David Marlow

Linking climate projections to performance: A yield‐based decision scaling assessment of a large urban water resources system

Despite a decade of research into climate change impacts on water resources, the scientific community has delivered relatively few practical methodological developments for integrating uncertainty into water resources system design. This paper presents an application of the “decision scaling” methodology for assessing climate change impacts on water resources system performance and asks how such an approach might inform planning decisions. The decision scaling method reverses the conventional ethos of climate impact assessment by first establishing the climate conditions that would compel planners to intervene. Climate model projections are introduced at the end of the process to characterize climate risk in such a way that avoids the process of propagating those projections through hydrological models. Here we simulated 1000 multisite synthetic monthly streamflow traces in a model of the Melbourne bulk supply system to test the sensitivity of system performance to variations in streamflow statistics. An empirical relation was derived to convert decision-critical flow statistics to climatic units, against which 138 alternative climate projections were plotted and compared. We defined the decision threshold in terms of a system yield metric constrained by multiple performance criteria. Our approach allows for fast and simple incorporation of demand forecast uncertainty and demonstrates the reach of the decision scaling method through successful execution in a large and complex water resources system. Scope for wider application in urban water resources planning is discussed.

Application of metabolomics to understanding biofilms in water distribution systems: a pilot study.

Biofilms formed in pipes are known to contribute to waterborne diseases, accelerate corrosion and cause aesthetic taste and odour issues within the potable water supply network. This paper describes a pilot study, undertaken to assess the potential of using metabolomics to monitor bacterial activity in biofilms of an urban water network. Using samples from a water mains flushing programme, it was found that a profile of intracellular and extracellular metabolites associated with microbial activity could be obtained by analysing samples using gas chromatography mass spectrometry. Chemometric analysis of the chromatograms in conjunction with data from the mass spectrometer showed that it is possible to differentiate between biofilms from different pipe materials and planktonic bacteria. This research demonstrates that metabolomics has the potential for investigating biofilms and other microbial activity within water networks, and could provide a means for enhancing monitoring programmes, understanding the source of water quality complaints, and optimising water network management strategies.

A pathway to a more sustainable water sector: sustainability-based asset management

The water sectors of many countries are faced with the need to address simultaneously two overarching challenges; the need to undertake effective asset management coupled with the broader need to evolve business processes so as to embrace sustainability principles. Research has thus been undertaken into the role sustainability principles play in asset management. As part of this research, a series of 25 in-depth interviews were undertaken with water sector professionals from around Australia. Drawing on the results of these interviews, this paper outlines the conceptual relationship between asset management and sustainability along with a synthesis of the relevant opinions voiced in the interviews. The interviews indicated that the participating water authorities have made a strong commitment to sustainability, but there is a need to facilitate change processes to embed sustainability principles into business as usual practices. Interviewees also noted that asset management and sustainability are interlinked from a number of perspectives, especially in the way decision making is undertaken with respect to assets and service provision. The interviews also provided insights into the research needed to develop a holistic sustainability-based asset management framework.

Sewer Performance Reporting: Factors That Influence Blockages

Managing sewer blockages represents a significant operational challenge for water utilities. In Australia, company-level blockage rates are used to compare the effectiveness of the management strategies of different utilities. Anecdotal evidence suggests that this basis may not be a fair one for comparison because blockages are influenced by a range of factors beyond management control and vary from company to company. This issue was investigated as part of a broader research effort on sewer-blockage management undertaken in conjunction with the Water Services Association of Australia (WSAA) and its members. A Web-based survey was used to collate expert opinion on factors that influence blockage rate. The identified factors were then investigated in an exploratory analysis of blockage-related data provided by two participating utilities, supported by literature reviews. The results indicate that blockage rate is influenced by a range of factors, including asset attributes, climatic conditions, water consumption, and soil type. Because these factors vary from utility to utility, this research supports the finding that company-level blockage rate in itself is not an appropriate metric for comparing management effectiveness.

Prediction of Sewer Condition Grade Using Support Vector Machines

Assessing the condition of sewer networks is an important asset management approach. However, because of high inspection costs and limited budget, only a small proportion of sewer systems may be inspected. Tools are therefore required to help target inspection efforts and to extract maximum value from the condition data collected. Owing to the difficulty in modeling the complexities of sewer condition deterioration, there has been interest in the application of artificial intelligence-based techniques such as artificial neural networks to develop models that can infer an unknown structural condition based on data from sewers that have been inspected. To this end, this study investigates the use of support vector machine (SVM) models to predict the condition of sewers. The results of model testing showed that the SVM achieves good predictive performance. With access to a representative set of training data, the SVM modeling approach can therefore be used to allocate a condition grade to sewer assets with reasonable confidence and thus identify high risk sewer assets for subsequent inspection.

A framework for considering externalities in urban water asset management

Urban communities rely on a complex network of infrastructure assets to connect them to water resources. There is considerable capital investment required to maintain, upgrade and extend this infrastructure. As the remit of a water utility is broader than just financial considerations, infrastructure investment decisions must be made in light of environmental and societal issues. One way of facilitating this is to integrate consideration of externalities into decision making processes. This paper considers the concept of externalities from an asset management perspective. A case study is provided to show the practical implications to a water utility and asset managers. A framework for the inclusion of externalities in asset management decision making is also presented. The potential for application of the framework is highlighted through a brief consideration of its key elements.

Risk-based prioritization and its application to inspection of valves in the water sector

Isolation valves facilitate the effective operation and maintenance of water supply networks, but their sheer number presents a significant asset management challenge. If left unmanaged, valve reliability issues can become widespread. Inspections provide a means of increasing reliability, but a survey of industry practices indicated that some utilities did not have such a program in place. To improve asset management and reduce business risk exposure, such utilities need an effective means of commencing inspection programs. From a theoretical perspective, risk concepts provide a means of optimizing maintenance effort. However, in the face of poor data on reliability or condition, pragmatic approaches to risk-based prioritization are needed. One such approach, risk indexing, is considered in this paper. Background on the research is presented, including the application of risk-based inspection concepts within the water sector. The development of a risk indexing scheme is then investigated, drawing on two industry workshops in which the analytical hierarchy process was used to set relative weights. It is concluded that risk indexing provides the basis for a rational prioritization process in the absence of data on valve reliability or condition.

Sustainability-Based Asset Management in the Water Sector

Asset management should be a key vehicle for delivering sustainability goals of a business. However, for this to be the case, the link between sustainability outcomes and asset management inputs/outputs needs to be translated into terms that are meaningful to asset managers. In practice, however, asset managers often cannot see how their decisions link into sustainability objectives. Operationalising sustainability within asset management thus represents a significant challenge, even within the water sector where business activities are explicitly linked to ‘triple bottom line’ outcomes. To help meet this challenge, research has been undertaken into the role sustainability principles should play in asset management. As part of this research, a series of interviews have been undertaken with water sector professionals in Australia. The interviews aimed to collate opinion on the role sustainability concepts currently play in asset management, the role sustainability should play in the future, what the key barriers are, and where there is a need for research to help bridge the gaps. This paper outlines the conceptual relationship between asset management and sustainability principles, presents a synthesis of the results from these interviews, and indicates subsequent research efforts undertaken to help embed sustainability principles within the asset management business function.

Development of a Fuzzy Risk Ranking Model for Prioritizing Manhole Inspection

Manholes are designed to provide access points to underground sewer networks for inspection and maintenance. Manhole collapses, although rare, can result in severe consequences and have a significant effect on the performance of the sewer. This paper presents a case study on the development of a risk ranking model using fuzzy set theory and the analytical hierarchy process for individual manholes of sewer networks. The fuzzy risk ranking model (FRM) considered both the likelihood and consequence of collapse. The performance of the FRM was validated against 10 manholes with known poor condition. The results were also compared against a previously developed risk ranking scheme, with regards to consistency and repeatability of the relative ranking of assets. The results suggested that the FRM may provide better performance, although only limited data were available for validation. The process adopted in constructing the scheme is considered to be systematic and auditable.

Sewer Blockage Management: Australian Perspective

The functions performed by sanitary sewers can be disrupted by blockages in the pipeline, especially in cities with aging systems and deteriorating pipes. The problem is acute in Australia, where the principal blockage cause is tree root intrusion. This paper presents an overview of the causes of sewer blockages, the scope of the asset management challenge, and the management practices employed by Australian water utilities. These views were developed through reviews of the literature and current management practices elicited in a collaborative research project involving a range of water sector partners and using qualitative techniques such as surveys, interviews, and workshops. This paper highlights that blockages occur because of a range of factors, of which root blockages are the most common in Australia. Issues that confound management of blockages are also described, along with a summary of management strategies. Optimizing the balance between proactive and reactive interventions was found to be a go...