate reaches 0.5 breaks/km/year, then, replace the pipe beyond this threshold. Based on the designed SLCC model, web-based software is developed to determine the optimal rehabilitation scenarios. The developed model and software help academics and practitioners (e.g. municipal engineers) to predict the suitable new installation and/or rehabilitation programs as well as their corresponding costs.     

Concept and prototype of a spatial decision support system for integrated water management applied to Ichkeul Basin,Tunisia

In this study, we develop a spatial decision support system (SDSS) for water management in a basin characterised by existing and projected dams to satisfy freshwater demand while preserving a particular ecosystem. The territorial and functional interests along with management scenarios were integrated into consistent stages of the SDSS. The developed prototype allowed comparisons of multiple water allocation options to competing users in the catchment by two aggregation methods. Through a simulation modelling exercise and stakeholder's involvement, the main outputs are the development of water management options and a set of criteria/subcriteria to evaluate these options related to socio‐economic, water availability and ecological factors. Both aggregation methods reveal the positive effect of water transfer on overall evaluations. New dam construction would cause an increase in the overall evaluation from the SDSS by at best 34% when water availability criteria are favoured, while a decrease in overall evaluation by at worst 75% is indicated when ecological criteria are favoured.     

Experiences of stakeholder participation in multi-criteria decision analysis (MCDA) processes for water infrastructure

Abstract

The process of multi-criteria decision analysis is commonly utilized in planning processes for technical infrastructure. This includes water infrastructure, which is currently impacted by global changes in environmental conditions. Consequentially, technical and conceptual options have been developed with the focus on sustainability by closing water and material cycles. The inclusion of stakeholder perspectives in the planning process would be supported by purposeful MCDA implementation. This paper examines initial stages of the MCDA with a focus on the multi-stakeholder-group-driven collaborative development of a set of objectives (SOO). Additional emphasis is given to participatory methods for each stage of the two, presented case studies examined in this paper. An attempt has been made to describe perceptions and outcomes of the case studies. The developed SOOs are presented and discussed with special regard to the development process and the evaluation outcomes.     

水资源规划及其应用

通过对水资源规划的内容及其基本方法的分析,介绍了目前GIS、决策支持系统、水资源-宏观经济-生态环境系统耦合在水资源规划和管理中的应用,指出了水资源规划的总目标,以满足社会对水的需求.     

Developing efficient management strategies for a water supply system using system dynamics modelling

In this paper, the causal feedback relationships among the components that make up the working mechanism of water supply systems management, including key factors and their relationship to the management of water pipes, were identified based on the conceptual framework established for water supply systems management. Subsequently, a system dynamics computer simulation model, which can be used to aid efficient management of water supply systems, was developed. The computer model consisted of water supply, pipe maintenance, and water supply business finance sub-models. The model was verified using historical data from a water supply service case study. Using the verified model, long-term managerial and operating conditions of the case study system were predicted under optimistic, basic, and pessimistic management condition scenarios. In addition, sensitivity analyses on major indicators of the case study system have been presented to show that the developed model can facilitate identification of the best policy for achieving a specific management objective of a water supply system.     

Evaluation of data driven models for pipe burst prediction in urban water distribution systems

ABSTRACT

The water distribution network is one of the most expensive parts of a water supply system. The fundamental variables of a network, material, diameter, length, age, and the hydraulic pressure of pipes are the factors that affect the pipe burst rate (PBR). Establishing a relationship among the burst rate and these factors is an important step to assess the conditions governing the network and preventing significant water leakage. Implementing the data-driven approach in PBR prediction is an effective method to find the relationship. In the present study, Grasshopper Optimization Algorithm-based Support Vector Regression (GOA-SVR), Gaussian Process Regression (GPR), and Artificial Neural Network (ANN) have been developed to predict PBR in an urban area. The results show that the GPR model outperforms other methods. Furthermore, the sensitivity analysis indicates that the pipe age has a negative effect on PBR modeling while the pipe length is the most relevant variable.     

太原市城市给水工程输水钢管阴极保护技术

针对太原市城市给水工程DN2200输水钢管采用阴极保护的工程实例,介绍了牺牲阳极法,对工程方案的选择、参数的选择与确定进行了详细阐述,提出了工程安装措施及其验收装置。