Optimal Pressure Regulation in Water Distribution Systems Based on an Extended Model for Pressure Reducing Valves

Optimal pressure regulation to reduce water losses in water distribution systems (WDSs) becomes an important concern due to the increasing water demand and the threat of drought in many areas of the world. The leakage amount in a WDS depends heavily on its operating pressure and thus can be minimized by implementing optimal pressure strategies through pressure reducing valves (PRVs). To achieve this, a model-based optimization is necessary, where an accurate model of the PRVs is required. The PRV models having been used until now for pressure regulations are two-mode models which cannot circumstantiate many situations occurring in WDSs. In this paper, we extend the existing model by a three-mode one for PRVs which is able to describe the required circumstances of pressure regulations in WDSs. The non-smoothness of this model is smoothed by an approximation approach, thus allowing the formulation and solution of a continuous nonlinear optimization problem for optimal pressure regulation. Two benchmark WDSs are used to verify our approach and it can be shown from the results that our PRV model outperforms the existing models in terms of the quality and accuracy of the optimal solutions.

     

Random Walks Partitioning and Network Reliability Assessing in Water Distribution System

A novel network partition model is presented within the water distribution system (WDS). Firstly, random walk community detection (RWCD) is employed to divide WDS into different partitions concerning the average pressure of nodes. Then, network reliability is assessed based on hydraulic reliability estimation (HRE), mechanical reliability estimation (MRE), flow entropy function (FEF), and network resilience (NR), via optimizing boundary pipes by the non-dominated sorting genetic algorithm-II (NSGA-II). Finally, pressure-reducing valves (PRVs) are set to pipes for acquiring optimized partitions. The Open Water Analytics (OWA) toolbox and Matlab-2018b is adopted as a hydraulic calculation tool for these extended period simulations (EPS). Seven cases of WDSs were used to verify the practicability of this model. The results demonstrate that network reliability is improved effectively after partitioning and optimizing.

Graphical Abstract

     

Optimal Location and Setting of PRVs in WDS for Leakage Minimization

Water loss is an issue that affect Water Distribution Systems (WDSs) very often, especially when aged and high pressure occurs. Pressure reduction valves (PRVs) can be used as devices to reduce as much as possible the water losses within the network. Indeed, for a given number of PRVs, the daily volume of water lost from the network can be reduced minimizing the pressure through a proper choice of valve positions as well as their settings. In this paper, a methodology for the optimal number, positioning and setting of PRVs is presented. In the proposed methodology, a genetic algorithm is coupled with a physical modelling of leakage from joints and a simplified and yet realistic hydraulic simulation of the WDS. The proposed methodology is demonstrated using two WDSs examples. Comparisons with a more extreme and complicated hydraulic modelling, already proposed by authors in previous work, are also performed in the first case study in order to validate the proposed methodology. These comparisons demonstrate that the methodology proposed in this work performs fairly well when compared to similar approach that uses a more sophisticated hydraulic model. As a consequence, it revealed to be a good tool for the optimal positioning and sizing of PRVs within WDS aimed at reducing the background leakages even when the WDS is characterized by complex geometry and topology.     

Design of a Control System Using an Artificial Neural Network to Optimize the Energy Efficiency of Water Distribution Systems

Sustainable management of water supply systems is a major challenge within the framework of the water-energy nexus. The main strategies to improve the operation of these systems are related to increasing the hydraulic and energy efficiency of pumping systems. In this context, this work presents a new artificial neural network (ANN) controller to improve the operation of water distribution systems (WDSs) that includes in its algorithm the specific energy consumption (SEC) as a decision parameter. Therefore, pressure control at the measuring points is also based on the energy efficiency of the pumps. The technique was applied to control the pressures in an experimental setup that emulates a WDS with two consumption zones with different topographies. For this purpose, the controller acted on a conventional pump, a booster pump and a control valve. To analyze the performance under the controller action, tests were performed emulating water-demand scenarios, introducing perturbations and changing the pressure setpoints. The real-time control performance was proven based on the dynamic performance, steady-state performance and SEC. The experimental results showed that the proposed controller kept the pressures close to the setpoints and provided a reduction in the SEC between 15.1% and 17.8%, compared with the uncontrolled system, and an economy that varied from 2.5% to 8.1% compared with the performance of the ANN based only on pressure control.

     

Sustainability Assessment of Urban Water Distribution Systems

A methodology is presented for determining sustainability indices for pressure and water age in water distribution systems (WDSs). These sustainability indices are based upon performance criteria including reliability, resiliency, and vulnerability. Pressure and water age are determined for a WDS as a function of operation time using the U.S. Environmental Protection Agency EPANET model. The values of pressure and water age are used to determine reliability, resiliency, and vulnerability performance criteria, which are then combined into the nodal sustainability indices for water age and pressure. In addition, the sustainability index (SI) computations are performed for zones to define the SI for water age and SI for pressure. A combined SI calculation is performed to produce an overall sustainability score for the entire zone in the water distribution network. The proposed methodology can be used to monitor the sustainability of existing WDSs and to help define alternative solutions including changes in pump operation and modifications to WDS to increase the sustainability.     

Technical and Environmental Sustainability Assessment of Water Distribution Systems

An environmental and technical sustainability assessment methodology is developed for both centralized and dual water distribution systems (WDSs) with and without fire flow scenarios. Technical sustainability of potable and reclaimed water networks is measured by a sustainability index (SI) assessment using reliability, resiliency, and vulnerability performance criteria. The U.S. Environmental Protection Agency EPANET software is used to simulate hydraulic (i.e. nodal pressure) and water quality (i.e. water age) analysis in a WDS. Total fresh water use and total energy intensity are considered as environmental sustainability criteria. The procedure considers two separate alternatives for meeting fire flows: (1) adding pumping to a system or (2) adding a non-potable WDS. The reclaimed system is designed using linear programming (LP) optimization. For each alternative, multi-criteria decision analysis (MCDA) is used to combine technical and environmental sustainability criteria for an urban WDS.     

Ensemble CNN Model for Effective Pipe Burst Detection in Water Distribution Systems

Various data-driven anomaly detection methods have been developed for identifying pipe burst events in water distribution systems (WDSs); however, their detection effectiveness varies based on network characteristics (e.g., size and topology) and the magnitude or location of bursts. This study proposes an ensemble convolutional neural network (CNN) model that employs several burst detection tools with different detection mechanisms. The model converts the detection results produced by six different statistical process control (SPC) methods into a single compromise indicator and derives reliable final detection decisions using a CNN. A total of thirty-six binary detection results (i.e., detected or not) for a single event were transformed into a six-by-six grayscale heatmap by considering multiple parameter combinations for each SPC method. Three different heatmap configuration layouts were considered for identifying the best layout that provides higher CNN classification accuracy. The proposed ensemble CNN pipe burst detection approach was applied to a network in Austin, TX and improved the detection probability approximately 2% higher than that of the best SPC method. Results presented in this paper indicate that the proposed ensemble model is more effective than traditional detection tools for WDS burst detection. These results suggest that the ensemble model can be effectively applied to many detection problems with primary binary results in WDSs and pipe burst events.

     

Pressure-Dependent EPANET Extension

In water distribution systems (WDSs), the available flow at a demand node is dependent on the pressure at that node. When a network is lacking in pressure, not all consumer demands will be met in full. In this context, the assumption that all demands are fully satisfied regardless of the pressure in the system becomes unreasonable and represents the main limitation of the conventional demand driven analysis (DDA) approach to WDS modelling. A realistic depiction of the network performance can only be attained by considering demands to be pressure dependent. This paper presents an extension of the renowned DDA based hydraulic simulator EPANET 2 to incorporate pressure-dependent demands. This extension is termed “EPANET-PDX” (pressure-dependent extension) herein. The utilization of a continuous nodal pressure-flow function coupled with a line search and backtracking procedure greatly enhance the algorithm’s convergence rate and robustness. Simulations of real life networks consisting of multiple sources, pipes, valves and pumps were successfully executed and results are presented herein. Excellent modelling performance was achieved for analysing both normal and pressure deficient conditions of the WDSs. Detailed computational efficiency results of EPANET-PDX with reference to EPANET 2 are included as well.     

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.

     

Investigating Energy Flow in Water-Energy Storage for Hydropower Generation in Water Distribution Systems

Quantifying excess energy using an energy balance model is the key to designing and operating an energy-efficient water distribution system (WDS). Excess energy, which can be recovered instantly or stored in a water-energy storage is the basis to estimate hydropower potential in the system. For a given WDS with its demand, how the excess energy can be managed efficiently to design a water-energy storage to maximize hydropower generation is the focus of this paper. A single-objective optimization model has been developed to optimize the dimensions for up to six water-energy storages for maximizing hydropower generation while minimizing the pumping energy. While the ratio of total energy recovered to total pumping energy is found to be about 40% for all water-energy configurations, the recovered specific energy ranges from 0.116 kWh/m³ to 0.121 kWh/m³ showing the potential use of WDS as an energy storage. Results show that hydropower generation increases with the increase of number of storages up to a certain number representing the constraints of constant drinking water demand and storage dimensions. In-pipe turbines with pump operation for minimizing pumping energy can offer the optimal solution for WDS energy management. A higher number of storages with in-pipe turbines offers uniformity in pressure distribution resulting increase in system robustness.

     

Multiobjective Memetic Algorithm Applied to the Optimisation of Water Distribution Systems

Finding low-cost designs of water distribution systems (WDSs) which satisfy appropriate levels of network performance within a manageable time is a complex problem of increasing importance. A novel multi-objective memetic algorithm (MA) is introduced as a solution method to this type of problem. The MA hybridises a robust genetic algorithm (GA) with a local improvement operator consisting of the classic Hooke and Jeeves direct search method and a cultural learning component. The performance of the MA and the GA on which it is based are compared in the solution of two benchmark WDS problems of increasing size and difficulty. Solutions that are superior to those reported previously in the literature were achieved. The MA is shown to outperform the GA in each case, indicating that this may be a useful tool in the solution of real-world WDS problems. The potential benefits from search space reduction are also demonstrated.     

Sensor Partitioning Placements via Random Walk and Water Quality and Leakage Detection Models within Water Distribution Systems

A novel sensor partitioning placement model is presented to evenly distribute sensors to water distribution systems (WDS) for monitoring leakages and contamination. First, random walk community detection (RWCD) is used to divide WDS into different partitions. Then, an extended period leakage detection (EPLD) model is presented. The total leakage detection and the average time of leakage detection are used as objective functions for pressure sensor placement. Next, the extended period water quality detection (EPWQD) model is presented. The total intrusion detection, the average percentage of clean water, and the average time of water quality detection are used as objective functions for water quality sensor placement. Evolutionary algorithm (EA) modules are applied to optimize the locations of pressure and water quality sensors. Seven networks are employed to verify the practicability of the model. The results show that leakage and intrusion detection rate is up to 85% during 24 h, and the average percentage of clean water is up to 0.9 in these cases. Finally, the model compares the leakage zone identification (LZI) and the water quality sensor placement strategy (WQSPS) models. The total detection number, the total average time of detection, and the total average percentage of clean water have been improved. Therefore, this model is a high-potential way of sensor placement.

Graphical Abstract

     

Modularity-Based Procedure for Partitioning Water Distribution Systems into Independent Districts

A proper division of a Water Distribution System (WDS) into District Metered Areas (DMAs) provides important management benefits particularly with regard to leakage detection through water balances, control and optimization of pressure so as to reduce leakage, implementation of monitoring, warning and emergency acting systems against accidental or intentional water contamination. This paper presents a new methodology that combines a suitable modularity-based algorithm for the automated creation of DMA boundaries and convincing practical criteria for the DMA design. A further plus of the proposed methodology is its ability to identify many technically feasible solutions that can be subsequently economically assessed. The successful applications of the proposed methodology to a real case study, already tested by other authors, has proven its effectiveness for the DMA design in existing water distribution systems.     

Pressure Management in Water Distribution Systems Using a Self-Tuning Controller to Distribute the Available Potable Water with Equality

The rapid population growth of cities in developing countries (DC) make difficult to distribute the available potable water (PW) with equality. The distribution problem arises from an insufficient amount of PW and because cities water distribution systems (WDS) are not efficient. The novelty of this paper is a self-tuning controller (STC) proposed to manage, along the day, the pressure of water through the nodes of a WDS. It means, pressure management (PM) is proposed to control water levels (WLs) in householders tanks (HTs). The objective is to satisfy with equality the PW demand at different zones of a city forcing the flow of water by managing the pressure. The proposed STC performance is tested on the digital simulator developed to characterize the hydraulic operation of a WDS. The dynamic behaviour of the WDS is determined by the variation of the WL in the tanks of the WDS when water is supplied or extracted from them. The WDS of Mexico City is analysed and the proposed STC is applied to a simplified WDS. The results allow to conclude that the proposed STC could become a supporting tool for the decision making of WDS operators.     

Sustainable Water Supply and Demand Management in Semi-arid Regions: Optimizing Water Resources Allocation Based on RCPs Scenarios

Climate as one of the key factors in water resources management affects the amount of water in the hydrological cycle, which subsequently impacts the level of water availability. Considering the challenges that the South Alborz Region, Iran is currently facing in supplying water for various consumers; in this study, the climate change adaptation scenarios are investigated for sustainable water supply and demand. This study uses a procedure in which five different adaptation approaches, under RCPs scenarios, were established using the WEAP model to assess the impacts of various adaptation strategies on increasing the balance between water supply and demand over current and 2020s accounts. The findings suggest an imbalance between supply and demand in the current situation with the greatest imbalance in domestic use while the minimum in the industrial sector. The results of assessing adaptive scenarios show that various scenarios have different effects on balancing the water supply and demand by different consumers; on the other hand, the scenarios that directly affect domestic water demand have the greatest effect on minimizing the gap between supply and demand in the region; therefore, the options for decreasing the population demand along with diminishing the losses in the domestic water distribution network are the most effective alternatives for balancing supply and demand under all of the climate scenarios. The findings of this research indicate that adaptive management with the focus on restricting demand helps actively management of water resources in the regions with scarce water resources.

     

基于管网水力模型的独立计量分区优化

管网漏失和水质稳定性是影响供水安全的重要问题,科学合理的独立计量分区(Discrete Metering Area,DMA)管理,可以辅助漏失点定位,控制二次污染.根据北京市某区实际监测数据,开发了供水管网水力水质模型,并应用建立的模型针对该区分析了不同DMA方案的可行性,确定了优化的DMA模式.     

Water Security in an Uncertain Future: Contrasting Realities from an Availability-Demand Perspective

A better understanding of climate change impacts on water security beyond climate variability is of critical importance to tackle water vulnerabilities exacerbated by increasing extreme weather events. Thus, studies on water security in a changing climate help decision-makers to overcome existing political and socioeconomic challenges worldwide. In this study, future water security of two basins was assessed under climate change and demand scenarios by contrasting water demand with probabilistic levels of water availability to identify possible drivers of insecurity. The Guariroba and Jaguari basins are the main sources for supplying water to Campo Grande city and the São Paulo Metropolitan Region, respectively. The physically-based SWAT+?model was calibrated to simulate the basins’ hydrological response to three climate change scenarios from a CMIP6 multimodel ensemble: SSP2-4.5 (medium forcing), SSP3-7.0 (high forcing), and SSP5-8.5 (high forcing). The Guariroba basin already presented scarcity indices close to the security threshold in the baseline period. The imbalance between availability and demand was the main driver of water insecurity in this basin. Despite showing a low scarcity risk in the Jaguari basin in the baseline, this risk considerably increased in the future periods due to a decrease in precipitation. A reduction in water demand of 20% by 2070 was not sufficient to improve water security in both basins. These findings indicate that a lack of policies for adapting demand to a changing availability exacerbates hydrological droughts. More stringent measures to balance water availability and demand are critical for improving water security in an uncertain future.

     

Optimization of Investments in the Resilience of Water Distribution Systems Subject to Interruptions

In this paper, we propose an optimization model to support decisions related to the design of water distribution systems (WDS) that are subjected to interruptions caused by disruptive events, emphasizing their resilience capabilities, namely: absorption, adaptation, and recovery. Considering the exposure of WDS operation to random interruptions, we aim at minimizing the total investment considering the possibility of implementing actions that improve these capabilities, which can be put in place prior or posterior to the occurrence of a disruptive event. An application example is discussed as a way to understand the nature of the problem and to support the formulation of the proposed model. The results demonstrate the need to invest in resilient capacities adequate to each interruption probability associated to the disruptive scenarios, characterizing these considerations as of great importance to support managerial decisions, thus constituting a guideline for the allocation of investments before and/or after the occurrence of the event.

     

Penalty-Free Feasibility Boundary Convergent Multi-Objective Evolutionary Algorithm for the Optimization of Water Distribution Systems

This paper presents a new penalty-free multi-objective evolutionary approach (PFMOEA) for the optimization of water distribution systems (WDSs). The proposed approach utilizes pressure dependent analysis (PDA) to develop a multi-objective evolutionary search. PDA is able to simulate both normal and pressure deficient networks and provides the means to accurately and rapidly identify the feasible region of the solution space, effectively locating global or near global optimal solutions along its active constraint boundary. The significant advantage of this method over previous methods is that it eliminates the need for ad-hoc penalty functions, additional ??boundary search?? parameters, or special constraint handling procedures. Conceptually, the approach is downright straightforward and probably the simplest hitherto. The PFMOEA has been applied to several WDS benchmarks and its performance examined. It is demonstrated that the approach is highly robust and efficient in locating optimal solutions. Superior results in terms of the initial network construction cost and number of hydraulic simulations required were obtained. The improvements are demonstrated through comparisons with previously published solutions from the literature.     

洪河国家级自然保护区水资源需求研究

基于洪河国家级自然保护区水资源退化现状及湿地生态规律,认为洪河保护区水资源需求应从动态需求和静态需求两个方面来综合分析与计算。计算静态需求量时,视洪河保护区为一个平原水库,通过做出水位库容曲线,查出相对于原始状态保护区的静态需水量;计算动态需求量时,主要以湿地生态活跃期对水资源的动态需求过程为计算依据。通过分析计算,提出保护区维持现状和相对原始状态两种情况下的每年水资源动态需求量。