Mark S. Morley

Battle of the Water Networks II

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

GAnet: genetic algorithm platform for pipe network optimisation

Abstract The marriage of object-oriented programming techniques and genetic algorithms (GAs) provides a uniquely flexible environment for the development of evolution programs with technical applications. Computerised representations of hydraulic network models are used in various guises throughout the water industry. As well as being commonly linked to relational databases to form asset management systems and to geographic information systems (GIS) to provide visualisation and mapping facilities, common applications include modelling the hydraulic performance of the network and use in network optimisation applications. This paper describes an architecture for an integrated optimisation application, GAnet, which comprises a GA application, a GIS and a hydraulic network solver.

Calibration of water distribution network models using genetic algorithms

Calibration of computer models for network analysis is a regular component of the model building process. Re-calibration of existing models is also necessary periodically, to reflect physical changes in the network. The process generally first involves a series of field tests during which pressures and flows are recorded at strategic locations in the system, usually continuously over one or more days. This is followed by a desk exercise during which adjustments are made to the rouglmess values used in modelling the system until a satisfactory match is obtained between modelled and observed values. If no satisfactory match is obtainable, further site checks are usually made to idehtify discrepancies between the model and the real system, such as incorrectly modelled valve settings and unrecorded connections. The selection of a satisfactory set of roughness values can be a tedious and time-consuming business when undertaken by the traditional trial and error approach. The authors show in this paper that the process can be largely automated using an optimisation approach that is well suited to the problem. The method adopted is a variation of the Genetic Algorithm, which is closely coupled with a network solver for maximum efficiency. Experience in using the automatic calibration software is presented using a case study from the UK.

A RAPID OPTIMIZATION PROTOTYPING TOOL FOR SPREADSHEET-BASED MODELS

This paper presents an application of a rapid prototyping tool utilising Single-Objective and MultipleObjective Genetic Algorithms (GA) to optimization problems defined using spreadsheets. The tool is implemented as an add-in for Microsoft Excel ® which combines a robust and powerful C++ library of GAs with a familiar user interface allowing for a fast and easy definition of objective functions. The tool can also be easily linked with various hydraulic solvers (e.g. EPANET) using VBA and thus presents a great instrument for researchers and practitioners who want to solve complex optimization problems (e.g. design, rehabilitation and calibration of water distribution systems) with a minimum of additional programming. The capabilities of the tool are demonstrated on the Hanoi Water Distribution System design problem as a multiple-objective optimization and the performance in terms of quality of obtained solutions is compared with those obtained with a single-objective formulation.

CONCEPTUAL RISK-BASED DECISION SUPPORT METHODOLOGY FOR IMPROVED NEAR REAL-TIME RESPONSE TO WDS FAILURES

This paper describes a conceptual risk-based decision support methodology for the operation of water distribution systems (WDS). More specifically, the methodology focuses on providing near real-time support to network operators to improve their response to failure conditions, such as pipe bursts, equipment failures, etc. The risk related to the impact of failures in WDS is used to guide, in near realtime, the operator’s approach and response to the failures. The impact metric of each failure is formed by a value tree comprising several basic impact factors affecting either the water utility or the customers. The impact assessment is undertaken by using a pressure-driven hydraulic model coupled with a Geographic Information System (GIS) considering explicitly the vulnerability of individual types of customers within the areas (potentially) affected by the failures under investigation. An intervention manager is also developed to assist the operator in testing the appropriateness of proposed interventions/responses to each failure. The intervention manager provides suggestions for improved courses of action determined through offline analyses of the system, stored in an interventions knowledge base in the form of ordered sets. The reduction of risk for each intervention is evaluated and compared to a “do nothing” alternative explicitly supporting risk-aware, near real-time decision making.

Hybrid Evolutionary Optimization/Heuristic Technique for Water System Expansion and Operation

AbstractThis paper presents a methodological solution to The Battle of Background Leakage Assessment for Water Networks (BBLAWN) competition. The methodology employs two constrained multiple-objective optimization problems and is implemented in the context of a software application for the generic hydraulic optimization and benchmarking of water distribution system (WDS) problems. The objectives are the combined infrastructure and operational costs and system-wide leakage, both to be minimized. In order to accelerate the evaluation of potential solutions, a distributed computing approach permits multiple EPANET solutions to be evaluated in parallel. A pressure-driven demand extension to EPANET assists the optimization in accurately ranking near-feasible solutions and to dynamically allocate leakage demand to nodes. Pressure-reducing valves (PRVs) have been located in two ways: a priori, with respect to the optimization analysis, and a posteriori after the infrastructure optimization to reduce excess press...

Continuous trait-based particle swarm optimisation (CTB-PSO)

In natural flocks, individuals are often of the same species, but there exists considerable variation in the traits possessed by each individual. In much the same way as humans display varied levels of aggression, gregariousness and inquisitiveness, so do the animals on which PSO is based [1]. Recent research has shown that this disparity of behaviour is very important in the ability of the flock to solve problems effectively, which might have profound implications for PSO. One of the key aspects is that although certain behaviour types (e.g. more adventurous individuals) might individually be better at problem solving; selecting for a group that all have adventurous traits has been shown to reduce the performance of the flock as a whole [1]. Therefore a flock that has a variety of behaviours leads to better performance in natural systems and it is this that motivates the work here. This paper explores a variant of PSO known as Continuous Trait-Based PSO (CTB-PSO) where individuals within a swarm have traits based on a continuous scale as opposed to discrete behaviour groupings.

A REAL-TIME INTERVENTION MANAGEMENT MODEL FOR REDUCING IMPACTS DUE TO PIPE ISOLATION IN WATER DISTRIBUTION SYSTEMS

This paper presents an Intervention Management Model (IMM), developed as part of a Decision Support System (DSS) for the real-time operational management of Water Distribution Systems (WDS). The IMM deals with the response to pipe bursts and leaks. It operates on the scenario where specific parts (pipes) of the WDS have been isolated by valve closures, to contain bursts and leaks. The IMM selects optimal interventions in order to minimise the impacts of this isolation for the customers. Options taken into consideration are: opening valves, modifying the outlet pressure from Pressure Reducing Valves (PRVs) and/or installing an overland bypass between fire hydrants. Impact estimation is carried out using hierarchical aggregation of partial impact indicators. A multiobjective algorithm is applied, with two objective functions: (a) minimising impacts to customers, and (b) minimising the number of interventions. Optimisation is carried out using a heuristic algorithm based on the Discrete Dynamic Dimensioned Search principles. The paper describes the structure, the methodology and the prototype implementation of the model within a DSS. The IMM presented in this paper forms only one component of a risk-based methodology for the operation of WDS under failure conditions, which has been developed as part of the EPSRC funded project NEPTUNE. The model is applied to a real-life case study in the Harrogate area of North Yorkshire, UK.