Results of an urban water distribution network performance evaluation attempt in Greece

The need for efficient water resources management is currently more pressing than ever, considering population growth and increased reliability requirements, under climate change conditions. On average, one-third of the total water abstracted for urban uses is being lost due to leaks and breaks occurring in water distribution networks. This means that significant amounts of water and revenues are being lost, forcing water utilities to consider developing effective water loss and Non-Revenue Water reduction strategies. Additionally, all water utilities operating in EU countries should, by the end of 2010, develop and implement appropriate water pricing policies that will guarantee the recovery of the full cost of the water being used. This strict obligation makes the reduction of water losses an even more urgent goal that the water utilities have to achieve. The first step towards all the above-mentioned goals is to safely evaluate the performance level of the water network. Thus, the IWA Task Forces on Water Losses and Performance Indicators (PIs) developed specific tools (e.g., the standard international water balance and various PIs), to help water utilities use a common language that will assist know-how and experience exchange through an effective benchmarking process. The paper presents the results of using the above-mentioned IWA tools, in the case of the Larisa city water distribution network in Greece. This is the first time that such an attempt has taken place in Greece. During this process, the problems faced and the ways to tackle them are analyzed, focusing on the role of key factors that had to do with local conditions. Larisa's results are compared to data available from similar cases. Sensitivity analysis was used to check the impact of the variables' uncertainty to the results. Finally, water loss reduction measures are proposed towards an effective pressure management strategy and a proactive pipe maintenance policy based on safely estimating the pipes' optimum replacement time.     

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.     

Robust optimization of valve management to improve water quality in WDNs under demand uncertainty

ABSTRACT

Water quality deterioration in water distribution networks can be associated with high water residence time in the network. To this end, some previous studies have proposed optimization procedures for valve management. However, these studies generally come up with operational configurations assuming deterministic user demand patterns that may never occur in reality. In consequence, the proposed solutions may not be effective for improving water quality or do not comply with pressure constraints if different demand patterns are observed. This study proposes a methodology to determine robust configurations of the valves to keep water residence time at acceptable levels regardless of the variability in demand patterns. The methodology is tested on four different distribution systems of varying topology and size. Results show the importance of executing robust – instead of deterministic, optimization to find valve configurations that guarantee the performance of the networks in terms of hydraulics and water quality.     

Assessment of predictive uncertainty within the framework of water demand forecasting using the Model Conditional Processor (MCP)

This paper presents an application of the Model Conditional Processor (MCP), originally proposed by Todini (2008) within the hydrological framework, to assess the predictive uncertainty in water demand forecasting related to water distribution systems. The MCP enables us to assess the probability distribution of the future water demand conditional on the forecasts provided by two or more deterministic forecasting models. In the numerical application described here, where two years of hourly water demand data for a town in northern Italy are considered, two forecasting models are applied in order to forecast hourly water demands from 1 to 24 hours ahead: the first model has a modular structure comprising a periodic component which reflects the long-term effects and a persistence component which represents the short-term memory of the process; the latter is based on neural networks. The results highlight the effectiveness of the approach, provided that the data set used for the MCP parameterization is properly selected so as to be actually representative of the accuracy of the real-time water demand forecasting models.     

A decision support tool for sustainable planning of urban water systems: Presenting the Dynamic Urban Water Simulation Model

Population growth, urbanisation and climate change represent significant pressures on urban water resources, requiring water managers to consider a wider array of management options that account for economic, social and environmental factors. The Dynamic Urban Water Simulation Model (DUWSiM) developed in this study links urban water balance concepts with the land use dynamics model MOLAND and the climate model LARS-WG, providing a platform for long term planning of urban water supply and water demand by analysing the effects of urbanisation scenarios and climatic changes on the urban water cycle. Based on potential urbanisation scenarios and their effects on a city's water cycle, DUWSiM provides the functionality for assessing the feasibility of centralised and decentralised water supply and water demand management options based on forecasted water demand, stormwater and wastewater generation, whole life cost and energy and potential for water recycling. DUWSiM has been tested using data from Dublin, the capital of Ireland, and it has been shown that the model is able to satisfactorily predict water demand and stormwater runoff.     

浅谈小城镇用水量的计算

探讨了小城镇给水工程规划设计中各种用水定额的取值及其管段流量的计算问题，从小城镇的实际出发，并展望了小城镇的发展未来。给全山西小城镇的具体情况，论述了综合生活用水量、工业企业生产用水量、消防用水量、浇洒道路和绿地用水量、未预见用水量及管网漏失水量的取值依据及管段流量的计算方法。经分析讨论，提出了适合小城镇的用水定额和管段流量的计算方法。     

高层建筑给水系统分析

给水方式的选择关系到整个高层建筑给水系统的供水可靠性、工程投资、运行费用、维护管理及使用效果。文章对给水方式的方案比较和优化选择作了较为详细的分析,分析了高位水箱供水方式、气压罐供水方式和变频调速水泵供水方式,并列举了竖向串联水箱的应用实例。     

Investigation of water quality in combined recycled water and stormwater systems

Integrated Urban Water Management (IUWM) approach is an important strategy for urban water utilities to improve water security and system resilience. This study proposes a novel approach to combine recycled water and stormwater. This novel mixing method of capturing and treating stormwater at various locations along the recycled water pipeline and injecting treated stormwater in to the recycled water pipe line is unknown to have been practiced anywhere in the world. Water quality control of combined water is a vital factor for the safe use, as mixing percentage of stormwater is decided based on availability. A method to determine the water quality before mixing is required. Therefore, this paper investigates the appropriateness of the mass balance method to compute combined water quality and proposes a guideline for water quality of combined water.     

Dynamics of water use in Scotland

This paper uses a variety of data sources and methodologies to construct business as usual (BAU) water‐use scenarios for the Water Framework Directive (WFD) characterisation report, a key preliminary benchmarking requirement for member states. The paper addresses the most significant water‐use sectors in Scotland over the period 2001–2015. In terms of volumetric use, our figures are dominated by the demands of electricity generation. The next highest demands come from fish farming/aquaculture, which is mostly direct abstraction. Various industrial uses are estimated to be associated with significant volumetric uses (specifically electrical and engineering, fibres and food and drink). Because of structural changes in farm support, agriculture is the only sector showing a decline. Household demand is also a highly significant use and we are able to specify the public/private breakdown of demand.     

The economic impact of restricted water supply: a computable general equilibrium analysis

Water problems are typically studied at the level of the river catchment. About 70% of all water is used for agriculture, and agricultural products are traded internationally. A full understanding of water use is impossible without understanding the international market for food and related products, such as textiles. The water embedded in commodities is called virtual water. Based on a general equilibrium model, we offer a method for investigating the role of water resources and water scarcity in the context of international trade. We run five alternative scenarios, analyzing the effects of water scarcity due to reduced availability of groundwater. This can be a consequence of physical constraints, and of policies curbing water demand. Four scenarios are based on a "market solution", where water owners can capitalize their water rent or taxes are recycled. In the fifth "non-market" scenario, this is not the case; supply restrictions imply productivity losses. Restrictions in water supply would shift trade patterns of agriculture and virtual water. These shifts are larger if the restriction is larger, and if the use of water in production is more rigid. Welfare losses are substantially larger in the non-market situation. Water-constrained agricultural producers lose, but unconstrained agricultural produces gain; industry gains as well. As a result, there are regional winners and losers from water supply constraints. Because of the current distortions of agricultural markets, water supply constraints could improve allocative efficiency; this welfare gain may more than offset the welfare losses due to the resource constraint.     

Inventory of water management practices in Harare, Zimbabwe

Lake Chivero, in Zimbabwe, is the major water supply source for the greater Harare area. This paper looks at the sustainability of current practices of the urban water cycle in relation to water quantity and quality management in the Chivero catchment. Data on population, water supply, water and wastewater treatment and river flows were obtained from urban councils and government departments. The data were used to assess water consumption, wastewater generation, treatment and disposal practices, river flow trends, raw water abstractions and water demand patterns. The results showed that the current situation is not sustainable as water quantity in the catchment will soon be a problem at current levels of consumption while water quality is already a problem, especially with regard to nutrient levels. Water and nutrient management strategies, which include water use efficiency, treatment and water recycling and nutrient reuse in controlled urban agriculture, are recommended as matters of urgency.     

福州市水资源供需平衡的对策

水资源规划的核心是水资源平衡,水资源平衡是需求和供给的平衡,需水量预测包括工业、农业、城镇生活和河道生态需水量四个部分。通过分析用水统计数据,研究用水结构特点,进行需水量预测,提出水资源供需平衡规划及对策。     

Development of small district adjustment based on public water demand to decrease the municipal water supply load

This research microscopically estimates the spatial distribution of water demand and aims to use this to improve the existing zone system. So, this study used geographic information system (GIS) to predict the spatial distribution of water demand according to building unit by applying the basic unit of water use by purpose. Based on the results, the buildings were then grouped into blocks to produce a methodology for controlling small districts using a microscopic approach to decrease the water supply load based on water demand per block. Finally, verification was conducted by quantitatively evaluating the load-decreasing effect through the application of the above methodology. We evaluated efficiency and verified the study's methodology by analysing urban areas that had been Manhattanized and densificated, finding a reduction of approximately 16.7%. The possibility of expanding the study's scope to medium and large districts was suggested.     

Application of modified complementary reservoir approach in analysis of water distribution networks under pressure-deficient conditions

Hydraulic simulation models which simulate water distribution systems in different operating conditions are essential tools to evaluate network reliability. Simulation models found in most commercial software are not effectively capable of analyzing demand nodes under critical conditions such as fire-fighting demand or network pipe breakage. In the current study, a combination of hydraulic model and complementary reservoir solution (CRS) method is used for solving network's problems in critical conditions for both series-looped networks and a part of water network in Ilam city (Iran). Obtained results show that CRS provide more than actual need on the demand node for some reservoir total pressure heads. Thus, two modified versions of CRS method are proposed to deal with failures of CRS in such cases. Obtained results demonstrate improved efficiency in the combined model for analyzing networks in abnormal conditions.     

从管网供水漏失率分析乡镇供水现状

分析了目前乡镇供水回收率普遍偏低的主要原因：供水主管线老化，深井水硬度较大造成管道严重结垢、渗漏，年久失修；规范中乡镇供水标准制定偏高，与实际使用情况不符，造成供水量与用水量的不平衡；乡镇水厂管理水平低，出现以小带大的管线设置，增加了水头损失，降低了供水压力。提出了加强乡镇技术管理水平和对老管线进行测漏排查的建议，以期为合理规划乡镇用水量标准提供参考依据。     

Network structure,complexity, and adaptation in water resource systems

Infrastructure systems are often complex. Many have both natural and built components. For such systems, including water resource networks, resilience is a common policy goal. In the formalised study of complex systems, the structure and function of networks can contribute directly to system resilience. One branch of complex systems studies, network science, describes how connectivity between individual components can explain some system-wide properties of growth and reliability. Water resource systems analysis has only begun to apply techniques from network theory and complexity science to assess adaptability and resilience. We present an analysis of connectivity in a network model of California's water infrastructure system using several network science techniques. Results indicate that nodes in California's water system are clustered but without scale-free properties. The network originates from a mixture of top-down (centralised) and bottom-up (dispersed interactions of parties) planning. This structure provides managers greater flexibility to use local and distant water sources. We use the analysis to illustrate how several disciplinary notions of resilience apply to civil infrastructure planning. We also explore how adaptability, not just complexity, influences resilience in planning. Creating systems that can respond to future changes must be an important policy goal in planning civil infrastructure.     

Environmental Kuznets curve and the water footprint: an empirical analysis

Water is an essential element for life, playing an important role in economic development, although it is threatened by negative externalities that do not make it available for everyone. The main purpose of this article is to offer insightful empirical evidence of the nexus between economic growth and water usage. In this article we investigate the Environmental Kuznets Curve (EKC) hypothesis using a country's water footprint as an indicator of water impact. Using linear and nonlinear models we estimate, through the ordinary least square, the relationship between water impact and gross national income (GNI) per capita for 94 Countries. Our study shows an N‐shape curve, which does not confirm the EKC hypothesis, both for the relationship between Water Footprint per capita and GNI per capita and Grey Water Footprint per capita and GNI per capita. From this results, a number of recommendations can be provided to strengthen the water resources policies and management.     

浅谈优化城镇给水厂的运行和管理

提出了优化城镇给水厂运行和管理的概念，概括了优化的三个主要方面，就如何在运行和管理城镇给水厂的过程中提高水资源利用效率，节约水资源提出了相应的措施，并且，从给水厂中能源消耗的主要途径分析了节约能源和降低消耗的可行方法。