Water Distribution System Model Research Articles

Using 3D Printing for Teaching and Outreach

The water industry is a valuable and often overlooked asset to a functioning, successful society. Water utilities have dreams and nightmares about the communities they serve touring their treatment plants. To educate and benefit the public, consider using three‐dimensional (3D) printing to create models of water distribution and treatment systems.

The Hourly Peak Coefficient of Single-Family and Multi-Family Buildings in Poland: Support for the Selection of Water Meters and the Construction of a Water Distribution System Model

Taking care of water resources and minimizing water losses in water supply networks requires a broad approach to identifying and neutralizing operational problems. The correct selection of water meters to minimize apparent losses requires knowledge of the characteristic flows that may occur in the facility to which water is supplied. The research aimed to develop tools in the form of mathematical models and water consumption curves along with hourly water consumption coefficients to facilitate the process of selecting water meters for engineers and creating computer models of water supply systems. The research involved monitoring the flow of 76 single-family and multi-family buildings in four towns in Poland, followed by data analysis and development of tools supporting the selection of water meters and the construction of computer models of water distribution networks. High correlation coefficients of the studied variables indicate the results’ usefulness. Four models were developed to determine the maximum flow values in multi-family buildings (three models) and single-family buildings (one model) in the range of water meter diameters DN15-DN40. Characteristics of the average hourly peak coefficient (HPC) values were also developed, along with the range of changes in HPC values for single-family and multi-family buildings.

AWWA Library

This is an abridged excerpt from chapter 1 of Handbook for Water Distribution System Model Calibration, first edition (catalog No. 20854). The book is available from the AWWA Store (www.awwa.org/model-calibration).

High pH and chloramine suppress nontuberculous mycobacterial growth in a model water distribution system

This study reports the importance of maintaining a high pH and/or chloramine concentrations in water distribution system to supress the growth of nontuberculous mycobacteria (NTM) - a group containing some opportunistic pathogens. Four sets of reactor systems, each containing three reactors connected in series, were operated at three different feed water pH values (7.6, 8.4, and 9.0) and two different chloramine concentrations (2.6 and 3.8 mg/L). Altogether, 44 operational taxonomic units of NTM were identified. The NTM species Mycobacterium chelonae, M. europaeum, M. gordonae, M. stephanolepidis, M. llatzerense, M. lentiflavum, and M. kyorinense were detected in the majority of the samples. Among them, M. chelonae was highly dominant NTM species in majority of the tested samples. The NTM populations were in the range of 8.83E+ 01–6.30E+ 05 gene copies/mL. Higher relative abundances of NTM were noted in reactors containing higher chloramine residuals, but the number of NTM and total bacterial population increased with the decreasing chloramine concentration, under low pH (<8.4) and under nitrifying conditions. This study underscores the benefits of maintaining high pH in the feed as it not only increases the chloramine stability, but also suppresses the bacterial growth including NTM.

Efficient Operation of Integrated Electrical-Water System for Wind Power Accommodation

This paper investigates the operation of an integrated electrical-water system for wind power accommodation. The efficient operation can be considered as how well to handle the binary variables in a water distribution system (WDS) model. The optimization problem of WDS is NP-hard, and it often takes hours to find the optimal solution. Since wind power varies in minutes, long computation time may hinder the WDS from being fully used by power system to deal with the wind power fluctuation and uncertainties. This paper develops a three-step optimization model to answer the challenges of the WDS optimization problem. The solution hinges on the calculation of the binary variable values in advance. The first step is to construct a linear power-WDS co-optimization (LPWCO) model to find the optimal electrical demand of WDS. The second step develops a tank flow allocation based method and a greedy-based algorithm to determine the binary variable values of WDS. This allows the WDS optimization model to be efficiently solved by commercial solvers in the third step. The proposed three-step model converts the NP-hard optimization problem of WDS into a polynomial-time problem which can be solved quickly. This allows the wind power system to leverage the energy flexibility provided by WDS in the real-time operation. Results of case study show that, compared with existing methods, the proposed method can reduce the wind power curtailment and the operation cost by about 55% and 53%. More importantly, the solution time is reduced dramatically from hours to seconds, suitable for practical application.

Random Walk Particle Tracking to Model Dispersion in Steady Laminar and Turbulent Pipe Flow.

To accurately model a two-dimensional solute transport in drinking water pipes and determine the effective dispersion coefficients for one-dimensional water quality models of water distribution systems, a random walk particle tracking approach was developed to analyze the advection and dispersion processes in circular pipes. The approach considers a solute particle's two-dimensional random movement caused by molecular or turbulent diffusion and associated velocity profile, and can simulate any mixing time and accurately model the longitudinal distribution of the solute concentration. For long mixing times, the simulation results agreed with a previous analytically derived solution. For turbulent flow conditions, simulations showed that the longitudinal dispersion of the solute is very sensitive to the utilized cross-sectional velocity profiles. This approach is easy to implement programmatically and unconditionally stable. It can predict the mixing characteristics of a pipe under various initial and boundary conditions.

A Conceptual model of mixed-integer linear programming water distribution system

Water is a basic part of our daily lives, as such effective water supply is of paramount importance. Thus, as a result of the rise in population size and water shortage there is the need for proper, suitable and optimal utilization of water resources to efficiently be distributed among the populace. The proper allocation and distribution of water in the field of network planning need to be modelled through mathematical parameters for objective of water distribution system. This mathematical approach requires of solving an optimization problem based on multi-objective function subjected to certain constraints of mixed integer linear programming objective function which is proportional to the cost of the water distribution network. This study present a conceptual model of multi-objective optimization proposed for determination of design parameters of water distribution system by considering the significant number of constraints, decision variables, cost and reliability objective functions. The model was proposed to solve the reliability problem of water production and reduce the design and operational costs.

Pressure dependent analysis in premise plumbing system modeling.

Modeling premise plumbing systems requires accurate treatment of fixture-specific pressure and flow rate relationships. Each fixture in a building may experience different flow rates based on variable service pressure, its unique pressure-flow behavior, and demands throughout the building. Unique experimentally derived pressure-flow parameters for four faucets, a shower/tub fixture, and toilet were developed. The Water Network Tool for Resilience (WNTR) was also used to explore the impact of premise plumbing systems on water distribution systems through two simple skeletonization cases. Minimum pressures for nodes in water distribution system models that represent demand aggregated premise plumbing systems will likely be non-zero and must capture additional pressure drop or elevation differences at the building scale and associated components, such as water meters or backflow preventers. Results showed that flow rates are impacted by pressure in these systems in complex ways, and usage and system characteristics must be considered to be modeled accurately.

Simpler Is Better—Calibration of Pipe Roughness in Water Distribution Systems

Hydraulic models of water distribution systems (WDSs) need to be calibrated, so they can be used to help to make informed decisions. Usually, hydraulic model calibration follows an iterative process of comparing the simulation results from the model with field observations and making adjustments to model parameters to make sure an acceptable level of agreement between predicted and measured values (e.g., water pressure) has been achieved. However, the manual process can be time-consuming, and the termination criterion relies on the modeler’s judgment. Therefore, various optimization-based calibration methods have been developed. In this study, three different optimization methods, i.e., Sequential Least Squares Programming (SLSQP), a Genetic Algorithm (GA) and Differential Evolution (DE), are compared for calibrating the pipe roughness of WDS models. Their performance is investigated over four different decision variable set formulations with different levels of discretization of the search space. Results obtained from a real-world case study demonstrate that compared to traditional engineering practice, optimization is effective for hydraulic model calibration. However, a finer search space discretization does not necessarily guarantee better results; and when multiple methods lead to similar performance, a simpler method is better. This study provides guidance on method and formulation selection for calibrating WDS models.

Modeling of Water Distribution System Based on Ten-Minute Accuracy Remote Smart Demand Meters

In the process of water distribution system modeling, nodal demands have been deemed to be the most significant input parameters causing uncertainties. Conventionally, users of the same type are assigned the same demand pattern, which does not reflect the variability in demand patterns. In Hefei City, a lot of remote smart demand meters were installed in recent years, providing real-time water consumption data for different water user sites. In this study, the water consumption data based on 10 min accuracy were collected and used in the established EPANET model of the study area. A 48 h simulation, including workdays and weekends, was carried out, and each node’s base demand and demand pattern were accurately calculated according to the remote data. The results show that the accuracy of the model has met the modeling criteria (less than 2 m for all pressure monitoring points), and there is no need to calibrate the nodal demand. The established offline hydraulic model can better reflect the water consumption characteristics of each type of user and has revealed the significant influence of secondary water supply systems.

Evaluation of Hydraulic Performances Modeling of Water Distribution Systems and Physicochemical Water Quality Analysis, in the Case of Dangila Town, Amhara Region, Ethiopia

Evaluation of Hydraulic Performances Modeling of Water Distribution Systems and Physicochemical Water Quality Analysis, in the Case of Dangila Town, Amhara Region, Ethiopia

Comparing alternative PDA solvers with EPANET

Abstract This work compares several alternative methods of pressure-driven analysis (PDA) implemented within the code base of the EPANET water distribution system modeling software. The resulting code includes a direct method, the original and a newly modified version of the inverse method currently used by EPANET 2.2, and two recently published methods (the global gradient approach-based PDA and the active set method). The latter four methods solve PDA problems using an inverse flow–pressure relationship, whereas the direct method uses the original relationship. The alternative methods were extensively tested, and their performance was compared over several case study water distribution networks of vastly different sizes and complexities. The results showed that all of the new inverse methods are equally efficient and reliable, whereas the direct method is less reliable by having a higher frequency of failing to converge.

Optimal sampling locations to reduce uncertainty in contamination extent in water distribution systems.

Drinking water utilities rely on samples collected from the distribution system to provide assurance of water quality. If a water contamination incident is suspected, samples can be used to determine the source and extent of contamination. By determining the extent of contamination, the percentage of the population exposed to contamination, or areas of the system unaffected can be identified. Using water distribution system models for this purpose poses a challenge because significant uncertainty exists in the contamination scenarios (e.g., injection location, amount, duration, customer demands, contaminant characteristics). This article outlines an optimization framework to identify strategic sampling locations in water distribution systems. The framework seeks to identify the best sampling locations to quickly determine the extent of the contamination while considering uncertainty with respect to the contamination scenarios. The optimization formulations presented here solve for multiple optimal sampling locations simultaneously and efficiently, even for large systems with a large uncertainty space. These features are demonstrated in two case studies.

Calibration of the continuous water model based on the NRW patterns

Along with the urban development, water distribution systems have become increasingly important. Due to their complexity, integrated decision making has become more important. A major difference between simulated and observed data mostly initiates from the NRW which can be determined by conducting a district metered area study. Accordingly, current study was conducted to promote the calibration of the continuous model of water distribution system by the approach of the NRW pattern in accordance to water consumption pattern. Due to the lack of district metered area results, the difference in water production and all measured consumptions was considered as NRW. Three NRW patterns as various hypotheses were evaluated. Statistical Assessment revealed that application of an inline pattern of the subscriber consumption pattern as an NRW pattern provided a more reliable accurate calibration. The results confirmed that unauthorized and unregistered consumption had dominated the major amount of the NRW amount.

Dynamic Time Warping Clustering to Discover Socioeconomic Characteristics in Smart Water Meter Data

Socio-economic characteristics are influencing the temporal and spatial variability of water demand - the biggest source of uncertainties within water distribution system modeling. Improving our knowledge on these influences can be utilized to decrease demand uncertainties. This paper aims to link smart water meter data to socio-economic user characteristics by applying a novel clustering algorithm that uses dynamic time warping on daily demand patterns. The approach is tested on simulated and measured single family home datasets. We show that the novel algorithm performs better compared to commonly used clustering methods, both, in finding the right number of clusters as well as assigning patterns correctly. Additionally, the methodology can be used to identify outliers within clusters of demand patterns. Furthermore, this study investigates which socio-economic characteristics (e.g. employment status, number of residents) are prevalent within single clusters and, consequently, can be linked to the shape of the cluster's barycenters. In future, the proposed methods in combination with stochastic demand models can be used to fill data-gaps in hydraulic models.

Approach for Water Distribution System Model Calibration Based on Iterative Sherman–Morrison Formula

AbstractReal-time modeling of water distribution systems (WDSs) has received much attention in WDS operation and management. As the model input, nodal water demand must be calibrated in a timely ma...

Safety Is Easy

Health and safety are top of mind these days; in fact, one of my first columns of 2020 was titled “Health Is Hard.” But while the connections between human health and drinking water seem complex to me, safety seems pretty straightforward. The first step to not being injured is knowing that you can be injured. Accidents are usually preventable—just stay alert, and if you see something unsafe, do something about it immediately. Make sure your equipment is in good condition and safe to operate, and plan safety in advance and follow instructions. In addition to being alert to challenges from the COVID-19 pandemic, those in the water industry need to be careful when working in extreme temperatures and weather events, handling chemicals at the plant or in the lab, and crawling in confined spaces with power tools. Lockout/tagout, cutting, climbing, digging, driving, and for those on the front lines, the threats of workplace dangers are compounded by every public interaction. AWWA advocates that employers in the water industry fully adopt effective health, safety, and environmental programs developed according to established risk factors and regulatory compliance. Moving forward, it will be interesting to see risk and regulations change over the coming years in response to COVID-19, but to this end, AWWA provides a range of resources and is fully committed to supporting its members—and the entire water industry—as we navigate these trying times together. For example, because we all need to dress for safety on and off the job, AWWA's Let's Talk Safety comes with the timely chapter “PPE— A Workplace Fashion Statement.“ Manual M3, Safety Management for Utilities, can help when developing a health and safety program, and the committees working on the update are certainly working overtime to collect today's lessons learned for tomorrow's guidance. The Safety First videos provide how-to guidance for those who need hands-on training, and these can now be streamed online with a subscription. We all seek an injury-free work environment, but safety concerns that used to appear only during extreme tasks are now everyday occurrences. However, unlike the job we do in our professions, the job of getting through a pandemic doesn't pay anything. If fighting this virus costs us only good hygiene practices and the discomfort of wearing masks and face shields until the pandemic is behind us, it's not that expensive, and certainly cheaper than the alternative. If we work together, hopefully we can avoid expensive shutdowns and return our focus to keeping the water industry a safe place to work. This month's Journal AWWA features articles on water distribution system modeling, sizing meters and service lines, and water reuse, all topics that require having safety in mind. If you are interested in submitting an article, please contact me at journaleditor@awwa.org.

Water Distribution System Modeling: Past &amp; Present

Key TakeawaysModeling water distribution networks involves equations that are difficult to compute by hand, so early systems relied on simplifications and rules of thumb.Early computers were limiting but opened the door to quicker and less expensive calculations; modern computing has allowed more complex simulations.The future of water distribution system modeling may involve cloud‐based applications and integration of supervisory control and data acquisition, geographic information systems, and artificial intelligence.

Numerical investigation of the impact of irregular pipe wall build-up on velocity in the water distribution system

AbstractThis paper presents novel equations for different wall build-up types in old pipes developed for the estimation of real flow velocities in a water distribution system (WDS). This is important when estimating the contamination propagation rate in an operational WDS. Because the inner surface geometry of old rough pipes is complex, real velocities cannot be estimated by conventional WDS models. Therefore, a computational fluid dynamics (CFD) model was used to analyse the flow dynamics in old rough pipes with even and uneven roughness build-up. The developed equations for the velocity correction coefficients derive from the results of numerical simulations. Numerically obtained velocity fields show that in some cases, pipe wall build-up can affect the effective flow section significantly and the flow velocity can be underestimated by more than two times. Therefore, different velocity correction equations have to be used for different types of pipe wall build-up.

Streaming Smart Meter Data Integration to Enable Dynamic Demand Assignment for Real-Time Hydraulic Simulation

Water distribution system models have long been widely used for design and planning purposes. Their application for supporting real-time operational decisions has been also gaining increasing interest over the past decade. Accurate end-user nodal demands are critical to the reliability of hydraulic simulations for real-time decision support. Conventionally, nodal demands are set to a handful of periodically updated ensembles of demand patterns, which cannot represent the vast heterogeneity and volatility of demands. With advances in metering technology, consumption data with unprecedentedly high temporal and spatial resolutions are available to water utilities on a real-time basis. A framework is developed here to create a dynamic demand assignment hydraulic model, in which consumption data are assigned to nodes to update the water network model with the streaming data from the data center and without interruption of the hydraulic simulation run. The developed framework is cloud-based and scalable, making it suitable for water distribution systems of all sizes. The framework modifies the core EPANET engine to directly assign updated demands in order to overcome current software limitations. The model is applied and demonstrated using a real-world case study in the US. The results show the importance of the real-time demand assignment for the reliability of hydraulic models for making real-time operational decisions and the realization of digital twins of water infrastructure systems.