Environmental Problems in an Urbanizing World

Intermittent water supplies (IWS), in which water is provided through pipes for only limited durations, serve at least 300 million people around the world. However, providing water intermittently can compromise water quality in the distribution system. In IWS systems, the pipes do not supply water for periods of time, supply periods are shortened, and pipes experience regular flow restarting and draining. These unique behaviors affect distribution system water quality in ways that are different than during normal operations in continuous water supplies (CWS). A better understanding of the influence of IWS on mechanisms causing contamination can help lead to incremental steps that protect water quality and minimize health risks. This review examines the status and nature of IWS practices throughout the world, the evidence of the effect of IWS on water quality, and how the typical contexts in which IWS systems often exist—low-income countries with under-resourced utilities and inadequate sanitation infrastr...

Intermittent Water Supply: Prevalence, Practice, and Microbial Water Quality

Water quality assessment at the watershed scale requires not only an investigation of water pollution and the recognition of main pollution factors, but also the identification of polluted risky regions resulted in polluted surrounding river sections. To realize this objective, we collected water samplings from 67 sampling sites in the Honghe River watershed of China with Grid GIS method to analyze six parameters including dissolved oxygen (DO), ammonia nitrogen (NH3-N), nitrate nitrogen (NO3-N), nitrite nitrogen (NO2-N), total nitrogen (TN) and total phosphorus (TP). Single factor pollution index and comprehensive pollution index were adopted to explore main water pollutants and evaluate water quality pollution level. Based on two evaluate methods, Geo-statistical analysis and Geographical Information System (GIS) were used to visualize the spatial pollution characteristics and identifying potential polluted risky regions. The results indicated that the general water quality in the watershed has been exposed to various pollutants, in which TP, NO2-N and TN were the main pollutants and seriously exceeded the standard of Category III. The zones of TP, TN, DO, NO2-N and NH3-N pollution covered 99.07%, 62.22%, 59.72%, 37.34% and 13.82% of the watershed respectively, and they were from medium to serious polluted. 83.27% of the watershed in total was polluted by comprehensive pollutants. These conclusions may provide useful and effective information for watershed water pollution control and management.

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Assessment of water quality and identification of polluted risky regions based on field observations & GIS in the Honghe River watershed, China.

Drinking water distribution systems throughout the world supply water intermittently, leaving pipes without pressure between supply cycles. Understanding the multiple mechanisms that affect contamination in these intermittent water supplies (IWS) can be used to develop strategies to improve water quality. To study these effects, we tested water quality in an IWS system with infrequent and short water delivery periods in Hubli-Dharwad, India. We continuously measured pressure and physicochemical parameters and periodically collected grab samples to test for total coliform and E. coli throughout supply cycles at 11 sites. When the supply was first turned on, water with elevated turbidity and high concentrations of indicator bacteria was flushed out of pipes. At low pressures ( 17 psi.

Mechanisms affecting water quality in an intermittent piped water supply.

A GIS-based decision support system for regional eco-security assessment and its application on the Tibetan Plateau

This paper presents the development of a new software tool IRA-WDS. This GIS-based software predicts the risks associated with contaminated water entering water distribution systems from surrounding foul water bodies such as sewers, drains and ditches. Intermittent water distribution systems are common in developing countries and these systems are prone to contamination when empty. During the non-supply hours contaminants from pollution sources such as sewers, open drains and surface water bodies enter into the water distribution pipes through leaks and cracks. Currently there are no tools available to help engineers identify the risks associated with contaminant intrusion into intermittent water distribution systems. Hence it is anticipated that IRA-WDS will find wide application in developing countries. The paper summarises the details of the mathematical models that form the basis of IRA-WDS. It also describes the software architecture, the main modules, and the integration with GIS using a tight coupling approach. A powerful GUI has been developed that enables data for the models to be retrieved from the spatial databases and the outputs to be converted into tables and thematic maps. This is achieved seamlessly through DLL calling functions within the GIS. This paper demonstrates the application of the software to a real case study in India. The outputs from IRA-WDS are risk maps showing the risk of contaminant intrusion into various parts of the water distribution system. The outputs also give an understanding of the main factors that contribute to the risk.

IRA-WDS: A GIS-based risk analysis tool for water distribution systems

This book has been written specifically for practitioners involved in the operation, maintenance and management of piped water distribution systems in urban areas of developing countries. These practitioners include engineers, planners, managers, and water professionals involved in the monitoring, control and rehabilitation of water distribution networks. This book is a manual for using the developed software, IRA-WDS (Improved Risk Assessment for Water Distribution Systems), a Geographical Information System (GIS) that aids in evaluating the risk of deterioration of the water distribution network of a water supply system. The manual is a structured document and explains a step-by-step procedure for using the IRA-WDS, with examples. The software IRA-WDS has been developed to evaluate risks to piped water distribution systems of urban areas in developing countries. This manual enables the use of this software. The software consists of three models, namely the Contaminant Ingress Model, Pipe Condition Assessment Model and Risk Assessment Model. The IRA-WDS is designed to use these models together or individually. This manual provides a step-by-step procedure for using these models and obtaining results. Water Safety Plans Book 3, also developed in this series, should be used along with the software and this manual. This will enable readers to understand and analyse their results. The WEDC Water Safety Plans series comprises: Book 1: Planning Water Safety Management for Urban Piped Water Supplies in Developing Countries; Book 2: Supporting Water Safety Management for Urban Piped Water Supplies in Developing Countries; Book 3: Risk Assessment of Contaminant Intrusion into Water Distribution Systems; Book 4: IRA-WDS Software and Manual for Risk Assessment of Contaminant Intrusion into Water Distribution Systems.

Water safety plans: Book 4. IRA-WDS software and manual for risk assessment of contaminant intrusion into water distribution systems.

This book has been written specifically for practitioners involved in the operation, maintenance and management of piped water distribution systems in urban areas of developing countries. These practitioners include engineers, planners, managers, and water professionals involved in the monitoring, control and rehabilitation of water distribution networks. The book explains in detail how to evaluate the risk of deterioration of the water distribution network of a water supply system. It begins with the conceptualization of risk evaluation and its three different components (hazard, vulnerability and risk). The book further elaborates on each of these three components, explains the methodologies used to estimate the components, and presents the background to the mathematical models. Finally, the book explains how these components are integrated to form a GIS-based decision support system for risk evaluation. The book is designed to help practitioners understand the concept of risk evaluation and supports the manual of the IRA-WDS software, a GIS-based decision support system for risk evaluation. The IRA-WDS software is developed for the evaluation of risk to piped water distribution systems in urban areas of developing countries. The user of this software needs to know about the consideration of different factors, data type and requirement, which may vary from one region to another. The user can understand the concept of evaluation from this book and decide upon the importance of the different factors involved and associated data collection. It should be noted that combining this book with Water Safety Plans Book 1 provides the decision-maker with a valuable tool to assess the overall risk of contaminant intrusion into a water supply system. It is also important to consider this book in relation to Water Safety Plans Book 2, as it is imperative that the institutions and authorities responsible for water management have the capacity to use and implement IRA-WDS, and also to recognize the importance of developing an integrated approach to water management. The WEDC Water Safety Plans series comprises: Book 1: Planning Water Safety Management for Urban Piped Water Supplies in Developing Countries; Book 2: Supporting Water Safety Management for Urban Piped Water Supplies in Developing Countries; Book 3: Risk Assessment of Contaminant Intrusion into Water Distribution Systems; Book 4: IRA-WDS Software and Manual for Risk Assessment of Contaminant Intrusion into Water Distribution Systems.

Water safety plans - Book 3: Risk assessment of contaminant intrusion into water distribution systems

The paper presents a GIS based spatial decision support system for modelling contaminant intrusion into water distribution system. Three models have been developed to simulate the process and risk of contamination. A seepage model predicts the contaminant zone of pollution sources and the change of concentration during migration through soil. A pipe condition assessment model ranks the condition of water pipe in terms of the potential of contaminant ingress. An ingress model combines the geometry algorithm with contaminant zone to obtain the potential pollution areas of water distribution pipe. The three models were integrated with ArcView GIS for supporting decision making for risk mitigation. Zone VIII of water supply system in Guntur, India was selected for the case study. The contaminant ingress potential and potential pollution area of water pipes were displayed as thematic maps in GIS. The areas resulting in high risk were identified from the GIS maps. The availability of resources for maintenance activities are limited in developing countries. Thus GIS based spatial decision support system helps to achieve maximum risk reduction.

Harshal Galgale

Papers

IRA-WDS: A GIS-based risk analysis tool for water distribution systems

Water safety plans: Book 4. IRA-WDS software and manual for risk assessment of contaminant intrusion into water distribution systems.

Water safety plans - Book 3: Risk assessment of contaminant intrusion into water distribution systems

A GIS based spatial decision support system for modelling contaminant intrusion into water distribution systems