Abstracts:Security issues have become increasingly important within drinking water distribution systems, leading to the development of event detection algorithms (EDAs) to provide timely detection of intrusion events. The current study develops a systemwide event detection algorithm that integrates the alarm information from localized model-based EDAs at individual monitoring stations with the probabilistic contamination source identification algorithm to estimate the probability that a node-time pair may have been contaminated. An alarm threshold can be set on the resulting contamination probabilities, which results in a systemwide EDA that takes advantage of integrating the distributed detection at all sensors rather than relying on single sensors. The systemwide EDA was evaluated with two injection scenarios simulated at two different injection locations to assess performance when all sensors observed the event versus when only one sensor observed the event. The results showed that for both injection locations and both injection scenarios, the integrated systemwide EDA outperformed the use of only the localized EDA for a series of detection thresholds based upon a range of false positive rates. These results support the assumption that including information from multiple sensors would improve event detection performance.

Abstracts:The construction of water transfer projects can have a considerable impact on the operation of the receiving reservoir. This study investigates the change of the objective trade-offs in multiobjective reservoir operation problems due to the introduction of water transfer using a case study of the east-to-west water transfer project in northeastern China. Two optimization cases are constructed to analyze the trade-off changes: a base case with no water transfer that considers four objectives, i.e., minimizing industry water shortage, minimizing agriculture water shortage, minimizing water spillage, and maximizing ecological satisfaction; and a future postconstruction case that considers an additional objective to minimize the amount of water transferred. Results obtained from the case study show increasing water transfer substantially reduces the intensity of the competition between industrial and agricultural water shortages, and the objective trade-offs among water spillage, ecological satisfaction, and agricultural shortage index are substantially changed because of water transfer. In addition, the amount of water transferred with high efficiency regarding each objective is identified, and three solutions of different orders of magnitude in diverted water have been recommended for informed decision making considering efficiency and benefit. This study implies that many-objective visual analytics can be used to determine the optimal amount of water transferred in terms of water efficiency revealed in different objective trade-off spaces.

Abstracts:An adaptive hybrid genetic algorithm (GA) and cellular automata (CA) method is proposed for solving implicit stochastic optimization of reservoir operation problems. The method is based on a decomposition approach in which the reliability constraints are handled with GA, whereas the resulting deterministic problem is solved with a CA model. Two versions, binary and integer GA, were employed for handling the reliability constraints of the problem. In the first one, GA was used to determine the success/failure pattern of the operation, whereas in the latter, only failure periods were determined with GA. The proposed method was used for monthly water supply and hydropower operation of an existing reservoir and the results are presented and compared with those of a GA model. To demonstrate the efficiency and scale independency of the model, short-term, medium-term, and long-term operations are considered assuming different target reliabilities. Comparison of the results with those of a GA model shows the superiority of the proposed method.

Abstracts:Low and constant pressure can be maintained throughout a water distribution system by setting the pressure at remote consumer locations and using the pressure to control the speed of a variable speed pump (VSP). The prospect of incorporating hydraulics theory into a controller is investigated, with the goal of improving on generic controllers. Five new controllers are proposed here, four of which depend on hydraulics theory. These controllers, which set the speed of the VSP, are investigated numerically. A parameter-dependent controller that does not require the flow in the pump to be known is developed and shown to significantly improve on the performance of conventional (parameter-dependent) proportional control (PC). Next, a parameter-free controller that requires the flow in the pump to be known is proposed and shown to outperform PC, even though PC has a tunable parameter, and perform comparably to the best new parameter-dependent controllers. The parameter-dependent controllers (when optimally tuned) perform best overall. The efficacy of many of the new controllers shows that hydraulics theory can lead to improved controllers.

Abstracts:Reliability, resilience, and vulnerability are the most commonly used performance criteria for water supply planning and management. However, there is lack of understanding of the relationships among these criteria. This paper aims to reveal the relationships among them by using emerging many-objective visual analytics. To measure different aspects of water supply systems in terms of reliability, resilience, and vulnerability, a suite of five metrics are considered: water supply reliability, mean and maximum deficits of water supply, and mean and maximum durations of water shortage. Results obtained in this study reveal that both conflicting and synergetic relationships exist between reliability and resilience (mean deficit of water supply), and between vulnerability (mean duration of water shortage) and resilience (mean deficit of water supply) in different regions of the objective space. A more complete picture of the relationships among reliability, resilience, and vulnerability than reported in the prior literature is provided in this paper thanks to the use of many-objective analysis. This study provides an in-depth understanding of the relationships and can help decision makers make an informed decision in the management of water resources systems.

Abstracts:The paper describes the development of a computer model GANET that involves the application of an area of evolutionary computing, better known as genetic algorithms, to the problem of least-cost design of water distribution networks. Genetic algorithms represent an efficient search method for nonlinear optimization problems; this method is gaining acceptance among water resources managers/planners. These algorithms share the favorable attributes of Monte Carlo techniques over local optimization methods in that they do not require linearizing assumptions nor the calculation of partial derivatives, and they avoid numerical instabilities associated with matrix inversion. In addition, their sampling is global, rather than local, thus reducing the tendency to become entrapped in local minima and avoiding dependency on a starting point. Genetic algorithms are introduced in their original form followed by different improvements that were found to be necessary for their effective implementation in the optimization of water distribution networks. An example taken from the literature illustrates the approach used for the formulation of the problem. To illustrate the capability of GANET to efficiently identify good designs, three previously published problems have been solved. This led to the discovery of inconsistencies in predictions of network performance caused by different interpretations of the widely adopted Hazen-Williams pipe flow equation in the past studies. As well as being very efficient for network optimization, GANET is also easy to use, having almost the same input requirements as hydraulic simulation models. The only additional data requirements are a few genetic algorithm parameters that take values recommended in the literature. Two network examples, one of a new network design and one of parallel network expansion, illustrate the potential of GANET as a tool for water distribution network planning and management.

Abstracts:Monitoring water quality in drinking water distribution systems is the basis for proactive approaches to prevent or manage emerging water quality issues, and such a monitoring requires a strategic selection of relevant and representative monitoring sites. GISMOWA is a new GIS and risk-based analysis tool to identify and prioritize pipe segments for water quality monitoring and to comply with existing monitoring and sampling guidelines. The tool was designed to integrate multiple parameters categorized as (1) hydraulic and structural weaknesses in the system, e.g., residence time; (2) external threats, e.g., contaminated sites; and (3) sensitive consumers, e.g., hospitals, in a GIS environment. The tool used a multicriteria decision analysis to evaluate multiple monitoring site parameters and map zones particularly suitable for water quality monitoring. GISMOWA was applied to Danish water distribution systems as a transparent and simple-to-use tool facilitating a complete overview of the distribution system, including sensitive consumers and consumers in general, thus fulfilling a precondition for a HACCP-based monitoring strategy of drinking water.

Abstracts:Isolation valves are crucial components of water distribution systems for separating pipe segments from the network for repair or maintenance purpose. This paper looks at the impacts of isolation valve failure on three indictors, including number of valves needed to isolate a distribution system segment, size of distribution system segments, and shortfall in meeting demands during failure. A network with various isolation valve configurations in terms of valve density is used as a case study. The results obtained from the case study show that the failure of an isolation valve has substantially varying impacts on system performance during a shutdown. The valve density in the network determines the impacts of inoperable valves on a shutdown. Generally speaking, a higher density of isolation valves leads to the less impact of valve failure. Finally, several conclusions drawn from the critical valve analysis in this study can be applied to guide isolation valve maintenance and management.

Abstracts:This paper proposes a fuzzy multiobjective programming model for meeting competing objectives in the optimal design of water distribution systems (WDSs). Fuzzy membership functions for minimizing the pipe network cost and maximizing a number of reliability surrogates are defined, and the model maximizes the degree of satisfaction of these membership functions. Reliability surrogates investigated include: (1) the sum over all nodes of the relative surplus of energy at each node; (2) the minimum surplus head at a critical node; (3) the sum over all nodes of the relative surplus of energy at each node modified by the degree of uniformity of its associated loop; and (4) the minimum uniformity of the associated loops over all nodes. The model is applied to various combinations of objective functions, to identify the design pipe diameters of the water-main network of Farhadgerd, Iran. Optimal solutions of the various model variations, based on inclusion of one or more reliability surrogate(s), show that for this WDS the third surrogate (3) may be a reasonable substitute for the first surrogate (1), and that while the inclusion of the last surrogate (4) may be beneficial, the inclusion of the second surrogate (2) may not. Based on postoptimization cut-set analyses, the model that minimizes cost and maximizes surrogates (3) and (4) exhibits the highest level of mechanical reliability, while the model that minimizes cost and maximizes the second surrogate (2) exhibits the lowest level of mechanical reliability.