| publications-4141 |
article |
2010 |
Tabucchi, Taronne H. P. and Tabucchi, Taronne H. P. and Davidson, Rachel A. and Davidson, Rachel A. and Brink, Susan and Brink, Susan A. and Brink, Susan |
Simulation of post-earthquake water supply system restoration |
Civil Engineering and Environmental Systems |
10.1080/10286600902862615 |
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This paper describes a discrete event simulation model of post-earthquake restoration for the Los Angeles Department of Water and Power water supply system. It mimics the real-life process in detail, simulating the movement of different types of crews as they inspect, reroute around, isolate, and repair system damage. For any given earthquake, the model provides restoration curves with uncertainty bounds, maps showing the spatial distribution of outages over time, and crew and repair material usage information. Results for the 1994 Northridge earthquake suggest the model is capable of accurately estimating the time and spatial sequence of the restoration. It can be useful for loss estimation and resilience assessment, evaluating the effectiveness of hypothetical restoration strategies, and improving understanding of the restoration process and its key determinants. This is the first application of discrete event simulation to post-disaster water supply restoration, and one of the first for any infrastruct... |
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| publications-4142 |
article |
2008 |
Davis, Michael J. and Janke, Robert |
Importance of Exposure Model in Estimating Impacts When a Water Distribution System is Contaminated |
Journal of Water Resources Planning and Management |
10.1061/(asce)0733-9496(2008)134:5(449) |
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The quantity of a contaminant ingested by individuals using tap water drawn from a water distribution system during a contamination event depends on the concentration of the contaminant in the water and the volume of water ingested. If the concentration varies with time, the actual time of exposure affects the quantity ingested. The influence of the timing of exposure and of individual variability in the volume of water ingested on estimated impacts for a contamination event has received limited attention. We examine the significance of ingestion timing and variability in the volume of water ingested by using a number of models for ingestion timing and volume. Contaminant concentrations were obtained from simulations of an actual distribution system for cases involving contaminant injections lasting from 1 to 24 h. We find that assumptions about exposure can significantly influence estimated impacts, especially when injection durations are short and impact thresholds are high. The influence of ingestion timing and volume should be considered when assessing impacts for contamination events. |
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| publications-4143 |
article |
2012 |
Alvisi, Stefano and Alvisi, Stefano and Franchini, Marco and Franchini, Marco and Gavanelli, Marco and Gavanelli, Marco and Nonato, Maddalena and Nonato, Maddalena |
Near-optimal scheduling of device activation in water distribution systems to reduce the impact of a contamination event |
Journal of Hydroinformatics |
10.2166/hydro.2011.147 |
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This paper proposes an innovative procedure for identifying, in the event of accidental or intentional contamination of a water distribution system, the optimal scheduling of activation of a pre-selected set of flow control devices which will serve to minimise the volume of contaminated water consumed by users after the detection of the contaminant in the system. The constraints are represented by the number of available response teams and the maximum speed at which these teams can travel along the roadway. The optimal scheduling of device activation is sought by means of an optimisation process based on a genetic algorithm (GA) which interacts with a mixed integer linear programming (MILP) solver in order to ensure the feasibility of the scheduling identified. The optimisation procedure is coupled to a hydraulic and quality simulator, which enables a calculation of the volumes of contaminated water consumed by users, and a dynamic cache memory, which, by storing information on the system9s behaviour as the optimisation process progresses, serves to limit the computational times. The application of the procedure to a highly complex real water distribution system shows that the optimisation process is robust and efficacious and produces a smaller volume of contaminated water consumed by the users than when the activation of all the devices was completed in the shortest amount of time. |
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| publications-4144 |
article |
2013 |
Islam, Nilufar and Islam, Nilufar and Sadiq, Rehan and Sadiq, Rehan and Rodriguez, Manuel J. and Rodriguez, Manuel J. |
Optimizing booster chlorination in water distribution networks: a water quality index approach |
Environmental Monitoring and Assessment |
10.1007/s10661-013-3153-z |
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The optimization of chlorine dosage and the number of booster locations is an important aspect of water quality management in distribution networks. Booster chlorination helps to maintain uniformity and adequacy of free residual chlorine concentration, essential for safeguarding against microbiological contamination. Higher chlorine dosages increase free residual chlorine concentration but generate harmful by-products, in addition to taste and odor complaints. It is possible to address these microbial, chemical, and aesthetic water quality issues through free residual chlorine concentration. Estimating a water quality index (WQI) based on regulatory chlorine thresholds for microbial, chemical, and aesthetics criteria can help engineers make intelligent decisions. An innovative scheme for maintaining adequate residual chlorine with optimal chlorine dosages and numbers of booster locations was established based on a proposed WQI. The City of Kelowna (BC, Canada) water distribution network served to demonstrate the application of the proposed scheme. Temporal free residual chlorine concentration predicted with EPANET software was used to estimate the WQI, later coupled with an optimization scheme. Preliminary temporal and spatial analyses identified critical zones (relatively poor water quality) in the distribution network. The model may also prove useful for small or rural communities where free residual chlorine is considered as the only water quality criterion. |
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| publications-4145 |
article |
2005 |
Kroll, Dan and Kroll, Dan and Throckmorton, Jeff and Throckmorton, Jeff |
The role of technology in enhancing water security: protecting a valuable asset (Keynote Paper) |
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10.1117/12.606940 |
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Drinking water is one of the nation's key infrastructure assets that have been deemed vulnerable to deliberate terrorist attacks. While the threat to reservoir systems and water sources is deemed to be minimal, the vulnerability of the drinking water distribution systems to accidental or deliberate contamination due to a backflow event is becoming a well-recognized possibility. The myriad possible points of incursion into a distribution system and the ease of mounting a backflow event, combined with the fact that little or no quality monitoring occurs after the water has left the treatment plant, makes the danger of such an attack acute. This was clearly stated in a General Accounting Office (GAO) report to Congress that listed the vulnerability of the distribution system to attack as the largest security risk to water supplies. Prior to this there has not been a system capable of detecting such an event and alerting the system's managers so that effects of an attack or accident can be contained. The general scientific consensus is that no practical, available, or cost-effective real-time technology exists to detect and mitigate intentional attacks or accidental incursions in drinking water distribution systems. The rapid detection and identification of breaches of security in the water distribution system is crucial in initiating appropriate corrective action. The ability of a technology system to detect incursion on a real time basis and give indications as to the cause could dramatically reduce the impact of any such scenario. As the vulnerability of the distribution system becomes more widely recognized, the development of a system such as the one described will be an invaluable tool in maintaining the integrity of the nations drinking water supply.Β© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
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| publications-4146 |
article |
2013 |
Wang, Hui and Wang, Hui and Harrison, Kenneth W. and Harrison, Kenneth W. |
Bayesian approach to contaminant source characterization in water distribution systems: adaptive sampling framework |
Stochastic Environmental Research and Risk Assessment |
10.1007/s00477-013-0727-9 |
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Bayesian analysis can yield a probabilistic contaminant source characterization conditioned on available sensor data and accounting for system stochastic processes. This paper is based on a previously proposed Markov chain Monte Carlo (MCMC) approach tailored for water distribution systems and incorporating stochastic water demands. The observations can include those from fixed sensors and, the focus of this paper, mobile sensors. Decision makers, such as utility managers, need not wait until new observations are available from an existing sparse network of fixed sensors. This paper addresses a key research question: where is the best location in the network to gather additional measurements so as to maximize the reduction in the source uncertainty? Although this has been done in groundwater management, it has not been well addressed in water distribution networks. In this study, an adaptive framework is proposed to guide the strategic placement of mobile sensors to complement the fixed sensor network. MCMC is the core component of the proposed adaptive framework, while several other pieces are indispensable: Bayesian preposterior analysis, value of information criterion and the search strategy for identifying an optimal location. Such a framework is demonstrated with an illustrative example, where four candidate sampling locations in the small water distribution network are investigated. Use of different value-of-information criteria reveals that while each may lead to different outcomes, they share some common characteristics. The results demonstrate the potential of Bayesian analysis and the MCMC method for contaminant event management. |
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| publications-4147 |
article |
2015 |
Hua, Pei and Vasyukova, Ekaterina and Uhl, Wolfgang |
A variable reaction rate model for chlorine decay in drinking water due to the reaction with dissolved organic matter. |
Water Research |
10.1016/j.watres.2015.01.037 |
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| publications-4148 |
article |
2005 |
Barthel, Roland and Barthel, Roland and Rojanschi, V. and Rojanschi, V. and Wolf, Jens and Wolf, Jens and Braun, J. and Braun, JΓΌrgen and Braun, Juergen |
Large-scale water resources management within the framework of GLOWA-Danube. Part A: The groundwater model |
Physics and Chemistry of The Earth |
10.1016/j.pce.2005.06.003 |
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| publications-4149 |
article |
2014 |
Oliker, Nurit and Oliker, Nurit and Ostfeld, Avi and Ostfeld, Avi |
A coupled classification – Evolutionary optimization model for contamination event detection in water distribution systems |
Water Research |
10.1016/j.watres.2013.10.060 |
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| publications-4150 |
article |
2012 |
Wise, Sarah and Wise, Sarah and Crooks, Andrew and Crooks, Andrew |
Agent-based modeling for community resource management: Acequia-based agriculture |
Computers, Environment and Urban Systems |
10.1016/j.compenvurbsys.2012.08.004 |
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