Drivers of non-revenue water: A cross-national analysis

Reducing water losses is seen as key to sustainable water management, but turns out to be challenging. This paper applies a panel data analysis with fixed effects to assess the major drivers of non-revenue water, some of which are under the control of utilities and some of which are not. The analysis finds that the most important drivers are population density per kilometer of network and type of distribution network, which are mostly resulting from urbanization patterns which are factors mostly out of the control of the utility. Yet, low opportunity costs of water losses and high repair costs of water losses have an important adverse effect on water loss reduction. We also found that the country environment in which the utility operates has an important impact on non-revenue water levels.     

确定性数学模型方法预测隧道涌水量研究

本文介绍了确定性数学模型预测隧道涌水量的常用方法,认为数值模拟方法是隧道涌水量预测的有效方法。并基于有限单元数值法对石太客运专线南梁隧道可能集中涌水区段进行了预测,结果表明其预测结果与实际情况基本吻合。     

给水管网水力模型的建立及应用

介绍了给水管网水力模型的建立、校核标准及思路,并以天津市滨海新区某新建园区内给水管网为对象,建立了水力模型,模拟管网在不同水力工况条件下的运行情况,对给水管网优化运行决策具有指导意义.     

An ARIMA-NARX hybrid model for forecasting urban water consumption (case study: Tehran metropolis)

ABSTRACT

In this research, an ARIMA-NARX (Autoregressive Integrated Moving Average-Nonlinear Auto-Regressive eXogenous) hybrid model is proposed to forecast daily Urban Water Consumption (UWC) for Tehran Metropolis. The linear and nonlinear component of the UWC was forecast by ARIMA as a linear forecasting model and the artificial neural network as a nonlinear forecasting model, respectively. An alternative hybrid model including sunshine hour in addition to the previous studies’ predictors (the minimum, maximum and average temperature, relative humidity and precipitation) was selected as the superior alternative model. Then, the performance of proposed model was compared with ARIMA and NARX models. The results showed that the hybrid model, which benefits from capability of both linear and nonlinear models, has a higher accuracy than the other two models in forecasting UWC. Therefore, the proposed hybrid model has better results in UWC forecasting and, as a consequence, better urban water reservoir management will be provided.     

含添加剂细水雾灭火模型及其应用

通过对细水雾的一维瞬间模型进行修改，建立了含添加剂细水雾灭火模型，并论述了该模型的实际应用，结合已有的实验条件对模型进行了验证。主要在于通过含添加剂细水雾灭火模型，提出了细水雾中添加剂灭火有效性的评价指标K，该模型还可对已安装的细水雾灭火系统的灭火有效性进行评价，因而具有较大的实际应用意义。     

GM（1,1）等维新息模型在某市需水量预测中的应用

用GM（1,1）等维新息模型对孟州市2010年,2015年,2020年的需水量进行了预测,得出需水量分别为7 759.6万m3,8 823.5万m3,9 015.3万m3。对预测结果的精度校验表明,模型的预测精度等级为一级,模型可靠、合理。     

An optimization model for water quantity and quality integrated management of an urban lake in a water deficient city

This paper presents an optimization model for water quantity and quality integrated management of an urban lake in a water deficient city. A representative water quantity and quality safeguard system served urban lake, including multi-source water supply facilities, recirculating water purification facilities and surplus water discharge facilities, is widely used in Chinese water deficient cities. Because it is complicated, any mismanagement will result in water quality deterioration, water waste and high operation cost. The presented model attempts to achieve the objectives of controlling water pollution, reducing economic cost and improving water utilization efficiency through an optimized operating water safeguard system. The model is applied to Qingjing Lake in Tianjin, China. Results show that the model plays a more positive role for water quantity and quality integrated management.     

螺杆式冷水机组稳态仿真模型的开发与应用

为预测螺杆式冷水机组在结构参数大范围变化时的运行性能,提出机组带经济器和不带经济器的稳态仿真模型。模型由压缩机、壳管式冷凝器、膨胀阀以及满液式蒸发器等一系列部件模型组成。结合顺序模块方法和连续替代方法实现了系统仿真。与4 台不带经济器和3台带经济器的冷水机组的实验数据相比,模型的预测结果误差在±10%以内。利用验证后的模型对机组中的经济器系统进行了参数敏感性分析,结果发现,机组带经济器运行后制冷量可明显提高,但只有当压缩机一级内压缩容积比大于某定值时,机组的COP才能明显提高。     

New lifeline multiscenario seismic risk techniques with a model application

This paper summarizes new lifeline seismic risk assessment techniques. These combine the advantages of deterministic (i.e., scenario-based) analyses with those of probabilistic (i.e., risk-based) analyses. Modifying the elegant work of Moghtaderizadeh and others, the new techniques are compatible with continuous component fragility models rather than being limited to artificial discrete dichotomous fragility models. Mathematical simplifications limit the number of events required so that the systemic consequences of those events can be examined in sufficient detail to permit comparison of alternative mitigations. These new techniques are demonstrated in terms of a model application to an urban water system in a highly seismic environment.     

供水管网系统用水模式确定与分析

用水模式制定是供水管网模型节点流量分配的重要步骤.主要阐述了城市供水管网系统用水模式制定的基本原则和方法,并对M市工程案例进行了示例分析,说明了用户分类过程中需注意的问题,提出采用GPRS机械远传表,可以实现数据的实时更新,保证了数据的可靠性,同时可为用水模式的制定打下基础,亦为供水管网模型精度的提高提供了有力支撑.     

A role for human reliability analysis (HRA) in preventing drinking water incidents and securing safe drinking water

The prevalence of water quality incidents and disease outbreaks suggests an imperative to analyse and understand the roles of operators and organisations in the water supply system. One means considered in this paper is through human reliability analysis (HRA). We classify the human errors contributing to 62 drinking water accidents occurring in affluent countries from 1974 to 2001; define the lifecycle of these incidents; and adapt Reason's ‘Swiss cheese’ model for drinking water safety. We discuss the role of HRA in human error reduction and drinking water safety and propose a future research agenda for human error reduction in the water sector.     

Climate change - An uncertainty factor in risk analysis of contaminated land

Metals frequently occur at contaminated sites, where their potential toxicity and persistence require risk assessments that consider possible long-term changes. Changes in climate are likely to affect the speciation, mobility, and risks associated with metals. This paper provides an example of how the climate effect can be inserted in a commonly used exposure model, and how the exposure then changes compared to present conditions. The comparison was made for cadmium (Cd) exposure to 4-year-old children at a highly contaminated iron and steel works site in southeastern Sweden. Both deterministic and probabilistic approaches (through probability bounds analysis, PBA) were used in the exposure assessment. Potential climate-sensitive variables were determined by a literature review. Although only six of the total 39 model variables were assumed to be sensitive to a change in climate (groundwater infiltration, hydraulic conductivity, soil moisture, soil:water distribution, and two bioconcentration factors), the total exposure was clearly affected. For example, by altering the climate-sensitive variables in the order of 15% to 20%, the deterministic estimate of exposure increased by 27%. Similarly, the PBA estimate of the reasonable maximum exposure (RME, defined as the upper bound of the 95th percentile) increased by almost 20%. This means that sites where the exposure in present conditions is determined to be slightly below guideline values may in the future exceed these guidelines, and risk management decisions could thus be affected. The PBA, however, showed that there is also a possibility of lower exposure levels, which means that the changes assumed for the climate-sensitive variables increase the total uncertainty in the probabilistic calculations. This highlights the importance of considering climate as a factor in the characterization of input data to exposure assessments at contaminated sites. The variable with the strongest influence on the result was the soil:water distribution coefficient (Kd).     

Investigating effects of bromide ions on trihalomethanes and developing model for predicting bromodichloromethane in drinking water

Chlorination for drinking water can form brominated trihalomethanes (THMs) in the presence of bromide ions. Recent studies have reported that bromodichloromethane (BDCM) has a stronger association with stillbirths and neural tube defects than other THMs species. In this paper, the results of an experimental investigation into the factors forming THMs in the presence of bromide ions are presented. The experiments were conducted using synthetic water samples with different characteristics (e.g., pH, temperature, dissolve organic content). Different combinations of these characteristics were considered in the experimental program. The results showed that increased bromide ion concentrations led to increases in the formation of total THMs, with higher BDCM and dibromochloromethane (DBCM), and lower chloroform formation. By increasing the pH from 6 to 8.5, increased chloroform and decreased BDCM and DBCM formation were observed. Higher bromide ions to chlorine ratios increased BDCM and DBCM and decreased chloroform formation, while higher temperatures increased BDCM, DBCM and chloroform formation. In most cases, bromoform (CHBr₃) concentrations were found to be below the detection limit. Significant factors influencing BDCM formation were identified using a statistical analysis. A model for BDCM formation was estimated from 44 experiments and statistical adequacy was assessed using appropriate diagnostics, including residual plots and an R² of 0.97. The model was validated using external data from 17 water supply systems in Newfoundland, Canada. The predictive performance of the model was found to be excellent, and the resulting model could be used to predict BDCM formation in drinking water and to perform risk-cost balance analyses for best management practices.     

Model development for predicting changes in DBP exposure concentrations during indoor handling of tap water

Disinfection by-products (DBPs) in municipal drinking water are a matter of concern because of their possible risks to human health. Risk assessment studies often use measurements of DBPs in water distribution systems, whereas populations are typically exposed to the indoor tap water. Further to this, consumers often employ several indoor strategies to handle tap water (e.g., storing in a refrigerator, boiling, filtering, etc.) prior to use. The indoor handling of municipal water may have implications on DBPs' exposure assessment. This study investigates and develops models to predict the effects of various indoor handling strategies on trihalomethanes (THMs) and haloacetic acids (HAAs). Linear and nonlinear models are developed to predict changes in THM and HAA concentrations due to various indoor water manipulation strategies. The models are capable of assessing representative exposure concentrations of THMs and HAAs as a result of indoor handling, which might be useful in gaining a better understanding of exposure and risks from DBPs in municipal drinking water.     

城市水资源优化配置模型研究

结合某市新区发展特性,建立了城市分质供水水资源优化配置数学模型,对新区中水、雨水与自来水等水资源进行了优化配置仿真计算。结果表明,水资源的综合优化配置有利于社会经济的协调发展,实现水资源的可持续利用,具有良好的经济、社会和环境效益。     

纯净水水质及生产企业风险评价系统

本文把层次分析法和灰色分析方法结合起来用于纯净水水质风险评价,用最差判别法对纯净水生产企业进行评价,并用Visual Basic计算机语言开发设计了一个水质风险评价系统。结果显示所给组合方法不仅可以判断纯净水是否符合标准,还可以评估符合标准的纯净水存在的潜在风险,最差方法在生产企业水质风险评价过程中具有一定实用性。所构建的纯净水水质风险评价系统,可以为纯净水水质监管部门提供方便的服务,自动生成的图形分析结果可以为监管部门提供直观、有效的数据。     

A semi-implicit finite element model for natural water bodies

In this work, a semi-implicit model, applied to the shallow water equations, is developed for natural water bodies. In the proposed model, the shallow water equations are integrated in the vertical direction, finite elements are employed in the spatial discretization, and finite differences in the time discretization. The model is based on the uncoupling of the governing equations, in which the expressions of the velocity components, obtained explicitly from the discretized momentum equations, are substituted in the continuity equation. Therefore, there is an uncoupling of the solution; initially the continuity equation is solved, and, in the sequence, the momentum equations are solved. Yet, this uncoupling produces a significant reduction in the number of equations of the resulting systems, when compared to standard coupled systems. This reduction improves substantially the computer performance.     

三维渗流模型在李楼铁矿矿坑涌水量预测中的应用

李楼铁矿赋存于新太古界霍邱群周集组片岩、片麻岩及白云石大理岩中,矿体及围岩构造裂隙带,为矿床水的储存与运移通道;矿体上覆周集组风化裂隙含水层、青白口系风化裂隙含水层与第四系孔隙含水层,构成一个分布范围大、厚度大、透水性较差、富水性较弱含水体,为矿坑水的充水来源。矿山开采于深部-200m疏干排水时,地下水向排水点汇聚,第四系底部薄含水层承压水压力迅速释放并向四周扩展,上覆第四系孔隙水越流补给,垂向上存在地下水水头梯度,地下水流场呈现三维空间流场。文章在上述水文地质条件认识的基础上,利用地下水三维观测系统取得的长期动态观测资料和放水试验资料,建立三维流数学模型预测矿坑涌水量,并提出了矿山防治水建议,指导矿山建设。     

径向基函数神经网络预测城市用水量模型及应用

以城市用水人口和城市生产总值作为输入向量,年用水量数据作为目标向量,建立了径向基函数神经网络并对城市用水量进行预测。采用不同的扩展速度,预测误差不同。当扩展速度spread=1时,预测数据与实际数据的相对误差均小于0.05%,取得了很好的预测效果,说明采用径向基函数神经网络模型预测城市用水量的方法是可行的。     

基于AHFO技术的毛细水运移模型验证试验研究

为了验证常用的描述毛细水运移模型的准确性,设计了室内模型试验,采用主动加热光纤法(简称AHFO)对砂土模型中的毛细水运移进行了测试。根据测试结果,分析了毛细水入渗模型Green-Ampt模型、Terzaghi毛细水上升模型和毛细水最大上升高度预测模型Lane模型、Peck模型的特点和预测精度。试验分析结果表明:对于砂性土,毛细水上升过程可以分为两个阶段,第一阶段(约前50 h),Green-Ampt模型和Terzaghi毛细水上升模型预测的毛细水上升高度值均低于实测值,Terzaghi模型拟合精度高于Green-Ampt模型;第二阶段(约50h后),Green-Ampt模型和Terzaghi模型预测值均高于实测值,且Green-Ampt模型拟合精度高于Terzaghi模型。这两个模型预测精度随时间的变化现象是与其所用的假设条件和土体物理性质变化有关。Peck模型的误差低于Lane模型,为2.60 cm,而Lane模型由于只考虑了有效粒径D10,误差高达8.58 cm。利用Green-Ampt模型可反演土的饱和渗透系数与湿润锋处基质吸力。研究成果为常用毛细水运移模型选择和误差分析提供了实测依据。