Showing papers in "Journal of Water Resources Planning and Management in 2010"

State of the Art for Genetic Algorithms and Beyond in Water Resources Planning and Management

Abstract: During the last two decades, the water resources planning and management profession has seen a dramatic increase in the development and application of various types of evolutionary algorithms (EAs). This observation is especially true for application of genetic algorithms, arguably the most popular of the several types of EAs. Generally speaking, EAs repeatedly prove to be flexible and powerful tools in solving an array of complex water resources problems. This paper provides a comprehensive review of state-of-the-art methods and their applications in the field of water resources planning and management. A primary goal in this ASCE Task Committee effort is to identify in an organized fashion some of the seminal contributions of EAs in the areas of water distribution systems, urban drainage and sewer systems, water supply and wastewater treatment, hydrologic and fluvial modeling, groundwater systems, and parameter identification. The paper also identifies major challenges and opportunities for the future, ...

Simulating Residential Water Demand with a Stochastic End-Use Model

Abstract: A water demand end-use model was developed to predict water demand patterns with a small time scale (1 s) and small spatial scale (residence level). The end-use model is based on statistical inform...

Design criteria of urban drainage infrastructures under climate change.

Abstract: Actual projections provided by climate models suggest that the probability of occurrence of intense rainfall will increase in a future climate due to increasing concentrations of greenhouse gases. Considering that the design of urban drainage systems is based on statistical analysis of past events, an increase in the intensity and frequency of extreme rainfall events will most probably result in more frequent flooding. The design criteria must therefore be revised to take into consideration possible changes induced by climate change. A procedure is proposed to revise the design criteria of urban drainage infrastructures. This procedure integrates information about (1) climate projections for extreme rainfall over the region under consideration; (2) expected level of performance (or acceptable level of risk); and (3) expected lifetime of the infrastructure/system. The resulting design criterion ensures that the service level remains above the selected “acceptable” level over a predefined portion of the inf...

Optimization of Water Distribution Network Design Using Differential Evolution

Abstract: The paper describes the development of a DENET computer model that involves the application of an evolutionary optimization technique, differential evolution, linked to the hydraulic simulation solver, EPANET, for optimal design of water distribution networks. A model is formulated with the objective of minimizing cost and this formulation is applied to two benchmark water distribution system optimization problems—New York water supply system and Hanoi water distribution network. The study yielded promising results as compared with earlier studies in the literature and encouraged to reformulate the model for a new objective of maximizing network resilience. The results of the analysis demonstrate that DENET can be considered as a potential alternative tool for economical and reliable water distribution network planning and management.

Review of Sensor Placement Strategies for Contamination Warning Systems in Drinking Water Distribution Systems

Abstract: Contamination warning systems (CWSs) are a promising approach for the mitigation of contamination risks in drinking water distribution systems. A critical aspect of the design of a CWS is the strategic placement of online sensors that rapidly detect contaminants. This paper reviews the array of optimization-based sensor placement strategies that have been recently proposed. These strategies are critiqued and several key issues are identified that need to be addressed in future work.

Development and Verification of an Online Artificial Intelligence System for Detection of Bursts and Other Abnormal Flows

Abstract: Water lost through leakage from water distribution networks is often appreciable. As pressure increases on water resources, there is a growing emphasis for water service providers to minimize this loss. The objective of the work presented in this paper was to assess the online application and resulting benefits of an artificial intelligence system for detection of leaks/bursts at district meter area (DMA) level. An artificial neural network model, a mixture density network, was trained using a continually updated historic database that constructed a probability density model of the future flow profile. A fuzzy inference system was used for classification; it compared latest observed flow values with predicted flows over time windows such that in the event of abnormal flow conditions alerts are generated. From the probability density functions of predicted flows, the fuzzy inference system provides confidence intervals associated with each detection, these confidence values provide useful information for f...

Case Studies of Leak Detection and Location in Water Pipe Systems by Inverse Transient Analysis

Abstract: The current paper aims at the assessment of the effectiveness of a popular transient-based technique—inverse transient analysis (ITA)—for leak detection in water pipe systems using physical data. Data were collected from two pipe systems made of polyethylene: a laboratory facility at Imperial College London and a quasi-field system at Thames Water Utilities. A hydraulic transient solver especially developed for viscoelastic pipes (typically made of polyethylene) and an optimization algorithm for the simultaneous creep calibration and leak location have been developed for the application of this technique. The evaluation of the presence, location, and size of leaks was carried out using collected data. ITA allowed for the identification of the approximate location of leaks as long as the physical characteristics of the pipeline are well known, the transient is generated by a fast change of flow conditions, the leak has a “reasonable size,” and the transient solver is accurate enough to describe the transie...

Pressure-dependent leak detection model and its application to a district water system

Abstract: Cost-effective reduction of water loss is a compelling but challenging task for water utilities. This paper presents a model-based optimization method for leakage detection of water distribution systems. Leakage hotspots are assumed to exist at the model nodes identified. Leakage is represented as pressure-dependent demand simulated as emitter flows at selected model nodes. The leakage detection method is formulated to optimize the leakage node locations and their associated emitter coefficients such that the differences between the model predicted and the field observed values for pressure and flow are minimized. The optimization problem is solved by using a competent genetic algorithm. The leakage detection method is developed as an add-on feature of the optimization-based model calibration tool. This enables engineers to undertake leakage hotspot optimization as an independent task or combine the task with hydraulic model calibration, subject to suitably varied field data. Two case studies are discusse...

Seasonal Residential Water Demand Forecasting for Census Tracts

Abstract: The paucity of readily available demographic, economic, and water consumption data at household levels has limited the application of disaggregate water demand models. This research develops regres...

Energy audit of water networks.

Abstract: This paper presents the energy audit of a water network, which is obtained from the energy equation in integral form, and its time integration extended over a given period (day, month, or year). The analysis allows accounting for all the energy in the system, showing that the energy balance is maintained. This balance can be used to obtain performance indicators to assess the system from the energetic point of view. From these indicators, it is possible to identify the improvement actions that will make the system more efficient. This energy audit requires a previous water balance and the mathematical model of the network, both of which are necessary to know the energy flows through the system’s boundaries.

Accounting for Greenhouse Gas Emissions in Multiobjective Genetic Algorithm Optimization of Water Distribution Systems

Abstract: Considerable research has been carried out on the optimization of water distribution systems WDSs over the last three decades. In previous research, attention has mainly focused on the minimization of cost, due to the high expenditure associated with the construction and maintenance of such systems. However, the impacts of WDSs on the environment usually have not been considered adequately. The recent increasing awareness of sustainability and climate change, especially global warming, has led to research where greenhouse gas GHG emissions are considered. In the study described in this paper a multiobjective genetic algorithm for WDS optimization has been used as an explorative tool to investigate the trade-offs between the traditional economic objective of minimizing costs and an additional environmental objective of minimizing GHG emissions. The impacts of minimizing GHG emissions on the results of WDS optimization have been explored for a case study in this paper. The results indicate that the inclusion of GHG emission minimization as one of the objectives results in significant trade-offs between the economic and environmental objectives. Furthermore, a sensitivity analysis has been conducted by using different discount rates in a present value analysis for computing both ongoing costs and GHG emissions. The results obtained show that the Pareto-optimal front is very sensitive to the discount rates used. As a result, the selection of discount rates has a significant impact on final decision making.

Building Damage due to Riverine and Coastal Floods

Abstract: Floods in both riverine and coastal zones can cause significant damage to infrastructure, including possible structural failure of buildings. Methodologies commonly used to estimate flood damage to buildings are typically based on aftermath surveys and statistical analyses of insurance claims data. These methodologies rarely account for flooding hydrodynamics, and thus do not differentiate between the damage caused by floodwater contact and those caused by floodwater velocity. A new stochastic methodology has been developed to estimate the direct impact of flood actions on buildings and to determine the expected damage. Building vulnerability is modeled based on analytical representations of the failure mechanisms of individual building components. The flood actions generated during different flooding events are assessed and compared to the resistance of each building component. The assessed flood actions include: hydrostatic and hydrodynamic forces, waves, turbulent bores, debris impacts, and time-depend...

Economic Analysis of Large-Scale Upstream River Basin Development on the Blue Nile in Ethiopia Considering Transient Conditions, Climate Variability, and Climate Change

Abstract: The upper Blue Nile Basin in Ethiopia harbors considerable untapped potential for irrigation and large-scale hydropower development and expansion. Numerous water resources system models have been developed to evaluate these resources, yet often fail to adequately address critical aspects, including the transient e.g., filling stages of reservoirs, relevant streamflow retention policies and downstream consequences, construction staggering, and the implications of stochastic modeling of variable climate and climate change. This omission has clear economic impacts on benefits and costs and could be pivotal in national policy and decision making. The Investment Model for Planning Ethiopian Nile Development dynamic water resources system model is outlined and applied to address these aspects. For the hydropower and irrigation development projects specified, model results disregarding transient and construction stagger aspects demonstrate overestimations of $6 billion in benefits and 170% in downstream flows compared to model results account- ing for these aspects. Benefit-cost ratios for models accounting for transient conditions and climate variability are found to range from 1.2-1.8 under historical climate regimes for the streamflow retention policies evaluated. Climate change scenarios, represented either by changes in the frequency of El Nino and La Nina events or by the Special Report on Emissions Scenarios projections, indicate potential for small benefit-cost increases, but also reflect the potential for noteworthy decreases, relative to the historical climate conditions. In particular, stochastic modeling of scenarios representing a doubling of the historical frequency of El Nino events indicates benefit-cost ratios as low as 1.0, even under perfect foresight optimization modeling, due to a lack of timely water. However, even at this ratio, Ethiopia, at current growth rates, may still be unable to absorb all the potential energy developed, reinforcing the need for significant economic planning and the necessity of securing energy trade contracts prior to extensive expansion.

Optimal operation of complex water distribution systems using metamodels.

Abstract: Optimization of large and hydraulically complex water distribution systems (WDSs) is computationally expensive as simulation models are required to evaluate the performance of solutions to the problem at hand. Metamodels can act as a surrogate or substitute for these simulation models and provide significant speed-ups in the optimization process. The application of metamodels in the field of WDS optimization has been limited to date, and little guidance has been given in terms of constructing metamodels for hydraulically complex systems. While it is relatively straightforward to obtain satisfactory metamodel approximations to simulation models of simple WDSs, this is not necessarily the case for more complex networks. In order to reduce the complexity of the relationship that is to be approximated by the metamodels, a number of factors have to be considered, including the complexity of the hydraulic simulation model, the complexity of the decision space, and the locations at which outputs are required fro...

Single-Objective versus Multiobjective Optimization of Water Distribution Systems Accounting for Greenhouse Gas Emissions by Carbon Pricing

Abstract: Previous research has demonstrated that there are significant trade-offs between the competing objectives of minimizing costs and greenhouse gas (GHG) emissions for water distribution system (WDS) optimization. However, upon introduction of an emission trading scheme, GHG emissions are likely to be priced at a particular level. Thus, a monetary value can be assigned to GHG emissions, enabling a single-objective optimization approach to be used. This raises the question of whether the introduction of carbon pricing under an emission trading scheme will make the use of a multiobjective optimization approach obsolete or whether such an approach can provide additional insights that are useful in a decision-making context. In this paper, the above questions are explored via two case studies. The optimization results obtained for the two case studies using both single-objective and multiobjective approaches are analyzed. The analyses show that the single-objective approach results in a loss of trade-off informa...

Risk-Based Sensor Placement for Contaminant Detection in Water Distribution Systems

Abstract: A method for optimizing sensor locations to effectively and efficiently detect contamination in a water distribution network is presented here. The problem is formulated and solved as a twin-objective optimization problem with the objectives being the minimization of the number of sensors and minimization of the risk of contamination. Unlike past approaches, the risk of contamination is explicitly evaluated as the product of the likelihood that a set of sensors fails to detect contaminant intrusion and the consequence of that failure (expressed as volume of polluted water consumed prior to detection). A novel importance-based sampling method is developed and used to effectively determine the relative importance of contamination events, thus reducing the overall computation time. The above problem is solved by using the nondominated sorting genetic algorithm II. The methodology is tested on a case study involving the water distribution system of Almelo (The Netherlands) and the potential intrusion of E. co...

Optimal Design of Sensor Placement in Water Distribution Networks

Abstract: In this study we provide a methodology for the optimal design of water sensor placement in water distribution networks. The optimization algorithm used is based on a simulation-optimization and a s...

Building Water Resilience in the Face of Global Change: From a Blue-Only to a Green-Blue Water Approach to Land-Water Management

Abstract: Building Water Resilience in the Face of Global Change : From a Blue-Only to a Green-Blue Water Approach to Land-Water Management.

Multiobjective Optimization of Operational Responses for Contaminant Flushing in Water Distribution Networks

Abstract: Contamination emergency in water distribution systems is a complex situation where optimal operation becomes important for public health. In case of emergency corrective operational actions for flushing the pollutant out of the network are needed, which have to be fast and accurate. Under such a stressful situation, trial-and-error simulation experiments with the hydrodynamic and water quality models cannot be applied since significant number of model evaluations may be required to identify the optimal solution. This paper presents a methodology for finding sets of operational interventions in a supply network for flushing a contaminant by minimizing the impact on the population. The situation is treated as both single- and multiobjective optimization problem, which is solved by using evolutionary optimization approaches, in combination with the EPANET solver engine. The methodology is tested on a simple imaginary network configuration, as well as on a real case study for the city of Villavicencio in Colombia. The results prove the usefulness of the approach for advising the operators and decision makers.

Real-Time Identification of Possible Contamination Sources Using Network Backtracking Methods

Abstract: In case of contamination intrusion in water distribution systems, water quality sensor data can be used to determine the location and time of the contamination source. One approach to contamination source identification is finding the source location that minimizes the difference between modeled and measured water quality. However, this is an inherently ill-posed mathematical problem, due to the shortage of measurements compared to source parameters, and regularization methods are required to force identification of a unique solution. An alternative practical method is developed in this paper to identify all possible locations and times that explain contamination incidents detected by the water quality sensors. Since sensors cannot detect the quantitative concentration of a contaminant, this method only requires a binary sensor status over time. A particle backtracking algorithm is used to identify the water flow paths and travel times leading to each sensor measurement. Those locations and times that are...

Urban Storm-Water Quality Management: Centralized versus Source Control

Abstract: The continuous growth of urban areas and the increasing public awareness of the environmental impacts of storm water have raised interest on the quality of the receiving water bodies. In the past two decades, many efforts have been directed at improving urban drainage systems by introducing mitigation measures to limit the negative environmental impacts of storm water. These mitigation measures are generally called best management practices (BMPs), sustainable urban drainage systems, or low impact developments, and they include practices such as infiltration and storage tanks that reduce the peak flow and retain some of the polluting materials. Choosing the best mitigation measure is still a controversial topic. To gain insight on the best technique, this study compares different distributed and centralized urban storm-water management techniques, including infiltration and storage facilities. The main objective of this study is to use modeling to assess the effects of the different urban drainage techniq...

Impacts and Uncertainty of Climate Change on Water Resource Management of the Peribonka River System "Canada…

Abstract: The impacts of climate change on medium-term reservoir operations for the Peribonka water resource system Quebec, Canada were evaluated with annual and seasonal hydropower production indicators and flood control criteria. According to simulations under the current operating rules in a climate change context, the tendency is for a reduction in mean annual hydropower production and an increase in spills, despite an increase in the annual average inflow to the reservoirs. The main results indicate that annual mean hydropower would change by 12 to +2%, and spills by 49 to +152%. A broad range of climate projections—a combination of five general circulation models with two greenhouse gas scenarios each—were used in order to evaluate the uncertainty of these future potential climates on floods and hydroelectric production. Climate projections were downscaled with the change factor method also called the Delta method at a horizon centered in 2050. To represent natural variability, a stochastic weather generator was used to produce 30 synthetic climate series of 30 years each, representative of each climate change projection as well as of the climate of the control period. The hydrological impacts of climate change were evaluated with a lumped hydrological model and the hydrological regimes were analyzed according to spring flood characteristics and the average inflows. In general, the projections indicate an increase in annual inflow, earlier peaks and greater volumes during the spring flood. The analyses show that a power plant managed with a reservoir is sensitive to the operating rules and that these rules should be re-examined in order to take account of new seasonal hydrological contexts.

Scheduling Renewal of Water Pipes While Considering Adjacency of Infrastructure Works and Economies of Scale

Abstract: Much research effort has been dedicated to the development of optimal strategies for rehabilitation and/or replacement of water mains. Some of the methods are intended for high-level planning of groups or cohorts of pipes, while others address low-level scheduling of individual water mains. This paper focuses on the latter aspect. An approach is proposed for the efficient scheduling of individual water mains for replacement in a short to medium predefined planning period and subject to various budgetary constraints. This approach also accounts for economies of scale considerations as well as harmonization with other known infrastructure works. A multiobjective genetic algorithm scheme is used as a tool to search a vast combinatorial solution space, comprising various combinations of pipe replacement schedules.

RTC of Valves for Leakage Reduction in Water Supply Networks

Abstract: This paper reports the results of a numerical investigation aimed at assessing the effectiveness of the real-time control (RTC) of valves in reducing leakage in water supply networks. The investigation was carried out considering the head-driven simulation of a network under successive steady conditions. A literature bench-test case-study was used for the simulations enabling the comparison with other methodologies proposed by previous writers and based on the use of optimization algorithms. The performance of RTC was evaluated in terms of pressure and leakage reduction with respect to uncontrolled conditions in the network. Further elaborations showed the better flexibility of RTC, with respect to optimization algorithms, in adjusting valve regulation under variable daily water demand conditions.

Real-Time Optimal Valve Operation and Booster Disinfection for Water Quality in Water Distribution Systems

Abstract: Historically, a water distribution system’s (WDS) hydraulic performance has been the primary operational concern. Over the past two decades, however, more attention has been paid to water quality behavior in WDS and today, water quality level is an equally important issue for many water utilities. In most cases, maintaining disinfectant levels is usually of interest to avoid the bacteria regrowth and to protect against the potential cross-contamination events. However, disinfectants, such as chlorine, decay over time and produce potentially harmful disinfectant by-products when they react with organic material in the water. Therefore, maintaining a minimum chlorine residual requirement throughout the WDS is a complex but important task. When online booster disinfection is combined with source disinfection, it has been shown that the total chlorine dosage can be reduced while maintaining minimum chlorine residuals across the system. Here, optimal valve operation has been combined with booster disinfection ...

Design Robustness of Local Water-Recycling Schemes

Abstract: The implementation of local water recycling and reuse practices is considered as a possible approach to managing issues of water scarcity. The sustainable design and implementation of a water recycle/reuse scheme has to achieve an optimum compromise between costs (including energy) and benefits (potable water demand reduction). Another factor that should be taken into account is the influence of potential changes in climatic conditions to the scheme’s efficiency. These issues were assessed in this study using the urban water optioneering tool. Two water-recycling schemes, a rainwater harvesting and a combination of rainwater harvesting and local greywater recycling, were assessed. The trade-off between potable water demand reduction, capital/operational cost, and energy consumption of the two schemes was derived under three basic climatic conditions (oceanic, Mediterranean, and desert) using evolutionary optimization. Furthermore, the impact of changing climatic conditions on the suggested schemes was ana...

Novel Multiobjective Shuffled Frog Leaping Algorithm with Application to Reservoir Flood Control Operation

Abstract: Reservoir flood control operation (RFCO) is a large scale multiobjective problem with complex constraints that require powerful algorithms to solve it. As a new metaheuristic evolutionary algorithm, shuffled frog leaping algorithm (SFLA) has the potential ability to solve multiobjective optimization problems because of its group evolution characteristic. In this paper, we present a novel multiobjective shuffled frog leaping algorithm (MOSFLA), which incorporates an archiving strategy based on self-adaptive niche method to maintain the nondominated solutions, and improves the memetic evolution process of SFLA to adapt to the multiobjective optimization problem. The numerical experiments of five Zitzler-Deb-Thiele functions indicate that MOSFLA yields better-spread solutions and converges closer to the true Pareto frontier than non-denominated sorting genetic algorithm (NGSA)-II and SPEA2. Furthermore, MOSFLA is applied to solve RFCO of the Three Gorges Project, and the results demonstrate that this algorit...

Modeling Conjunctive Use Operations and Farm Decisions with Two-Stage Stochastic Quadratic Programming

Abstract: This paper applies two-stage stochastic quadratic programming to optimize conjunctive use operations of groundwater pump- ing and artificial recharge with farmer's expected revenue and cropping decisions. The two-stage programming approach allows modeling of water and permanent crop production decisions, with recourse for uncertain conditions of hydrology, annual crops, and irrigation technology decisions. Results indicate potential gains in expected net benefits and reduction in income variability from conjunctive use, with increase in high value permanent crops along with more efficient irrigation technology.

Robust Design of Water Distribution Networks for a Proactive Risk Management

Abstract: In the last three decades the optimal design of water distribution systems problem has been studied by a great many researchers, and this has resulted in the development of a large number of models and the application of optimization techniques. The design of these infrastructures is based on future predefined and perfectly known working conditions for the water distribution networks, a premise that may direct the optimization process to solutions which, although optimal for the imposed scenario, may perform badly if reality turns out to be significantly different. In fact the working conditions can be disrupted by accidents such as broken pipes or reservoirs, technical failures, change in demand, etc. In the context of a proactive attitude toward risk, it is important to consider these aspects at the design phase. This paper presents a robust optimization-based approach for designing a water distribution network aimed at obtaining solutions that can cope with the uncertainty of the network’s working cond...