District Metered Areas Design Under Different Decision Makers’ Options: Cost Analysis

Water loss is a big challenge for water supply companies worldwide, and the Water Network Partitioning (WNP) is an excellent tool for water loss management–particularly in the current difficult economic and financial conditions. WNP is a recent research line and consists in dividing the water distribution network into smaller zones called District Metered Areas (DMAs) with one (or more, in exceptional cases) supply point, to reduce the network complexity and/or allow pressure management. Since there are several possible future scenarios, such as the water demand and/or the infrastructure degradation forecasts, which may have different impacts on the hydraulic behaviour, in this paper a computational application, based on an optimization model, is proposed to achieve a compromise between robustness required for the DMAs design (using a baseline scenario) and different decision makers’ options (using other scenarios with a lower “probability” of occurrence), to reduce the total cost. The objective function reflects the minimization of the squared deviations between the total cost of the DMAs design and the minimum cost for each scenario forecasted for the project plan, multiplied by the weight or “probability” of occurrence for each of the scenarios. The performance of the computational application is illustrated with a case study, and the results are encouraging.     

Decision support system to divide a large network into suitable District Metered Areas

This paper presents a new approach to divide large Water Distribution Networks (WDN) into suitable District Metered Areas (DMAs). It uses a hydraulic simulator and two operational models to identify the optimal number of DMAs, their entry points and boundary valves, and the network reinforcement/replacement needs throughout the project plan. The first model divides the WDN into suitable DMAs based on graph theory concepts and some user-defined criteria. The second model uses a simulated annealing algorithm to identify the optimal number and location of entry points and boundary valves, and the pipes reinforcement/replacement, necessary to meet the velocity and pressure requirements. The objective function is the difference between the economic benefits in terms of water loss reduction (arising from the average pressure reduction) and the cost of implementing the DMAs. To illustrate the proposed methodology, the results from a hypothetical case study are presented and discussed.     

Location and Calibration of Valves in Water Distribution Networks Using a Scatter-Search Meta-heuristic Approach

Recently, there has been an increase in the use of meta-heuristic techniques addressing water distribution network design and management optimization problems. The meta-heuristic approach applied to water distribution systems has provided interesting results both for optimum pipe diameter sizing and for the location and management of network pressure control devices (i.e., pumps and valves). Regarding the insertion and calibration of pressure regulation valves, the use of meta-heuristic techniques is relatively recent. We search to strategically placing the valves in order to achieve pressure control in the network and, therefore, the valves must be calibrated in relation to water demand trends over time. In the Pressure Reference Method (PRM) described in this paper, the search for valve location is restricted to pipe-branch sets defined on the basis of hydraulic analysis and considering the range between minimum and maximum acceptable pressures in the network. In the PRM approach, the Scatter-Search (Glover and Laguna, 1997) meta-heuristic procedures are applied to obtain the optimal location and calibration of valves in the water distribution network.     

Pressure Control for Leakage Minimisation in Water Distribution Systems Management

A model to support decision systems regarding the quantification, location and opening adjustment of control valves in a network system, with the main objective to minimise pressures and consequently leakage levels is developed. This research work aims at a solution that allows simultaneously optimising the number of valves and its location, as well as valves opening adjustments for simulation in an extended period, dependently of the system characteristics. EPANET model is used for hydraulic network analysis and two operational models are developed based on the Genetic Algorithm optimisation method for pressure control, and consequently leakage reduction, since a leak is a pressure dependent function. In these two modules, this method has guaranteed an adequate technique performance, which demands a global evaluation of the system for different scenarios. A case study is presented to show the efficiency of the system by pressure control through valves management.     

Automatic Multiscale Approach for Water Networks Partitioning into Dynamic District Metered Areas

Water distribution systems (WDSs) today are expected to continuously provide clean water while meeting users demand, and pressure requirements. To accomplish these targets is not an easy task due to extreme weather events, operative accidents and intentional attacks; as well as the progressive deterioration of the WDS assets. Therefore, water utilities should be ready to deal with a range of disruption scenarios such as abrupt variations on the water demand e.g. caused by pipe bursts or topological changes in the water network. This paper presents a novel methodology to automatically split a WDS into self-adapting district metered areas (DMAs) of different size in response to such scenarios. Complex Networks Theory is proposed for creating novel multiscale network layouts for a WDS. This makes it possible to automatically define the dynamic partitioning of WDSs to support further DMA aggregation / disaggregation operations. A real, already partitioned, water utility network shows the usefulness of an adaptive partitioning when the network is affected by an abnormal increase of the peak demand of up to 15%. The dynamic DMA reuses the assets of the static partitioning and, in this case, up to the 82% of resilience is restored using 94% of the assets already installed. The results also show that the overall computational and economic management costs are reduced compared to the static DMA partition while the hydraulic performance of the WDS is simultaneously preserved.

     

石虎塘航电枢纽工程电站取水口水流条件试验研究

通过水工模型试验,对赣江石虎塘航电枢纽[1]的电站取水口局部区域的水力、泥沙运动规律进行了研究,在确保电站无论在正常蓄水位情况还是在全闸敞泄情况下,电站均能够引用到足够的水量用以发电,在研究电站取水口原布置方案的基础上,对其布置形式进行了优化。试验表明,模型所提出的优化布置形式能够最大限度地满足电站取水发电要求,水流条件也平稳顺畅,避免了取水口处泥沙淤积而导致引水不畅问题,有利于电站取水口的安全、可靠运行,符合实际要求。     

Pressure Management Model for Urban Water Distribution Networks

A technique for leakage reduction is pressure management, which considers the direct relationship between leakage and pressure. To control the hydraulic pressure in a water distribution system, water levels in the storage tanks should be maintained as much as the variations in the water demand allows. The problem is bounded by minimum and maximum allowable pressure at the demand nodes. In this study, a Genetic Algorithm (GA) based optimization model is used to develop the optimal hourly water level variations in a storage tank in different seasons in order to minimize the leakage level. Resiliency and failure indices of the system have been considered as constraints in the optimization model to achieve the minimum required performance. In the proposed model, the results of a water distribution simulation model are used to train an Artificial Neural Network (ANN) model. Outputs of the ANN model as a hydraulic pressure function is then linked to a GA based optimization model to simulate hydraulic pressure and leakage at each node of the water distribution network based on the water level in the storage tank, water consumption and elevation of each node. The proposed model is applied for pressure management of a major pressure zone with an integrated storage facility in the northwest part of Tehran Metropolitan area. The results show that network leakage can be reduced more than 30% during a year when tank water level is optimized by the proposed model.     

HydroGen: an Artificial Water Distribution Network Generator

Many (metaheuristic) techniques for water distribution network (WDN) design optimisation already have been developed. Despite of the aforementioned scientific attention, only few, high-quality benchmark networks are available for algorithm testing, which, in turn, hinders profound algorithm testing, sensitivity analysis and comparison of the developed techniques. This absence of high-quality benchmark networks motivated us to develop a tool to algorithmically generate close-to-reality virtual WDNs. The tool, called HydroGen, can generate WDNs of arbitrary size and varying characteristics in EPANET or GraphML format. The generated WDNs are compared to (and shown to closely resemble) real WDNs in an analysis based on graph-theoretical indices. HydroGen is used to generate an extensive library of realistic test networks on which (metaheuristic) methods for the optimisation of WDN design can be tested, allowing researchers in this area to run sensitivity analyses and to draw conclusions on the robustness and performance of their methods.     

严寒地区大型倒虹吸工程管道应力及水力安全控制

新疆北疆供水工程跨越吉拉沟大洼槽的三个泉倒虹吸,跨度11 km,内径2.8 m,工作水头160m,是国内外同类工程中综合难度较高的大型倒虹吸工程,在结构强度、材料工艺、安装敷设、工程质量方面都有极高的要求,特别是高水头管道运行、充水、放空、水锤防护等各种工况下的水力安全控制问题,高温差与严寒条件下管道的应力应变问题尤为突出。对该工程设计、科研、施工及运行管理方面的经验进行介绍,对其在新技术、新材料、新工艺等方面取得的理论研究和技术创新成果进行总结,研究认为:工程总体布置合理,工程运行后监测资料及工程安全评价表明各项性状指标良好,通过模型试验研究确定的闸门开度、关闭速率、充水排气、放空排水等水力安全控制关键技术科学合理,为严寒地区大型倒虹吸工程的技术发展提供借鉴。     

三峡水利枢纽技术设计中一些重大技术问题的论述

三峡水利枢纽在技术设计中，研究解决、决策了大坝泄洪消能，岸坡厂房坝段基础深层稳定，电站引水管道结构型式，电站排沙排漂，永久船闸输水系统及水力学，引航道布置及通航水流条件、高边坡稳定，升船机承重结构稳定，水轮发电机组及金属结构中的永久船闸人字门、启闭机、充水泄水阀门，升船机承船厢提升及平衡系统等一些重大技术问题。     

Implementation of Hydraulic Modelling for Water-Loss Reduction Through Pressure Management

This study was conducted in the Konyaalti Water Distribution Network in Antalya, Turkey. The study area was divided into 18 district metered areas (DMAs) for better management of water losses. Water levels in reservoirs, flow rates, and water pressures were monitored on-line by the SCADA data system. A hydraulic model was calibrated and verified for each DMA using data provided by SCADA. The model results revealed that a number of DMAs exhibited high pressures, greater than 3.5 bars, and high minimum night flow (MNF) throughout the year. Also, the Infrastructure Leakage Index (ILI) for the study area was greater than 20, indicating high water losses. As a result of these findings, a pressure reducing valve (PRV) was installed at DMA No. 2 as an example and set at 3.0 bars resulting in considerable reduction in water losses. The optimum pressure level for setting the PRV was chosen using the hydraulic model. The same model was used to predict water savings due to pressure reduction. The predicted water savings were verified using long periods of flow rates and water pressure profiles. The predicted and measured water savings showed good agreement. The study concluded that hydraulic modelling is essential for applying appropriate pressure management strategies.     

A Simplified Methodology for Optimal Location and Setting of Valves to Improve Equity in Intermittent Water Distribution Systems

In this paper, a simplified methodology to increase the water distribution equity in existing intermittent water distribution systems (WDSs) is presented. The methodology assumes to install valves in the water distribution network with the objective to re-arrange the flow circulation, thus allowing an improved water distribution among the network users. Valve installation in the WDS is based on the use of algorithms of sequential addition (SA). Two optimization schemes based on SA were developed and tested. The first one allows identifying locations of gate valves in order to maximize the global distribution equity of the network, irrespectively of the local impact of the valves on the supply level of the single nodes. Conversely, the second scheme aims to maximize the global equity of the network by optimizing both location and setting (opening degree) of control valves, to include the impact of the new flow circulation on the supply level of each node. The two optimization schemes were applied to a case study network subject to water shortage conditions. The software EPA Storm Water Management Model (SWMM) was used for the simulations in the wake of previous successful applications for the analysis of intermittent water distribution systems. Results of the application of the SA algorithms were also compared with those from the literature and obtained by the use of the multi-objective Non-Dominated Sorted Genetic Algorithm II (NSGA II). The results show the high performance of SA algorithms in identifying optimal position and settings of the valves in the WDS. The comparison pointed out that SA algorithms are able to perform similarly to NSGA II and, at the same time, to reduce significantly the computational effort associated to the optimization process.

     

泰州引江河高港二线船闸输水系统布置及水力计算分析

结合高港二线船闸工程具体条件,按照《船闸输水系统设计规范》的要求,研究确定了船闸短廊道和三角门门缝联合输水的输水系统型式及具体布置方案,计算分析了充泄水阀门开启方式,通过建立船闸联合输水数学模型计算了闸室输水水力特性.结果表明,确定的船闸输水系统布置及阀门开启方式是合适的,相关水力指标满足规范及设计要求;设计的消能工布置适合高港二线船闸工程特点,可获得较好的闸室水流条件;同时根据水力特性计算结果提出了阀门启闭系统设计建议.     

浅谈城市景观水闸的几种设计布置形式

针对日益提高的城市水闸的景观要求，该文简要介绍几种常见的城市景观水闸的布置形式，主要集中为采用液压启闭机的布置形式，并重点阐述各自的布置特点，包括水闸适用工况、布置形式的优劣势等。供同行设计借鉴。     

Optimal Placement of Isolation Valves in Water Distribution Systems Based on Valve Cost and Weighted Average Demand Shortfall

In this paper a method for optimal placement of isolation valves in water distribution systems is presented. These valves serve to isolate parts of the network (segments) containing one or more pipes on which maintenance work can be performed without disrupting service in the entire network or in large portions of it. The segments formed after the installation and closure of isolation valves are identified and characterised using an algorithm which is based on the use of topological matrixes associated with the structure of the original network and the one modified to take account of the presence of (closed) valves. A multi-objective genetic algorithm is used instead to search for the optimal position of the valves. In the application of the method different objective functions were used and compared to solve the problem as to the optimal placement of the valves. The results showed that the most appropriate ones are the total cost of the valves (to be minimised) and the weighted average “water demand shortfall” (likewise to be minimised); in particular, the weighted average shortfall is calculated considering the shortfalls associated with the various segments of the network (shortfall is the unsupplied demand after isolating a segment) and the likelihood of failures tied to mechanical factors occurring in the segments. The methodology was applied to a case study focusing on a simplified layout of the water distribution system of the city of Ferrara (Italy).     

引江补汉工程段中分层减压控制闸布置与体型研究

引江补汉工程段中控制方案将控制闸设置在 164?km 处，以避免局部段内压过高的问题，主要从水动力特性 的角度论证洞线总体布置及控制闸布置与体型的合理性。采用一、三维数学模型与物理模型相结合的复合模型 开展相关研究：一维水锤数学模型用于闸门启闭过程的全线水力过渡过程分析，通过优化计算，得到相对较优的 闸门启闭过程，同时为控制闸段的三维数模与物理模型提供边界条件；三维水气两相流数学模型与物理模型模拟 分析闸室与调流池流态与水面波动、中孔溢流面压力分布等水力指标，同时为一维数学模型提供控制闸泄流能力 曲线。结果表明：当控制中孔弧形门以先慢后快的三阶段变速率过程开启时，可将全线的最大水锤压力压值在规 程允许范围内；中孔溢流面压力分布正常，调流池内水体消能充分，下有压洞进口前沿水面波动较小，未见吸气旋 涡等不利流态。引江补汉工程工程采用段中分层减压控制的总体方案是可行的，控制闸布置与体型合理，研究方 法可供类似工程参考。     

小浪底水利枢纽偏心铰弧形闸门液压启闭机设计

小浪底水利枢纽偏心铰弧门每台液压启闭机由两套油缸和一套液压泵站组成。系统设计中，首次采用蓄能器作为防止闸门下沉的措施；采用插装阀替代传统的普通滑阀，有效地解决了阀件的泄漏问题；油缸密封圈采用进口优质产品，油箱、管道采用不锈钢材料，从而增强了液压启闭机的运行可靠性。     

疏勒河青羊沟水电站枢纽挑流消能鼻坎设计与优化

青羊沟水电站枢纽采用挑流消能设计,枢纽布置为3孔泄洪表孔和1孔泄洪冲沙表孔。枢纽下游河床非常狭窄,宽度仅为20余m,消能防冲设计难度大,对挑流鼻坎在不同流量下的水力性能要求很高。原设计采用宽尾墩结合扭曲式鼻坎消能,左右表孔出口水流对两岸坡脚有直接冲刷,且对下游河道的冲刷深度较大。针对原设计水流冲刷两岸及冲深较大的问题,结合枢纽水工模型试验,优化了鼻坎体型,使挑坎结构布置安全、合理,并满足运行要求。     

基于GIS的供水管网爆管分析的算法

根据系统和爆管分析的需求以及供水数据的特点建立逻辑网络模型,基于逻辑网络模型与图论的方法进行爆管分析的算法设计,通过对拓扑邻接表进行广度优先搜索,初步寻找需要关闭的阀门,然后通过分析这些阀门间的控制关系和与水源的连通性,剔除了可关可不关的阀门,得到正确、经济的关阀门方案,并列出了受影响的用户.并将上述思想与设计方案应用于"新疆克拉玛依供水地理信息系统"中,成功地实现了爆管分析,验证了上述方法的正确性与可行性.     

Nodal Analysis of Urban Water Distribution Networks

There are three methods for analysing the flow and pressure distribution in looped water supply networks (the loop method, the node method, the pipe method), accounting for the chosen unknown hydraulic parameters. For all of these methods, the nonlinear system of equations can be solved using iterative procedures (Hardy–Cross, Newton–Raphson, linear theory). In the cases of the extension or the rehabilitation of distribution networks, the unknown parameters are the hydraulic heads at nodes, and the nodal method for network analysis is preferred. In this paper, a generalised classic model is developed for the nodal analysis of complex looped systems with non-standard network components and the solvability of new problems, along with the determination of the pressure state in the system. In addition, this paper exhibits a different approach to this problem by using the variational formulation method for the development of a new analysis model based on unconditioned optimisation techniques. This model has the advantage of using a specialised optimisation algorithm, which directly minimises an objective multivariable function without constraints, implemented in a computer program. The two proposed models are compared with the classic Hardy–Cross method, and the results indicated a good performance of these models. Finally, a study is performed regarding the implications of the long-term operation of the pipe network on energy consumption using these models. The new models can serve as guidelines to supplement existing procedures of network analysis.