Showing papers in "Journal of Water Resources Planning and Management in 2014"

Urban Water Demand Forecasting: Review of Methods and Models

Abstract: This paper reviews the literature on urban water demand forecasting published from 2000 to 2010 to identify methods and models useful for specific water utility decision making problems. Results show that although a wide variety of methods and models have attracted attention, applications of these models differ, depending on the forecast variable, its periodicity and the forecast horizon. Whereas artificial neural networks are more likely to be used for short-term forecasting, econometric models, coupled with simulation or scenario-based forecasting, tend to be used for long-term strategic decisions. Much more attention needs to be given to probabilistic forecasting methods if utilities are to make decisions that reflect the level of uncertainty in future demand forecasts.

Automated Detection of Pipe Bursts and Other Events in Water Distribution Systems

Abstract: This paper presents a new methodology for the automated near-real-time detection of pipe bursts and other events that induce similar abnormal pressure/flow variations (e.g., unauthorized consumptions) at the district metered area (DMA) level. The new methodology makes synergistic use of several self-learning artificial intelligence (AI) techniques and statistical data analysis tools, including wavelets for denoising of the recorded pressure/flow signals, artificial neural networks (ANNs) for the short-term forecasting of pressure/flow signal values, statistical process control (SPC) techniques for short- and long-term analysis of the pipe burst/other event-induced pressure/flow variations, and Bayesian inference systems (BISs) for inferring the probability of a pipe burst/other event occurrence and raising corresponding detection alarms. The methodology presented here is tested and verified on a case study involving several DMAs in the United Kingdom (U.K.) with both real-life pipe burst/other eve...

Nonparametric Benchmarking of Japanese Water Utilities: Institutional and Environmental Factors Affecting Efficiency

Abstract: Although the Japanese water sector is economically and socially important, few empirical studies are available to help analysts and policy-makers understand the performance patterns in the industry. This study applies data envelopment analysis to 5,538 observations of 1,144 utilities that supplied drinking water between 2004 and 2007. With a comprehensive census of utilities, the present study controls for many factors affecting efficiency: region, prefecture, ownership/governance, water source, vertical integration (purchased or produced alone), water or integrated system, production, treatment, transport and distribution of water), peak factor, per capita consumption, customer density, water losses, monthly water charge, outsourcing, subsidies, gross prefecture product, and time. Thus, this study derives comprehensive conclusions regarding efficiency patterns in Japan. The analysis finds that the average level of inefficiency (weighted by volume) is 57% in the constant return to scale model, but...

Water Network Sectorization Based on Graph Theory and Energy Performance Indices

Abstract: This paper proposes a new methodology for the optimal design of water network sectorization, which is an essential technique for improving the management and security of multiple-source water supply systems. In particular, the network sectorization problem under consideration concerns the definition of isolated district meter areas, each of which is supplied by its own source (or sources) and is completely disconnected from the rest of the water system through boundary valves or permanent pipe sectioning. The proposed methodology uses graph theory principles and a heuristic procedure based on minimizing the amount of dissipated power in the water network. The procedure has been tested on two existing water distribution networks (WDNs) (in Parete, Italy and San Luis Rio Colorado, Mexico) using different performance indices. The simulation results, which confirmed the effectiveness of the proposed methodology, surpass empirical trial-and-error approaches and offer water utilities a tool for the desi...

Improved Dynamic Programming for Hydropower Reservoir Operation

Abstract: The writers propose a successive improved dynamic programming (SIDP) algorithm for hydropower reservoir operation based on an analysis of concavity, complementarity, and monotonicity of hydropower problems. For single-period hydropower generation, storage and release have diminishing marginal contributions to hydropower generation (i.e., concavity), and there is also a complementary effect between storage and release (i.e., release becomes more productive in accordance with increasing storage). For multiple-period hydropower generation, the complementarity influences the concavity of the objective function and the monotonicity of operation decisions, and is the major cause of complexity in hydropower operation. With mathematical derivations, the writers propose a concave approximation to the hydropower generation function and a SIDP algorithm for hydropower reservoir operation. The efficiency of SIDP is demonstrated with two hypothetical case studies of long-term hydropower scheduling, which shows...

Battle of the Water Networks II

Abstract: The Battle of the Water Networks II (BWN-II) is the latest of a series of competitions related to the design and operation of water distribution systems (WDSs) undertaken within the Water Distribution Systems Analysis (WDSA) Symposium series. The BWN-II problem specification involved a broadly defined design and operation problem for an existing network that has to be upgraded for increased future demands, and the addition of a new development area. The design decisions involved addition of new and parallel pipes, storage, operational controls for pumps and valves, and sizing of backup power supply. Design criteria involved hydraulic, water quality, reliability, and environmental performance measures. Fourteen teams participated in the Battle and presented their results at the 14th Water Distribution Systems Analysis conference in Adelaide, Australia, September 2012. This paper summarizes the approaches used by the participants and the results they obtained. Given the complexity of the BWN-II problem and the innovative methods required to deal with the multiobjective, high dimensional and computationally demanding nature of the problem, this paper represents a snap-shot of state of the art methods for the design and operation of water distribution systems. A general finding of this paper is that there is benefit in using a combination of heuristic engineering experience and sophisticated optimization algorithms when tackling complex real-world water distribution system design problems.

Identifying Residential Water End Uses Underpinning Peak Day and Peak Hour Demand

Abstract: Accurate and up-to-date peak demand data are essential to ensure that future mains water supply networks reflect current usage patterns and are designed efficiently from an engineering, environmental, and economic perspective. The aim of this paper was to identify the water end-uses that drive peak day demand and to examine their associated hourly diurnal demand patterns based on over 18 months of water consumption data obtained from high-resolution smart meters installed in 230 residential properties across South East Queensland, Australia. Peak day (PD) to average day (AD) ratios between 1 and 1.5 were driven by both external and internal end-uses. However, as the PD:AD ratio increased above 1.5, demand was driven largely by external water usage (i.e., lawn and garden irrigation). Peak hour ratios (i.e., PHPD:PHAD) ranged from 1.3 to 3.0 for the four peak demand days. At the end-use level, the individual end-use category PHPD:PHAD ratios were in the range of 0.7–3.3 for all end-uses, with the ex...

Optimization of Conventional Rule Curves Coupled with Hedging Rules for Reservoir Operation

Abstract: As a common approach to reservoir operating policies, water levels at the end of each time interval should be kept at or above the rule curve. In this study, the policy is captured using rationing of the target yield to reduce the intensity of severe water shortages. For this purpose, a hybrid model is developed to optimize simultaneously both the conventional rule curve and the hedging rule. In the compound model, a simple genetic algorithm is coupled with a simulation program, including an inner linear programming algorithm. In this way, operational policies are imposed by priority concepts to achieve the optimal water allocation and the target storage levels for reservoirs. As a case study, a multipurpose, multireservoir system in southern Iran is selected. The results show that the model has good performance in extracting the optimum policy for reservoir operation under both normal and drought conditions.

Complex Adaptive Systems Framework to Assess Supply-Side and Demand-Side Management for Urban Water Resources

Abstract: The availability of water resources in many urbanizing areas is the emergent property of the adaptive interactions among consumers, policy, and the hydrologic cycle. As water availability becomes more stressed, public officials often implement restrictions on water use, such as bans on outdoor watering. Consumers are influenced by policy and the choices of other consumers to select water-conservation technologies and practices, which aggregate as the demand on available water resources. Policy and behavior choices affect the availability of water for future use as reservoirs are depleted or filled. This research posited urban water supply as a complex adaptive system (CAS) by coupling a stochastic consumer demand model and a water supply model within an agent-based modeling (ABM) framework. Public officials were simulated as agents to choose water conservation strategies and interbasin transfer strategies, and consumers were simulated as agents, influenced by various conservation-based programs to...

Dealing with Uncertainty in Water Distribution System Models: A Framework for Real-Time Modeling and Data Assimilation

Abstract: Water distribution system (WDS) models may improve system control when applied using real-time data, and in doing so, help meet consumer and regulatory demands. Such real-time modeling often overlooks the multiple sources of system uncertainty that cascade into model forecasts and affect the identification of robust operational solutions. This paper considers key uncertainties in WDS modeling and reviews promising approaches for uncertainty quantification and reduction in the modeling cascade from calibration, through data assimilation, to model forecasting. An uncertainty framework exemplifying how such methods may be applied to propagate uncertainty through the real-time control process is outlined. Innovative methods to constrain uncertainty when the time-horizon and data availability limit such thorough analysis are also discussed, alongside challenges that need to be addressed to incorporate uncertain information into the control decision. Further work evaluating the value of these methods in...

Cost-Benefit Analysis for Hydropower Production in Water Distribution Networks by a Pump as Turbine

Abstract: The use of microhydroelectric plants in urban pipe networks, based on the combination of a pump as turbine (PAT), two regulating valves, and two pressure meters, is proposed along with simple automation rules. Its economic benefit is tested on a small pipe network, where the network geometry as well as the demand coefficient variation in time and space have been inferred from previously collected data and existing analysis. A similar analysis has been also carried out for different scenarios in which the reduction of pipe installation cost due to a diameter reduction is compared with the increased benefit in energy production. The case study shows that a small increment of the pipe installation cost, with respect to the minimum required by the nodes minimum pressure, can lead to a larger benefit for energy production.

Graph-theoretic approach and sound engineering principles for design of district metered areas

Abstract: The design of district metered areas (DMAs) in existing water distribution networks, especially in urban areas, involves a high number of decision variables, and the effects of implementing them in districts have to be evaluated in order not to affect the quality of the service to customers. A new methodology for designing a given number of districts in looped water distribution networks is proposed here. It is based on graph theory and takes into account some important DMA design criteria: the maximum and minimum size recommended for a district, the connectedness of each district to the water supply source, and the absence of links between the districts. Therefore, it allows the creation of DMAs that are independent from each other. A recursive bisection procedure has been applied to create districts, while an algorithm for graph traversal has been used to verify whether each district can be reached from the water source and connectivity between the nodes. The successful application of the propos...

Optimal Location of PRVs and Turbines in Water Distribution Systems

Abstract: Pressure reducing valves (PRVs) are often used to manage pressure and reduce losses in water distribution systems (WDS). Different approaches are available in the literature on how to locate and set the PRVs in order to maximize their effectiveness and minimize water losses. The available methodologies minimize the mean square difference between the actual and the target pressure at each node. Since the excess head can be used also to generate hydropower by using turbines and/or pumps as turbines (PATs), a different objective function could be suggested to maximize energy production. Consequently, a comprehensive analysis will be developed in the paper which highlights the differences between the preexisting approach and the suggested one, in terms of device location, pressure reduction, and recoverable energy. Numerical simulations showed that minimizing pressure may also affect the production of energy, while maximizing the energy production itself could be an attractive alternative, leading to ...

Reliability Indicators for Water Distribution System Design: Comparison

Abstract: When designing a water distribution system (WDS), it is imperative that the reliability of the network is taken into consideration. It is possible to directly evaluate the reliability of a WDS, although the calculation processes involved are computationally intensive and thus undesirable for some state-of-the-art, iterative design approaches (such as optimization). Consequently, interest has recently grown in the use of reliability indicators, which are simpler and faster to evaluate than direct reliability methods. In this study, two existing reliability indicators, the Todini resilience index and entropy for WDS, are examined by analyzing their relationships with different subcategories of reliability, namely the mechanical (network tolerance to pipe failure) and hydraulic reliability (network tolerance to demand change). The analysis is performed by generating comparable solutions through multiobjective optimization of cost against the chosen indicators using the well known Anytown WDS benchmar...

Research Database of Water Distribution System Models

Abstract: Since the 1960s, researchers have continued to develop new methodologies and algorithms in support of the planning, design, and management of water distribution systems. While initial research focused on modeling the hydraulics of such systems, the 1980s gave rise to additional research focus on water quality issues. More recent research has expanded into issues of system reliability and resilience, energy management, and sensor and chlorine booster station placement. In most cases, researchers have relied on either hypothetical water distribution systems or a handful of actual systems for use as benchmark test systems. Some of the more widely used actual systems include the New York tunnel system and the Hanoi water distribution system. This paper describes the development of a database of several water distribution systems synthesized from a statewide database of systems originally developed by the Kentucky Infrastructure Authority. The developed models include both small and medium networks, as...

Optimal Hedging Rules for Reservoir Flood Operation from Forecast Uncertainties

Abstract: This paper develops optimal hedging rules for reservoir flood control operation under hydrological uncertainty using hydroeconomic and mathematical analysis. The capacity to convey flood flows is sometimes a scarce resource. Hedging for flood operations uses reservoir storage to allocate the expected flood-safety margin (EFSM, i.e., the gap between expected flood volume and flood-conveyance capacity) optimally between present and future periods. Optimal flood-operation hedging falls into three cases, namely, (1) for large expected floods, all flood storage and almost all channel-conveyance capacity are used in the current period to cope with the current, more certain, and urgent flood risk; (2) for medium expected floods, the available EFSM is balanced between the current and future periods, but a larger portion of the total EFSM remains allocated to the current stage; and (3) for small expected floods, the future stage receives greater EFSM allocation by keeping reservoir space empty in the curre...

Multiperiod Planning of Water Supply Infrastructure Based on Scenario Analysis

Abstract: Long-range infrastructure planning is fraught with uncertainties. Population growth may occur faster or slower than expected, regulations may change, and public sentiment can shift. In the face of these uncertainties, water system managers must plan for large infrastructure investments and the questions about when it is desirable to invest in infrastructure and what is the appropriate infrastructure component size to meet growing demands. One of the most powerful and intuitive ways to incorporate uncertainties is to use scenarios that represent plausible futures. Scenario-based planning is gaining acceptance in the water resources community. Preparing for a range of possible futures provides flexibility and adds robustness to the system so it can respond to uncertain events at reasonable costs while maintaining community confidence in their utilities. In this paper, novel scenario-based planning and optimization approaches are presented for the optimal design of regional-scale water supply infrast...

Planning the Optimal Operation of a Multioutlet Water Reservoir with Water Quality and Quantity Targets

Abstract: The integration of quality and quantity issues in the management of water resources systems is key to meet society’s long-term needs for freshwater while maintaining essential ecological services and economic benefits. Current water management practices are mostly targeted towards quantitative uses, and quality is usually addressed separately as an independent problem. One of the reasons for the lack of integration lies in the inadequacy of optimization techniques nowadays available to cope with the large, distributed, simulation models adopted to characterize the coupled ecological and biochemical processes in water bodies. In this paper we propose a novel approach based on the conjunctive use of a batch-mode Reinforcement Learning algorithm and a one-dimensional (1D) coupled hydrodynamic-ecological model to design the optimal operation of a multipurpose water reservoir accounting for both quantity and quality targets. We consider up to five operating objectives, including both in-reservoir and d...

Robustness-Based Design of Water Distribution Systems

Abstract: Robustness is generally defined as an ability of a system to maintain its function under a defined set of disturbances. To introduce robustness to the water distribution systems (WDSs) design, chance constrained, or so-called reliability-based models have been formulated. Under variations in system parameters, such as nodal demands and pipe roughness, system reliability is generally measured as the probability that the stochastic nodal pressures will be higher than an allowable minimum pressure limit. However, chance constraints may not be the best formulation to improve system robustness because it focuses on the likelihood of failure under a specified set of conditions rather than developing a solution that consistently provides adequate service. In addition, the reliability-based design requires defining the demand condition, its probability distribution and its statistics, which are not straight forward in practice. To address these difficulties, a robustness index that limits the range of the...

Evaluating the Performance of Urban Water Utilities: Robust Nonparametric Approach

Abstract: This paper empirically analyzes the efficiency of urban water utilities using state-of-the-art methodology combining data envelopment analysis (DEA) and a two-stage double bootstrap procedure. In the first stage, robust efficiency estimates are obtained with an improved DEA analysis. In the second stage, a truncated regression model and a double bootstrap procedure are used to estimate the effect of a set of environmental variables on unbiased DEA estimates. The findings suggest that the efficiency scores obtained after bias correction are significantly different to the original efficiency estimates. The results also show the existence of a significant relation between efficiency and several environmental variables including the proportion of water sourced from groundwater, customer density, and residential consumption.

Methodology for Comparing Evolutionary Algorithms for Optimization of Water Distribution Systems

Abstract: In recent years, a number of evolutionary algorithms have been proposed for optimizing the design and operation of water distribution systems (WDSs). These evolutionary algorithms include genetic algorithms, ant colony optimization, particle swarm optimization, the shuffled leaping frog algorithm, and differential evolution. Although there have been some comparisons made of the performance of the various algorithms, very few of these comparisons have been carried out in a completely rigorous manner. The main aim of this paper is to introduce a methodology for the rigorous comparison of various algorithms for the optimum design of water distribution systems. The methodology involves comparing the various algorithms in terms of (1) the best solution obtained; (2) the speed of convergence; and (3) the spread and consistency of the solutions obtained over a number of random starting seeds and numbers of evaluations. As a demonstration of the methodology, the techniques of genetic algorithms (GA), part...

Predicting the Timing of Water Main Failure Using Artificial Neural Networks

Abstract: Effective management of aging water distribution infrastructure is essential for preserving the economic vitality of North American municipalities. Historical failures within Scarborough, Ontario, Canada, reveal a seasonal pattern to water main failures, with the majority of failures occurring during the very cold winter months. Extensive installation of cement mortar lining and cathodic protection have extended the life span of aging water mains and reduced escalating failure rates. Artificial neural networks are found to be capable of predicting the time to failure for individual pipes using a range of pipe-specific attributes, including diameter, length, soil type, construction year, and the number of previous failures. The developed models have correlation coefficients ranging from 0.70–0.82 on instances reserved for evaluating predictive performance and have utility on an asset-by-asset basis when planning water main inspection, maintenance, and rehabilitation. Simulated failure scenarios ind...

Reliability Assessment for Water Supply Systems under Uncertainties

Abstract: Reliability assessment of water supply systems (WSSs) is an important aspect of WSS planning and operations. Traditionally, WSS reliability involves the comparison of hydraulics (e.g., pressure or available water volume) and water quality (e.g., residual chlorine) parameters with their desired minimum level of service under various emergency loading conditions. To compute hydraulic dependent parameters (e.g., pressures, flow), different algorithms solve continuity and energy equations expressed in terms of certain independent parameters (e.g., roughness parameters and nodal demands) with certainty. Similarly, transport equations expressed in terms of different quality parameters are solved deterministically to compute water quality dependent parameters (e.g., residual chlorine). However, it is extremely challenging, even impossible, to estimate network-independent parameters with certainty. Therefore, estimated dependent parameters based on semiquantitative information bear uncertainty, which lead...

Multiobjective Optimization for Improved Management of Flood Risk

Abstract: Effective flood risk management requires consideration of a range of different mitigation measures. Depending on the location, these could include structural or non-structural measures as well as maintenance regimes for existing levee systems. Risk analysis models are used to quantify the benefits, in terms of risk reduction, when introducing different measures; further investigation is required to identify the most appropriate solution to implement. Effective flood risk management decision making requires consideration of a range of performance criteria. Determining the better performing strategies, according to multiple criteria can be a challenge. This paper describes the development of a decision support system that couples a multi-objective optimisation algorithm with a flood risk analysis model and an automated cost model. The system has the ability to generate potential mitigation measures that are implemented at different points in time. It then optimises the performance of the mitigation measures against multiple criteria. The decision support system is applied to an area of the Thames Estuary and the results obtained demonstrate the benefits multiobjective optimisation can bring to flood risk management.

Bargaining Models for Optimal Design of Water Distribution Networks

Abstract: Optimal design of water distribution networks (WDN) involves an evaluation of both consumers’ pressure benefits and investors’ economic objectives. The aforementioned objectives often conflict, so finding the optimal solution for one of those objectives reduces the other objective’s utility. In such situations, there are many nondominated solutions, each solution denoting an alternative that cannot be preferred over another in terms of both objectives. Thus, an appropriate alternative to fulfill both objectives and satisfy decision makers’ criteria and meet the design purposes within a desirable range necessitates the use of bargaining models that are called conflict-resolution models. This paper considers two urban WDN optimization design problems having different objectives, including initial costs and hydraulic performance improvement of the network by satisfying given hydraulic constraints. First, a set of alternatives are drawn out by a fast messy genetic algorithm (FMGA), then the appropriat...

Accounting for Phasing of Construction within the Design of Water Distribution Networks

Abstract: The traditional optimization approach for water distribution mains is that of considering a single design scenario with prefixed nodal demands representing the peak values at the end of the life cycle of the construction. Instead, this paper presents a different approach for the design of water distribution mains aimed at considering the phasing of construction. It makes it possible to identify, on prefixed time steps or intervals (for instance 25 years), the upgrade of the construction rendering the network able to satisfy, during the expected life of the system, growing nodal demands related to the increment in the population served. To show the benefits of this approach in comparison to using a single design flow, an optimization methodology, aimed at introducing new pipes in the network as needed at each time step, was set up and applied to a simple case study, where two different scenarios were considered concerning the growth of the network. Results showed that this approach is able to yield...

Optimal Real-Time Operation of Multipurpose Urban Reservoirs: Case Study in Singapore

Abstract: The sustainable urban water management paradigm is based on the idea that water supply, storm water drainage, and wastewater disposal are interrelated resources that can increase the sustainability at the urban scale. In this context, the construction of reservoirs mainly fed by storm water and operated for drinking supply purposes can be demonstrated to achieve long-term sustainability objectives. However, the operational management of reservoirs located in urban areas faces a number of challenges due to the high hydraulic efficiency of urban catchments, i.e., short time of concentration, increased runoff rates, and losses of infiltration and baseflow. With the purpose of discussing the best alternatives to deal with these extreme hydrological features, this article analyzes the performance of offline and online operation, based on stochastic dynamic programming and deterministic model predictive control. Moreover, a quantitative assessment of the role of the hydro-meteorological information avai...

Optimal Operation of Large-Scale Cascaded Hydropower Systems in the Upper Reaches of the Yangtze River, China

Abstract: In recent decades, there has been a rapid rate of development of hydropower in China. The unprecedented rate of expansion, development scale, and large numbers of hydropower plants have posed a challenge to the operation of large-scale cascaded hydropower systems (OLCHSs), which has become one of the most important factors in ensuring the security and economic operation of the power grid in China. In this paper, a long-term optimal operation model is developed for the purpose of maximizing the total generated energy of cascaded hydropower plants. To solve the OLCHS problem effectively, an elite-guide particle swarm optimization (EGPSO) algorithm is proposed in this paper. An external archive set, which can preserve elite solutions during the evolution process, is employed to provide flying directions for particles. Since the OLCHS problem is a high-dimensional, nonlinear, multistage, and stringent constraint optimal problem, the proposed algorithm introduces three new innovations: a layer-partitio...

Reservoir Management Optimization for Basin-Wide Ecological Restoration in the Connecticut River

Abstract: Evidence from ecological studies suggests that the alteration of river flows downstream of reservoirs can threaten native aquatic ecosystems and the services they offer. Innovative revisions to water management practices are required to improve the health of aquatic species while maintaining the benefits from current infrastructure projects. The impacts of individual reservoir operations on ecosystem vitality are often masked by the uncoordinated and compounding influences of several impoundments upstream, undermining the examination of environmental impacts from particular reservoirs in a large watershed system. This paper presents a large-scale optimization model that investigates the value of coordinated reservoir management practices for ecological benefits in a large watershed with several major reservoir systems operating for a range of management objectives. An application of the model is presented for the Connecticut River watershed, the largest river basin in New England and one of the mo...

Frequency Response Diagram for Pipeline Leak Detection: Comparing the Odd and Even Harmonics

Abstract: Pipeline leak detection using hydraulic transient analysis is a relatively new detection technique. For single pipeline systems, recent work has led to two different approaches for determining leak parameters based on leak-induced patterns displayed in a pipeline’s frequency response diagram (FRD). The major difference between the two techniques is that one uses the leak-induced pattern within the odd harmonics of an FRD, while the other one uses the leak-induced pattern at the even harmonics. In order to compare and contrast the two approaches, the current research analyses the relationship between the characteristics of the leak-induced patterns and the parameters of the pipeline system. A dimensionless analysis, based on hydraulic impedance, is adopted to simplify the equations. The amplitudes of leak-induced patterns at both the odd and even harmonics in the FRD are found to be dependent on a critical parameter: the dimensionless steady-state valve impedance, ZV*. The value of ZV* is dependent...