Locating of Probabilistic Leakage Areas in Water Distribution Networks by a Calibration Method Using the Imperialist Competitive Algorithm

Water Resources Management - Leakages in water distribution networks (WDNs), in addition to water loss, causes more problems such as water pollution and land subsidence. In this paper, a new method...     

Calibration of Design Models for Leakage Management of Water Distribution Networks

Water Resources Management - Water losses in urban water distribution networks (WDN) accelerate the deterioration of such infrastructures. The enhanced hydraulic modelling provides a...     

Modeling of Drinking Water Distribution Networks Using Stochastic Demand

Residential water demand is one of the most difficult parameters to determine when modeling drinking water distribution networks. It has been proven to be a stochastic process that can be characterized as a series of rectangular pulses with a set intensity, duration and frequency. These parameters can be determined using stochastic models such as the Neyman-Scott Rectangular Pulse (NSRP) model. The NSRP model is based on the solution of a non-linear optimization problem. This solution involves theoretical moments that represent the synthetic demand series (equiprobable) and the observed moments (field measurements) that statistically establish the measured demand series. The NSRP model has been applied for residential demand, and the results have been published. However, this model has not been validated for a real distribution network or compared with traditional methods. The present study compared the results of synthetic stochastic demand series, which were calculated using the NSRP model, applied to the determination of pressures, flow rates and leaks; to the results obtained using traditional simulation methods, which use the curve of hourly variation in demand, and to actual pressure and flow rate measurements. The Humaya sector of Culiacan, Sinaloa, Mexico, was used as the study area.     

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.     

Optimization of Sewer Networks Using an Adaptive Genetic Algorithm

This work aims at introducing an optimization model to design sewer networks. The approach specially focuses on handling the nonlinear and discrete constraints of the problem. For this purpose, an adaptive genetic algorithm is developed so that every chromosome, consisting of sewer diameters and slopes and pump indicators, is a feasible design. The binary chromosomes are freely generated and then decoded to feasible design alternatives following a sequential design-analysis algorithm. The adaptive decoding strategy is set up based on the open channel hydraulics and sewer design criteria. Through the proposed method, all the sewer system??s constraints are systematically satisfied. Consequently, there is neither need to discard or repair infeasible chromosomes nor to apply penalty factors to the cost function. A benchmark sewer network from the literature is considered to be designed using the proposed approach. The obtained results are then discussed and compared with the previous works. It is found that the adaptive constraint handling method computationally makes the optimization more efficient in terms of speed and reliability.     

Entropy-Based Sensor Placement Optimization for Waterloss Detection in Water Distribution Networks

The work presented herein addresses the problem of sensor placement optimization in urban water distribution networks by use of an entropy-based approach, for the purpose of efficient and economically viable waterloss incident detection. The proposed method is applicable to longitudinal rather than spatial sensing, thus to devices such as acoustic, pressure, or flow sensors acting on pipe segments. The method utilizes the maximality, subadditivity and equivocation properties of entropy, coupled with a statistical definition of the probability of sensing within a pipe segment, to assign an entropy metric to each pipe segment and subsequently optimize the location of sensors in the network based on maximizing the total entropy in the network. The method proposed is a greedy-search heuristic.     

Leakage Detection Using Smart Water System: Combination of Water Balance and Automated Minimum Night Flow

This paper presents a methodology for the application of the Smart Water technology to detect water leakage. This methodology consists in the use of the traditional water balance method together with the minimum night flow approach. This procedure has been applied to a large-scale pilot project conducted at the Scientific Campus of the University of Lille, which is the size of a small town. The water network of the campus is monitored by a set of sensors that record and transmit, in real-time, the hydraulic parameters of the water system. Analysis of real-time data has allowed the verification of water balance and the estimation of water losses level in the network. The paper presents an improvement of the application of the minimum night flow method, which is based on the determination of flow thresholds. A leak alarm is generated if the night flow exceeds the thresholds. This data analysis methodology provides the capability to detect the pipe bursts quickly, thereby reducing the runtime of leakage. The application of the improved method allowed the detection of 25 unreported leaks and decreased the Non-Revenue Water (NRW) level by 36%.     

GIS局放耦合器密封性现场检测及气体泄漏允许值的探讨

鉴于局放耦合器部位SF6气体泄漏量的大小直接影响GIS设备的长期安全稳定运行,介绍了某电站局放耦合器现场气体检漏检测方法及泄漏量允许值的计算方法,提出了制定精确规范的局放耦合器现场检漏方法以及泄漏量允许值标准的建议。     

Multiobjective Calibration of Reservoir Water Quality Modeling Using Multiobjective Particle Swarm Optimization (MOPSO)

Water resource management encounters large variety of multi objective problems that require powerful optimization tools in order to fully characterize the existing tradeoffs between various objectives that can be minimizing difference between forecasted physical, chemical, and biological behaviors of model and measured data. Calibration of complex water quality models for river and reservoir systems may include conflicting objectives addressed by various combinations of interacting calibration parameters. Calibration of the two dimensional CE-QUAL-W2 water quality and hydrodynamic model is an excellent example where the model must be calibrated for both hydrodynamic and water quality behavior. The aim of the present study is to show how multiobjective particle swarm optimization (MOPSO) can be implemented for automatic calibration of water quality and hydrodynamic parameters of a 2-dimensional, hydrodynamic, and water quality models (CEQUAL-W2) to predict physical, chemical, and biological behaviors of a water body, and then focus on a relevant case study. So MOPSO is utilized to generate Pareto optimal solutions for two conflicting calibration objectives. A combined measure of thermal and reservoir water level is considered as the first calibration objective. The second objective is formulated to forecast the best physical, chemical, and biological behavior of the model. Realizing the strong interactions between water quality and hydrodynamic issues of water bodies and their dependencies on the same set of calibration parameters, the proposed multiobjective approach may provide a wide version of all possible calibration solutions for better decision making to select best solution from pareto front.     

农村饮水安全工程供水水量漏失问题分析及对策

供水管网渗漏是农村饮水安全工程水量损失的主要因素,供水管网漏失不仅对供水企业造成了经济损失,也造成了水资源的巨大浪费。导致供水渗漏的原因很多,本文通过对农村饮水安全工程运行过程中供水管网水量漏失原因进行分析,提出针对工程管理过程中水量漏失问题的对策,以保障工程正常运行。     

Optimal Design of Water Distribution Networks Considering Fuzzy Randomness of Demands Using Cross Entropy Optimization

This paper presents cross entropy (CE) optimization for optimal design of water distribution networks (WDN) under demand uncertainty. In design of WDNs, it is desired to achieve a minimum cost WDN that provides higher reliability in meeting the demands. To achieve these goals, an optimization model is formulated for design of WDNs with an objective of minimizing the total cost of WDN subject to meeting the nodal demands at a specified system reliability, mass conservation and other physical constraints. The uncertainty in future water demands is modeled using the theory of fuzzy random variable (FRV). The water demand at each node is assumed to be following a normal distribution with a fuzzy mean, and 10 % (or 20 %) of the fuzzy mean as its standard deviation. The water demand is represented as a triangular fuzzy number with the random demand as its kernel, and the interval of ±5 % (or ±10 %) variation of the random demand as its support for two scenarios. The fuzzy random system reliability (R) of WDNs is defined on the basis of necessity measure to assess system performance under fuzzy random demands and crisp head requirements. The latin hypercube sampling method is adopted for sampling of uncertain demands. The methodology is applied to two WDNs, and optimization models are solved through cross entropy optimization for different levels of reliability, and generated tradeoffs between the cost and R. On comparing the solutions obtained with the proposed methodology with earlier reported solutions, it is noted that the proposed method is very effective in producing robust optimal solutions. On analyzing the tradeoffs between reliability and costs, the results show that negligence of uncertainty can lead to under design of the WDNs, and the cost increases steeply at higher levels of reliability. The results of the two case studies demonstrate that the presented CE based methodology is effective for fuzzy-probabilistic design of WDNs.     

Watershed Approach for the Protection of Drinking Water Supplies in Central Illinois

A number of communities in Central Illinois that depend on surface water supplies for their drinking water have been experiencing water quality problems in recent years. Since the dominant land use in the region is agriculture, most of the water quality problems are generally attributed to changes in agricultural practices, especially application of fertilizers and pesticides. The most pressing drinking water quality problem in Central Illinois is high nitrate concentration. The maximum contaminant level (MCL) for nitrate in drinking water is set at10 milligrams per liter. A Technical Advisory Committee developed a set of recommendations on how to implement watershed-based solutions to the water quality problem in Central Illinois based on the results of several hydrologic and water quality studies.     

Toward Improved Calibration of SWAT Using Season-Based Multi-Objective Optimization: a Case Study in the Jinjiang Basin in Southeastern China

Calibration is an important step in most hydrological modeling processes because it helps produce reasonable results. This study aims to investigate the seasonal sensitivity of streamflow parameters and to evaluate the ability of a season-based multi-objective approach to calibrate the Soil and Water Assessment Tool (SWAT) model. The primary goal was achieved through an integrated approach. A variance-based global sensitivity technique, Sobol’ method, was used to evaluate the seasonal sensitivity of streamflow parameters. For the multi-objective approach, three objective functions were considered: the Nash–Sutcliffe efficiency, Nash–Sutcliffe efficiency of logarithmic transformed discharge, and relative bias. The model performances of the season-based multi-objective approach MOO(II), based on these functions and flow duration curves during wet and dry seasons, were compared to three other methods: SOO(I), a conventional single-objective approach to the entire series; SOO(II), a season-based single-objective approach; and MOO(I), a multi-objective approach for the entire series. The four methods were assessed using the SWAT model to predict daily discharge in the Jinjiang basin in southeastern China. The results showed that sensitivity of model parameters varied between the wet and dry seasons. The seasonal calibration approaches, MOO(II) and SOO(II), showed significantly better simulation performances during the dry season while the multi-objective approaches produced more accurate simulations of different aspects of the hydrograph, including peak and low flows and overall water balance, compared to the single-objective methods. MOO(II) captured the seasonal variation of hydrological processes best, compared to the other methods, and the parameter values it identified demonstrated significant seasonal variations.     

某大坝渗漏原因分析及治理措施探讨

某水库大坝高水位时背水坡出现渗水点,渗流量突增等现象,采用地质勘察、测压管水位监测、地球物理勘探3种方法进行渗漏原因探测分析,得到大坝的渗漏区域主要在右坝肩位置和坝体上部;采用灌浆方案处理后大坝渗漏问题彻底解决,研究成果可为类似工程提供参考.     

基于差分进化算法的水位流量关系曲线优化率定

针对水位流量关系常规模型率定时中高水、低水无法兼顾的问题,该文采用一类保凸保单调函数的新水位流量关系模型[1],可以有效解决这一不足,而且易于水位流量关系曲线的自动优化率定。同时采用差分进化算法求解该模型,实例表明,该模型可以更好地拟合水位流量关系曲线,避免了人工率定的任意性并降低了人工操作的复杂性。     

Robust Parameter Set Selection for a Hydrodynamic Model Based on Multi-Site Calibration Using Multi-Objective Optimization and Minimax Regret Approach

A robust parameter set (ROPS) selection method for a hydrodynamic flow model was proposed based on the multi-site calibration by combining multi-objective optimization with the minimax regret approach (MRA). The multi-site calibration was defined by a multi-objective optimization problem for which individual objective functions were used to measure errors at each site. In the hydrodynamic model, coefficients of power functions that show the changing relationships between Manning’s roughness and discharge in each sub-reach were optimized by minimizing the residuals of multiple sites. Different combinations of weights were assigned to sites in the application of an aggregation approach to solve the multi-objective function, and the corresponding Pareto optimal parameter sets were assumed as the ROPS candidates. All performance measures to individual Pareto optimal parameter sets were calculated and the ROPS was determined using MRA. The set which has the lowest maximum regret obtained by averaging the results from calibration and validation was determined as the only ROPS. It was found that the estimated variable roughness and the corresponding computed water levels varied considerably depending on the weights assigned to sites. Using the proposed method, the task to assign proper weights on multiple sites can be easily achieved for multi-site calibration problems. This study provides a multi-criteria decision making method to choose a ROPS that has the lowest potential regret among various alternatives for hydrologic and hydraulic models.     

水工闸门启闭力的检测与分析

文章通过工程检测实例,介绍了水工闸门启闭力检测方法;根据检测数据,反演计算出在设计情况下闸门的启闭力特性,为闸门运行的安全提供了可靠的科学依据。     

径流曲线法参数率定优化方法与应用研究

为提高径流曲线法参数率定的精度,增强径流曲线法的适用性,基于分析前期影响雨量、土壤类型、土地利用类型等影响因素,提出参数CN值率定的优化方法。优化方法结合历史水文资料,通过建立目标函数及约束条件,实现参数快速准确率定。以济南市章丘区大站水库流域为例进行参数优化方法的应用研究。结果表明:计算结果相对误差小于10%,相较于传统查表法,该方法的适用性更强,结果精度更高。     

EH4电磁成像系统在水库漏水探测中的应用

将EH4电磁成像系统应用于岩溶埋深较深的河湾水库漏水的勘察,结合地质及钻探资料对比分析,宏观上查明河湾地块深部漏水通道、地质构造及岩性分界,为该电站河湾地块漏水点的工程的整治和修复方案的制定提供可靠的依据,是现代地球物理方法发挥作用的一个广阔领域。     

综合探测方法在某堤防渗漏强弱分区中的应用

国内外堤防渗漏探测的物探方法多侧重于渗漏点的探寻与查找,较少开展划分堤防渗漏强弱区段的探测。在有限的资源条件下,为对堤防进行评估和治理,往往需查明其渗漏的强弱,有针对性的采取措施。对于此类问题的解决,单一的探测方法往往难以达到预期的效果。为解决此类问题,文章结合在某堤防渗漏探测实例实践中,尝试采用联合剖面法与伪随机流场法相结合的综合探测方法开展对堤防渗漏的探测,并通过2种探测方法结果的相互印证、联合分析,较为准确地区分了探测堤段各部分的渗漏强弱。实践证明,联合剖面法与伪随机流场法相结合的综合探测方法在堤防渗漏强弱探测中可行、有效,可作为今后此类问题的解决方法。