Lydia S. Vamvakeridou-Lyroudia

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

AbstractWater 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...

Fuzzy hierarchical decision support system for water distribution network optimization

In this article, fuzzy hierarchical multi-objective optimization has been applied for the design of water distribution networks, using genetic algorithms (GAs). The problem has been formally structured as a multi-level multi-criteria decision making (MCDM) process with two objectives: cost minimization and benefits maximization, resulting in a Pareto trade-off curve of non-dominated solutions. A number of criteria are introduced and individually assessed by fuzzy reasoning. The overall benefits function is a combination (aggregation) of criteria, according to their relative importance and their individual fuzzy assessment. It is obtained through an analytic hierarchy process, applied directly within the GA, using an original mathematical approach. The decision maker enters data and preferences using exclusively linguistic ‘engineer friendly’ definitions and parameters. In this way, the whole design algorithm moves away from strict numerical functions and acts as a decision support system for the water network design optimization. The model has been applied to ‘Anytown’, a well-known benchmark network.

Parameterizing residential water demand pulse models through smart meter readings

This paper proposes a method for parameterizing the Poisson models for residential water demand pulse generation, which consider the dependence of pulse duration and intensity. The method can be applied to consumption data collected in households through smart metering technologies. It is based on numerically searching for the model parameter values associated with pulse frequencies, durations and intensities, which lead to preservation of the mean demand volume and of the cumulative trend of demand volumes, at various time aggregation scales at the same time. The method is applied to various case studies, by using two time aggregation scales for demand volumes, i.e. fine aggregation scale (1?min or 15?min) and coarse aggregation scale (1?day). The fine scale coincides with the time resolution for reading acquisition through smart metering whereas the coarse scale is obtained by aggregating the consumption values recorded at the fine scale.Results show that the parameterization method presented makes the Poisson model effective at reproducing the measured demand volumes aggregated at both time scales. Consistency of the pulses improves as the fine scale resolution increases. Poisson generation models with correlated pulse intensity and duration.Parameterization aimed at preserving mean and cumulative trend of demand volumes.Multiple time aggregation scales.Smart metering readings used in applications.The higher is the smart metering accuracy, the more consistent are the generated pulses.

Interdisciplinary assessment of sea-level rise and climate change impacts on the lower Nile delta, Egypt

CLImate-induced changes on WAter and SECurity (CLIWASEC) was a cluster of three complementary EC-FP7 projects assessing climate-change impacts throughout the Mediterranean on: hydrological cycles (CLIMB - CLimate-Induced changes on the hydrology of Mediterranean Basins); water security (WASSERMed - Water Availability and Security in Southern EuRope and the Mediterranean) and human security connected with possible hydro-climatic conflicts (CLICO - CLImate change hydro-COnflicts and human security). The Nile delta case study was common between the projects. CLIWASEC created an integrated forum for modelling and monitoring to understand potential impacts across sectors. This paper summarises key results from an integrated assessment of potential challenges to water-related security issues, focusing on expected sea-level rise impacts by the middle of the century. We use this common focus to illustrate the added value of project clustering. CLIWASEC pursued multidisciplinary research by adopting a single research objective: sea-level rise related water security threats, resulting in a more holistic view of problems and potential solutions. In fragmenting research, policy-makers can fail to understand how multiple issues can materialize from one driver. By combining efforts, an integrated assessment of water security threats in the lower Nile is formulated, offering policy-makers a clearer picture of inter-related issues to society and environment. The main issues identified by each project (land subsidence, saline intrusion - CLIMB; water supply overexploitation, land loss - WASSERMed; employment and housing security - CLICO), are in fact related. Water overexploitation is exacerbating land subsidence and saline intrusion, impacting on employment and placing additional pressure on remaining agricultural land and the underdeveloped housing market. All these have wider implications for regional development. This richer understanding could be critical in making better policy decisions when attempting to mitigate climate and social change impacts. The CLIWASEC clustering offers an encouraging path for the new European Commission Horizon 2020 programme to follow.

Application of Formal and Informal Bayesian Methods for Water Distribution Hydraulic Model Calibration

AbstractWater distribution system model parameter calibration is an important step to obtain a representative system model, such that it may be applied to understand system operational performance, often in real time. However, few approaches have attempted to quantify uncertainty in calibrated parameters, model predictions, and consider the sensitivity of model predictions to uncertain parameters. A probabilistic Bayesian approach is applied to calibrate and quantify uncertainty in the pipe roughness groups of an Epanet2 hydraulic model of a real-life water distribution network. Within the applied Bayesian framework, the relative performance of formal and informal Bayesian likelihoods in implicitly quantifying parameter and predictive uncertainty is considered. Both approaches quantify posterior parameter uncertainty with similar posterior distributions for parameter values (mean and standard deviation). However, the uncertainty intervals identified with the informal likelihood are too narrow, regardless ...

Research-supported participatory planning for water stress mitigation

With multi-stakeholder issues such as climate change or population growth providing significant challenges for water managers, participatory approaches to planning and management are becoming increasingly popular. To aid water stress mitigation in Bulgarias Iskar region, a participatory process with a broad range of stakeholders was designed and tested. Options adapted for the region such as risk management and industrial and domestic water conservation were studied. The results suggest that strong research support is needed to adapt participatory management theories into operational planning processes. Definition of appropriate working groups with clear roles and responsibilities are also needed to ensure effective implementation.

Comparative Analysis of System Dynamics and Object-Oriented Bayesian Networks Modelling for Water Systems Management

This paper presents a comparative analysis of System Dynamics Modelling (SDM) and Object-Oriented Bayesian Networks (OOBN). Both techniques are extensively used for water resources modelling due to their flexibility, effectiveness in assessing different management options, ease of operation and suitability for encouraging stakeholder involvement. Conversely, both approaches have several important differences that make them complementary. For example, while SDM is more suitable for simulating the feedback dynamics of processes, OOBN modelling is a powerful tool for modelling systems with uncertain inputs (or outputs) characterised by probability distributions. This comparative analysis is applied to the Kairouan aquifer system, Tunisia, where the aquifer plays an essential role for socio-economic development in the region. Both models produced comparable results using baseline data, and show their complementarity through a suite of scenario tests. It is shown that reducing pumping of groundwater to coastal cities may prove the key to reducing the current aquifer deficit, though local demand reduction must be considered to preserve the agricultural economy. It is suggested that water management assessment should be tackled using both approaches to complement each other, adding depth and insight, and giving a more coherent picture of the problem being addressed, allowing for robust policy decisions to be made.

Methods for Preserving Duration–Intensity Correlation on Synthetically Generated Water-Demand Pulses

AbstractThis paper proposes the application of three different methods for preserving the correlation between duration and intensity of synthetically generated water-demand pulses. The first two methods, that is, the Iman and Conover method and the Gaussian copula, respectively, are derived from known statistical approaches, although they had never been applied to the context of demand-pulse generation. The third is a novel methodology developed in this work and is a variation in the Gaussian copula approach. Poisson models fitted with the methods are applied to reproduce the measured pulses in one household, with parameters being obtained with the method of moments. Comparisons are made with another method previously proposed in the scientific literature, showing that the three methods have similar effectiveness and are applicable under more general conditions.

CALIBRATION OF WATER DISTRIBUTION SYSTEM USING TOPOLOGICAL ANALYSIS

This paper is part of the Battle of the Water Calibration Networks (BWCN) organized during the 12th annual Water Distribution Systems Analysis conference (WDSA 2010) in Tucson, Arizona. The BWCN calibration problem is formulated and solved as a multiobjective optimization problem with the objectives being the minimization of different types of absolute relative errors. The implicit constraints are comprised of mass and energy balance equations written for the extended period simulation model of the analyzed system and the five fire flow steady-state conditions. Calibration parameters are the grouped pipe roughness coefficients, two valve coefficients for one DMA, and a speed factor for one pump. Prior to calibration, the analysis of the pipe network topology has been performed. The hydraulic system results are spatially decomposed and simplified leading to substantial computational savings (without loss of accuracy) and enabling an easier analysis of results. The above calibration problem is solved using a multiobjective genetic algorithm. The results obtained on the BWCN case study demonstrate good agreement between the predicted and observed values.

Climate Change, Water Supply and Sanitation: Risk Assessment, Management, Mitigation and Reduction

Climate Change, Water Supply and Sanitation: Risk Assessment, Management, Mitigation and Reduction pulls together the final outcomes and recommendations from the PREPARED project that originated from the WSSTP (Water Supply and Sanitation Technology Platform) thematic working group Sustainable Water Management in Urban areas. The PREPARED project confirms and demonstrates the technological preparedness of water supply and sanitation systems of ten cities in Europe and also Melbourne and Seattle to adapt to the expected impacts of climate change. It shows that the water supply and sanitation systems of cities and their catchments can adapt and be resilient to the challenges of climate change; and that the technological, managerial and policy adaptation of these PREPARED cities can be cost effective, carbon efficient and exportable to other urban areas within Europe and the rest of the world. The book: ISBN: 9781780405001 (eBook) ISBN: 9781780404998 (Print)