Kalanithy Vairavamoorthy

Methods and Tools for Managing Losses in Water Distribution Systems

AbstractThe 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...

Framework for Computing a Performance Index for Urban Infrastructure Systems Using a Fuzzy Set Approach

This paper presents a framework for characterizing, analyzing, and computing the performance of urban infrastructure systems. The framework is based on a systems approach and consists of performance indicators classified into three hierarchical levels: indicators, dimensions, and categories. A fuzzy synthetic evaluation technique has been developed to synthesize performance indicators into an index that ranges between 0 and 100. The performance of an individual infrastructure system, in the form of an index, is generated by aggregating the performance indicators in the first three hierarchical levels. The overall performance of the urban infrastructure systems is then obtained by combining the indexes of individual infrastructure systems. The relative importance of the performance indicators during the synthesis process is determined using the analytic hierarchy process technique. The framework demonstrates and measures the performance of the civil infrastructure systems in Kathmandu, Nepal. This framework can be applied to performance analysis of any infrastructure system in an urban area. It enables decision makers to identify the weak and strong components of urban infrastructure systems and to formulate appropriate strategies for infrastructure planning on the basis of performance and investment costs.

A New Approach of Decision Making Under Uncertainty for Selecting a Robust Strategy: A Case of Water Pipes Failure

Planning is a crucial part of delivering policies on sustainable development of urban infrastructure systems. However, strategic planning has been plagued due to future uncertainties. This paper presents a new technique based on information gap theory to analyze the failure rate of underground pipes under uncertainty and situations of scarce data. It predicts pipe failure based on a simple regression based model and Monte Carlo simulation technique. Once the failure rate is calculated, it analyses the robustness of failure using an information gap robustness function. The information gap robustness function ensures the robustness of the decision under maximum uncertainty without violating the minimum acceptable failure rate of the pipes. The methodology has been demonstrated on a case of water pipes failure in Birmingham UK. The trade-off between uncertainty and failure rate will be helpful for decision making while preparing a sustainable water pipes rehabilitation plan.

A Hybrid Approach of Uncertainty Analysis for Performance Measurement of Water Distribution System

Performance analysis of a water distribution systems involves hydraulic analysis to ensure that designed nodal demand in each node is maintained at a desired level of pressure and velocity over a design period. Those calculated performance values are mostly used as important surrogates while optimizing a systems design. However, input parameters used for the performance analysis are uncertain and both quantitative and semi-quantitative types. This paper presents a hybrid approach of uncertainty analysis to capture the both types of uncertainty associated in a water distribution systems. The uncertainty associated with nodal demands has been described by probability distribution functions and pipes roughness coefficient by fuzzy membership functions. The technique has been illustrated by a simple water distribution networks. The results from the hybrid approaches are consistent with the deterministic and stochastic approach.

Transitioning of urban water distribution systems.

The upgrade of urban water distribution systems (UWDS) amidst uncertain global change pressures is a challenging problem. To deal with this dilemma water utilities require approaches that enable UWDS to be transitioned at a minimal technical and socio-economic impact as uncertainties become known. A review of approaches for upgrading UWDS shows that existing cost models are skewed towards operation and maintenance costs without consideration for future transitionability. This thesis describes approaches for the sustainable transition of UWDS and their application on case studies. The thesis develops a conceptual framework for the analysis of UWDS transitions. It then develops a Socio-economic Impact Indicator (SII) framework based on Multi Criteria Decision Analysis and the Analytical Hierarchical Process to estimate impacts in an urban area due to UWDS transitions. It also develops an approach for modelling socio-technical transitions based on multinomial logistic regression. The thesis then develops an UWDS transition design approach that considers not only operation and maintenance costs (leakage and burst costs) but also transitionability and future socio-technical impacts costs. The developed approaches have been tested on case studies as proof of concept. Maximum cost saving can be realised when existing UWDS are upgraded with consideration of future UWDS transitionability.