Showing papers in "Journal of Water Resources Planning and Management in 2013"

Automated Creation of District Metered Area Boundaries in Water Distribution Systems

Abstract: Accounting for water in a distribution system can be improved by dividing systems into smaller, metered zones. This paper proposes an approach that could create boundaries for district metered areas (DMA) automatically on the basis of the community structure of water distribution systems. Community structure—the gathering of vertices into communities such that there is a higher density of edges within communities than between them—is a common property of many complex systems. For verification, the method was tested on a real-world distribution system, and the result was compared with a manually designed DMA layout. Although further improvements are necessary, because the achieved community structure is in excellent agreement with the zoning plan in reality, this approach is a new addition to the number of automated methods aimed at complementing and eventually substituting the empirical trial-and-error approach.

Optimal Design of Water Distribution Systems Using Many-Objective Visual Analytics

Abstract: This paper reports the use of many-objective optimization for water distribution system (WDS) design or rehabilitation problems. The term many-objective optimization refers to optimization with four or more objectives. The increase in the number of objectives brings new challenges for both optimization and visualization. This study uses a multiobjective evolutionary algorithm termed the epsilon Nondominated Sorted Genetic Algorithm II (e-NSGAII) and interactive visual analytics to reveal and explore the tradeoffs for the Anytown network problem. The many-objective formulation focuses on a suite of six objectives, as follows: (1) capital cost, (2) operating cost, (3) hydraulic failure, (4) leakage, (5) water age, and (6) fire-fighting capacity. These six objectives are optimized based on decisions related to pipe sizing, tank siting, tank sizing, and pump scheduling under five different loading conditions. Solving the many-objective formulation reveals complex tradeoffs that would not be revealed i...

Methods and Tools for Managing Losses in Water Distribution Systems

Abstract: The water industry worldwide is facing challenges of water and revenue losses. To reduce these losses and improve efficiency of water distribution systems, tools and methods have been developed over the years. This paper reviews the current tools and methodologies applied to assess, monitor, and control losses in water distribution systems. The aim is to identify the tools and methods that have been applied, knowledge gaps, and future research needs. The review findings indicate that a number of water loss management tools and methods have been developed and applied. They vary from simple managerial tools such as performance indicators to highly sophisticated optimization methods such as evolutionary algorithms. However, their application to real-world water distribution systems has been found to be generally limited. Future research opportunities exist through close collaboration of research institutions and water service providers to close the gap between theory and applications. Although not ex...

Assessment of Flow Changes from Hydropower Development and Operations in Sekong, Sesan, and Srepok Rivers of the Mekong Basin

Abstract: The Mekong River supports unique biodiversity and provides food security for over 60 million people in the Indo-Burma region, yet potential changes to natural flow patterns from hydropower development are a major risk to the well-being of this system. Of particular concern is the ongoing and future development of 42 dams in the transboundary Srepok, Sesan and Sekong (3S) basin, which contributes up to 20% of the Mekong’s annual flows and provides critical ecosystem services to the downstream Tonle Sap Lake and the Mekong Delta. To assess the magnitude of potential changes, daily flows were simulated over 20 years using the HEC ResSim and SWAT models for a range of dam operations and development scenarios. A 63% increase in dry season flows and a 22% decrease in wet season flows at the outlet of the 3S basin could result from the potential development of new dams in the main 3S rivers under an operation scheme to maximize electricity production. Water-level changes in the Mekong River from this sce...

Fast Hybrid Optimization Method for Effective Pump Scheduling

Abstract: The cost of electricity used for pumping in water-distribution systems typically represents the largest part of the total operational costs. Therefore, optimization of pump operations is a ...

Bilevel Optimization of Regional Water Resources Allocation Problem under Fuzzy Random Environment

Abstract: The allocation of water resources has long been recognized as a critical optimization problem. In this study, a bilevel programming model with fuzzy random variables is developed for tackling a regional water resources allocation problem on the basis of water rights distribution in a river basin. The bilevel programming model takes the optimal total benefit of the society and the optimal economic benefit of each subarea as the upper and lower targets, respectively. In contrast to previous studies, the balance of the satisfactory degree between the upper and lower decision makers is considered in the bilevel optimization for ensuring the equity of the water resource allocation. To deal with inherent uncertainties, the fuzzy random variables are first transformed into trapezoidal fuzzy numbers, and by taking advantage of the expected value operation, the trapezoidal fuzzy numbers are subsequently defuzzified. For solving the complex and nonlinear bilevel programming model, an interactive fuzzy progr...

Simulation-Optimization Approach to Design Low Impact Development for Managing Peak Flow Alterations in Urbanizing Watersheds

Abstract: The process of urbanization transforms natural landscape into impervious land cover, affecting the ecosystem health of receiving water bodies and downstream communities by changing the timing and volumes of the natural flow regime. Best management practices (BMP) and low impact development (LID) are a set of mitigating measures that can be considered for watershed management to mitigate the hydrologic consequences of urbanization. This research develops a methodology to select sites for placing LID technologies, namely rainwater harvesting and permeable pavements, to reduce hydrologic impacts, measured as alterations to the peak flow while meeting a prespecified budget. A simulation-optimization methodology couples a genetic algorithm with a hydrologic model, a hydraulic model, and curve number-based models of LID technologies. The trade-off between costs and peak flow alteration is explored by optimizing LID placement under varying budget constraints. Strategies that combine a detention pond and ...

Reliability-Based Flood Management in Urban Watersheds Considering Climate Change Impacts

Abstract: Research has revealed the impacts of climate change on the hydrologic cycle. These impacts are intensified in the urban water system due to special characteristics of urban watersheds, such as a high percentage of impervious areas and the presence of a microclimate. A slight change in rainfall intensity and duration can cause severe floods, with a significant incremental increase in life and property losses. Therefore, it is a key issue to modify the urban watershed characteristics in a systematic way to deal with these probable changes. In this paper, a multicriteria optimization model is developed to select best management practices (BMPs) for flood management in urban watershed systems. The addressed criteria include maximizing reliability of the drainage system, as well as minimizing flood damages and BMP costs. A new reliability index for dealing with floods is suggested in this study that considers both severity and duration of flooding. The optimization model is solved using a two-stage mul...

Complex Adaptive Systems Approach to Simulate the Sustainability of Water Resources and Urbanization

Abstract: Urban water resources should be managed to meet conflicting demands for environmental health, economic prosperity, and social equity for present and future generations. While the sustainability of water resources can depend on dynamic interactions among natural, social, and infrastructure systems, typical water resource planning and management approaches are based on methodologies that ignore feedbacks and adaptations among these systems. This research develops and demonstrates a new complex adaptive systems approach to model the dynamic interactions among population growth, land-use change, the hydrologic cycle, residential water use, and interbasin transfers. Agent-based and cellular automaton models, representing consumers and policymakers who make land- and water-use decisions, are coupled with hydrologic models. The framework is applied for an illustrative case study to simulate urbanization and the water supply system over a long-term planning horizon. Results indicate that interactions amon...

Reservoir Operation for Simultaneously Meeting Water Demand and Sediment Flushing: Stochastic Dynamic Programming Approach with Two Uncertainties

Abstract: River bed materials are commonly removed and conveyed downstream. In this process, some sediments are deposited in reservoirs, causing a decrease in reservoir active storage capacity and thus its ability to meet water demand. Flushing is a sediment-release method operated from the bottom outlet gates that releases stored water to flush sediments. As a result, water shortages may occur after the flushing operation. Thus, it is important to develop a reservoir operation policy for time and volume release of sediment that meets water demand. Uncertainties in water and sediment inflows to the reservoir are also important issues that add to the complexity of such policies. This paper presents a stochastic dynamic programming (SDP) model with two uncertainties to determine the simultaneous optimal operation policies for meeting water demand and sediment flushing. To evaluate the capability of the SDP model with two uncertainties, four other operation policies are developed, and all five scenarios are ev...

Scenario-Based Robust Optimization of Regional Water and Wastewater Infrastructure

Abstract: Uncertainties facing water planners and designers include changes in demand resulting from community growth (temporal and spatial), per capita water use, public perceptions, and regulations One of the most powerful and intuitive ways to represent these uncertainties in the planning stage is to use scenarios A scenario represents a realization of the system’s random parameters Scenario-based analysis provides organizational flexibility by planning for multiple potential future scenarios, each of which may be, although is not necessarily, associated with a probability of occurrence In this study, a scenario-based multiobjective optimization model for robust optimal design of regional-scale water and wastewater infrastructure is presented The proposed methodology is demonstrated with an application to the planning of a decentralized water supply and reuse system for a new development area in metropolitan Tucson, where sustainable water supply is a significant issue

Operating Water Distribution Networks during Water Shortage Conditions Using Hedging and Intermittent Water Supply Concepts

Abstract: Population increase and requirements as well as water resource limitations reveal the necessity for the optimal operation of water distribution networks (WDNs), especially during shortage events. Because WDNs directly affect lifestyles, operational plans that take into account abnormal conditions are necessary. Under such circumstances, some possible solutions, such as transferring water from other basins or using recycled waters, may be inapplicable or insufficient, as continuous operation of WDNs would not be possible anymore. This paper proposes hedging or intermittent water supply as a contrasting way against a water shortage juncture. In this method of operation and in a specific time span during the operational period, the amount of water supplied to each consumer could be different even if their demands are equal. Thus, the selection of a policy that guarantees equity in supplying consumers’ demands has to be considered. In addition, supplying demands with sufficient pressure would promote ...

Design of Efficient Water Pricing Policies Integrating Basinwide Resource Opportunity Costs

Abstract: By ignoring the opportunity cost of water use, water is undervalued, which can lead to significant errors in investments and water allocation decisions. The marginal resource opportunity cost (MROC) varies in time and space, as resource availability, demands, and users’ WTP vary. This spatial and temporal variability can only be captured by basinwide hydro-economic models integrating water demands and environmental requirements, resources, infrastructure, and operational and institutional restrictions. This paper presents a method for the simulation of water pricing policies linked to water availability, and the design of efficient pricing policies that incorporate the basinwide marginal value of water. Two approaches were applied: priority-based simulation and economic optimization. The improvement in economic efficiency was assessed by comparing the results from simulation of the current system operation and the pricing schedule. The difference between the benefits for the simulated current mana...

Evaluating the impact of alternative hydro-climate scenarios on transfer agreements: Practical improvement for generating synthetic streamflows

Abstract: Utilities are increasingly considering the use of temporary water transfers to augment their supplies during periods of drought, an alternative that is often less expensive than expanding safe yields through new infrastructure. Understanding the volume and timing of transfers is important for developing contracts between buyer and seller and can be challenging due to the transient nature of drought, a situation complicated by the uncertainties associated with climate change. While transfer arrangements have received some attention in the literature, the effects of climate change on such agreements remain unexplored. This paper investigates these impacts using an improved method for developing new hydro-climate scenarios. A technique for producing stochastic time series of inflows is described, one which effectively replicates the autocorrelation present in the historic record. Unlike autoregressive (and similar) models that assume complete stationarity, the modified fractional Gaussian noise (mFGN...

Optimizing Watershed Management by Coordinated Operation of Storing Facilities

Abstract: Water storing facilities in a watershed are very often operated independently one to another to meet specific operating objectives, with no information sharing among the operators. This uncoordinated approach might result in upstream-downstream disputes and conflicts among different water users or inefficiencies in the watershed management when looked at from the viewpoint of an ideal central decision-maker. In this paper, the authors propose an approach in two steps to design coordination mechanisms at the watershed scale with the ultimate goal of enlarging the space for negotiated agreements between competing uses and improving the overall system efficiency. First, the multiobjective centralized solution is computed to assess the maximum potential benefits of a shift from a sector-by-sector to an ideal fully coordinated perspective. Then, the Pareto-optimal operating policies are analyzed to gain insight into suitable strategies to foster cooperation or impose coordination among the involved age...

Iterative Methodology of Pressure-Dependent Demand Based on EPANET for Pressure-Deficient Water Distribution Analysis

Abstract: Traditional water distribution simulations, known as demand-driven analysis (DDA), are normally analyzed under the assumption that nodal demands are known and satisfied. The DDA is valid under normal conditions and in design requirement. However, in situations such as pipe burst or pump outage, the outflows at nodes affected by low pressures will decrease. Therefore, network simulation under deficient pressure conditions using conventional DDA can cause large deviation from actual situations. The purpose of this paper is to analyze different compositions of nodal outflow, including volume-driven demand, pressure-dependent demand and leakage to simulate deficient network performance more realistically. An extension of the modeling package EPANET, which implements repetitive modifications to nodal outflows based on pressure-dependent demand formulations and leakage models (EPANET-MNO), is first developed. Then, a comparison is made between the respective performances of four different pressure-depen...

Development and Field Validation of a Burst Localization Methodology

Abstract: Reducing water loss through bursts is a major challenge throughout the developed and developing world. Currently burst lifetimes are often long because awareness and location of them is time- and labor-intensive. Advances that can reduce these periods will lead to improved leakage performance, customer service, and reduce resource wastage. In water-distribution systems the sensitivity of a pressure instrument to change, including burst events, is greatly influenced by its own location and that of the event within the network. A method is described here that utilizes hydraulic-model simulations to determine the sensitivity of potential pressure-instrument locations by sequentially applying leaks to all potential burst locations. The simulation results are used to populate a Jacobian matrix, quantifying the different sensitivities. This matrix may then be searched to identify different instrument locations to achieve required goals: maximising overall sensitivity to all potential events or selective sensitivity to events in different network areas. It is shown here that by searching this matrix to optimize such selective sensitivity, while minimising instrument numbers, it is possible to provide useful burst-localization information. Results are presented from field studies that demonstrate the practical application of the method, showing that current standard network models can provide sufficiently accurate quantification of differential sensitivities and that, once combined with event-detection techniques for data analysis, events can effectively be localized using a small number of instruments.

Centralized versus decentralized wastewater reclamation in the Houghton area of Tucson, Arizona.

Abstract: Reclaimed wastewater is increasingly important to satisfaction of water-sustainability objectives in water-short municipalities throughout the United States and particularly in the Southwest. Water reclamation and reuse present new challenges for urban planners, who now tend to consider renewable freshwater and reclaimed wastewater as unique parts of a single water resources portfolio. Efficiency objectives in geographically dispersed communities lead planners to explore the relative merits of centralized versus decentralized wastewater-treatment capacity when new construction is required. However, the complexity of the planning landscape—in which existing water distribution and sewerage capacities; geographic factors; and uncertainty in growth projections, energy cost, and even the sustainability of existing freshwater supplies contribute to plan selection—suggests that decision support methods can usefully supplement engineering judgment to find a near-optimal level of decentralization in facili...

Residential water conservation in Australia and California.

Abstract: In much of the western United States, reducing residential water use is a major source of water conservation, especially as population growth urbanizes agricultural land. Although estimates of the potential of conservation are useful, the experience of Australia provides a realistic target for residential water conservation. Although reliability of urban water use data is often questionable, it is clear that Australians use less water than Californians, with a similar climate, economy, and culture. Per capita usage is compared, and explanations for use differences are offered. If California had the same residential water use rates as Australia, it could have reduced gross urban water use by 2,600 GL (2.1 million acre-feet) in 2009 and potentially saved 1,800 GL (1.5 million acre-feet) for consumptive use by others. DOI: 10.1061/ (ASCE)WR.1943-5452.0000225. © 2013 American Society of Civil Engineers. CE Database subject headings: Water demand; Municipal water; Water use; Pricing; Australia; California. Author keywords: Water demand; Municipal water; Water use; Pricing; Australia; California.

Iterative Linearization Scheme for Convex Nonlinear Equations: Application to Optimal Operation of Water Distribution Systems

Abstract: Convex equations exist in different fields of research. As an example are the Hazen-Williams or Darcy-Weisbach head-loss formulas and chlorine decay in water supply systems. Pure linear programming (LP) cannot be directly applied to these equations and heuristic techniques must be used. This study presents a methodology for linearization of increasing or decreasing convex nonlinear equations and their incorporation into LP optimization models. The algorithm is demonstrated on the Hazen-Williams head-loss equation combined with a LP optimal operation water supply model. The Hazen-Williams equation is linearized between two points along the nonlinear flow curve. The first point is a fixed point optimally located in the expected flow domain according to maximum flow rate expected in the pipe (estimated through maximum flow velocities and pipe diameter). The second point is the calculated flow rate in the pipe resulting from the previous iteration step solution. In each iteration step, the linear coefficients are altered according to the previous step's flow rate result and the fixed point. The solution gradually converges closer to the nonlinear head-loss equation results. The iterative process stops once both an optimal solution is attained and a satisfactory approximation is received. The methodology is demonstrated using simple and complex example applications. DOI: 10.1061/(ASCE)WR.1943-5452.0000275. © 2013 American Society of Civil Engineers. CE Database subject headings: Optimization; Water distribution systems; Chlorine; Water supply. Author keywords: Convex; Optimization; Water distribution systems; Optimal operation; Successive linearization; Head loss.

Loop-by-Loop Cutting Algorithm to Generate Layouts for Urban Drainage Systems

Abstract: The design of urban drainage systems consists of solving two subproblems: (1) generating the layout and (2) sizing the sewers The latter includes pipe diameters, installation depths, and pumping facilities, all of which are significantly influenced by the layout configuration This work aims at introducing a method to solve the layout subproblem based on the graph theory For a given city, all possible sewer lines and manholes are considered for the sewer network so that an undirected looped graph is initially formed Next, an adaptive procedure entitled the loop-by-loop cutting algorithm is developed to create feasible sewer layouts from the base graph Using this algorithm, all constraints of the sewer layout subproblem are systematically handled By defining an objective function, the optimum layout is achieved by employing a simple genetic algorithm After the sewer layout is determined, the specifications for pipes and pumps are designed by using a discrete differential dynamic programming m

Extension of Parametric Rule with the Hedging Rule for Managing Multireservoir System during Droughts

Abstract: In contrast to most common methods used in optimal control of reservoir systems requiring a large number of decision variables, parametric rule can make a radical reduction in the number of...

Value of Information in the Design of Resilient Water Distribution Sensor Networks

Abstract: The ability to monitor the flow and how water transforms throughout water networks would greatly improve the management of those distribution systems. The sensor placement problem attempts to find the locations of monitoring devices that would optimally observe water quality and protect consumers from accidents and intrusions of contaminants. In some related critical scenarios, the absence of information about possible contamination events, including knowledge of the injection sources, contaminant types or mass, time of pollution, and the variability of water network input parameters, such as the nodal demands and the pipe roughness coefficients, raises several challenges that must be addressed by the sensor network design process. In this paper, the authors describe a stochastic parameterization and analysis of uncertainty for the design of sensor networks aimed at maximizing the probability of detection of accidents and intrusions in water distribution networks. A challenge with such an approach...

Bayesian Networks for Source Intrusion Detection

Abstract: Bayesian belief networks are graphical probabilistic analysis tools for representing and analyzing problems involving uncertainty. The problem of monitoring the propagation of a contaminant in a water distribution system can be represented by using Bayesian networks (BNs). The presented methodology proposes the use of BN statistics to estimate the likelihood of the injection location of a contaminant and its propagation in the system. A clustering method, previously developed by the authors, is first applied to formulate a simplified representation of the distribution system based on nodal connectivity properties. Given evidence from clusters, information is combined through probabilistic inference using BNs to find the most likely source of contamination and its propagation in the network. The conditional independence assumptions with the BNs allow efficient calculation of the joint probabilities and diagnostic and predictive queries (e.g., the most likely event given evidence or the probability ...

End-to-End Cyberinfrastructure for Decision-Making Support in Watershed Management

Abstract: Over the past decade, water-centric research has increasingly taken into consideration the interactions between the water cycle and the social, economic, and biogeophysical processes that drive watershed dynamics. In parallel, water management has made great strides in data sharing and collaborative modeling that support decision making through integrated planning and stakeholder involvement. Both research and management communities require data and simulation models that cover large spatial scales and workflows that enable investigations and decision making in real time with participation of multiple watershed actors. To efficiently accomplish their goals, these two communities are tapping into the capabilities of advanced cyberinfrastructure (CI) platforms that facilitate an understanding of watershed processes, knowledge management, visualization, interaction, and collaboration in multiple watershed science and engineering disciplines. This paper illustrates an implementation of an end-to-end C...

Systems Analysis Approach to the Design of Efficient Water Pricing Policies under the EU Water Framework Directive

Abstract: Economic theory suggests that water pricing can contribute to efficient management of water scarcity. The European Union (EU) Water Framework Directive (WFD) is a major legislative effort to introduce the use of economic instruments to encourage efficient water use and achieve environmental management objectives. However, the design and implementation of economic instruments for water management, including water pricing, has emerged as a challenging aspect of WFD implementation. This study demonstrates the use of a systems analysis approach to designing and comparing two economic approaches to efficient management of groundwater and surface water given EU WFD ecological flow requirements. Under the first approach, all wholesale water users in a river basin face the same volumetric price for water. This water price does not vary in space or in time, and surface water and groundwater are priced at the same rate. Under the second approach, surface water is priced using a volumetric price, while groun...

Pressure-Discharge Relations with Application to Head-Driven Simulation of Water Distribution Networks

Abstract: The pressure-discharge relation used in continuity equations is one of the most important components of hydraulic models based on head-driven simulation method, as it has a great impact on the accuracy of the results of these models. Several pressure-discharge relations have been proposed and used in head-driven simulation method, but there are no laboratory and field studies available regarding the accuracy and correctness of these relations. In this research a laboratory set up and a field investigation in some parts of a real water distribution network are used to collect the required data. Flow discharge data from different faucets, based on laboratory and field measurements, are used to compare the proposed pressure-discharge relationships. Furthermore, in this paper, a new pressure-discharge relation is proposed for volumetric and human-based demands that is more reasonable than some previous relations and can be used in pressure-dependent models.

Estimating Maximal Annual Energy Given Heterogeneous Hydropower Generating Units with Application to the Three Gorges System

Abstract: A hierarchical optimization method is presented for an assessment of the potential maximum energy output of the Three Gorges Project and Gezhouba cascade hydropower stations in China. The optimization incorporates a detailed description of daily load dispatching among different types of hydropower units. The optimization method is divided into three levels to render feasible the computation of the global optimization problem. In levels 1 and 2, a genetic algorithm is applied to optimize discharge and water head distribution between the upstream and downstream reservoirs. Level 1 selects the water levels at the beginning of each month in a year. Level 2 selects the water levels at the beginning of each day in a month. Level 3 solves a linear programming problem for allocation of water among the heterogeneous types of hydropower generation. Hydrological data of the years 2004 and 2005 are used to perform an optimized power generation process within the operating rules. The maximal annual energy prod...

Relationship between Water Withdrawals and Freshwater Ecosystem Water Scarcity Quantified at Multiple Scales for a Great Lakes Watershed

Abstract: Even in relatively water-rich regions, withdrawal and consumption of water has the potential to create instream freshwater ecosystem water scarcity, especially at seasonal and local scales

Temperature and Precipitation Trends in Lebanon’s Largest River: The Litani Basin

Abstract: This study deals with the historical hydro-climatological watershed characteristics of the Litani basin located in Lebanon, east of the Mediterranean Sea, during 1900–2008. The basin is divided into two distinct sub-basins. The Upper Litani Basin (ULB) is mostly dominated by mountainous geophysical features and the Lower Litani Basin (LLB) is closer to the Mediterranean coast. Monthly and annual temperature and precipitation data were generated from different sources, including global gridded data, satellite data, and local station data. Because long-term runoff records were not available, previously generated monthly synthetic runoff data were employed. Temperature and precipitation trends were investigated using the Mann-Kendall and Sen Slope nonparametric trend tests. The mean annual and monthly runoff were subsequently correlated with temperature and precipitation variations using a multiple linear regression approach. The results show that between 1900 and 2008, the whole Litani basin, includ...