Water Journal : Water Journal September 2011
104 SEPTEMBER 2011 water water business water business NEED TO MODEL URBAN WATER USE? ASK BESS By Dr Mark Thyer, Senior Lecturer, School of Civil, Environmental and Mining Engineering, University of Adelaide, and Dr Matthew Hardy, Senior Environmental Engineer, BMT WBM Pty Ltd. As the Productivity Commission urges reform on a highly stressed urban water sector amidst growing pressure on water storages, Integrated Urban Water Management (IUWM) has never seemed more of an imperative. The "millennium" drought saw many urban water supply systems beset by historically low rainfall and inflows which forced unprecedented levels of water restrictions over recent years. Many Australian water authorities struggled to satisfy burgeoning demand. The IUWM design paradigm, with its accent on household and cluster scale water management solutions, is becoming widely embraced, because it provides a viable alternative to large- scale energy-intensive solutions for enhancing water supply security. IUWM imparts 'water sensitivity' to urban design while effectively integrating the physical and social sciences. It embraces a gamut of solutions, from awareness-raising to implementation of domestic water restrictions. Above all, it allows evaluation of the impact of demand management incentives -- adoption of water-efficient appliances, the installation of rainwater tanks and/or greywater reuse -- on the design and operation of urban water systems from the household (allotment), to the cluster (subdivision), to the regional (city-wide) scale. Understanding that urban water- cycle services meet at a range of scales, starting with a single allotment, is at the heart of IUWM. These meeting points facilitate examination of resource flows and allow for creation of internal loops and interactions to maximise resource efficiency and minimise system inputs and outputs. Traditionally, urban water service network models (incorporating potable supply, sewer and stormwater systems) have focused on a single spatial scale like a headworks, subdivision or allotment. While such a focus has naturally arisen from the constraints of computational complexity and the need to work within the boundaries of management authorities, the new paradigm needs tools capable of exploring linkages not only between scales, but also between water service systems. As water authorities and developers increasingly embrace the IUWM design paradigm, there is growing recognition that IUWM designs must be both effective and efficient. This means accepting that such traditional models of the urban water system will no longer be sufficient. Instead there is an urgent need for urban water service network models to incorporate a greater understanding of urban water flows at spatial and temporal scales significantly smaller than those traditionally adopted for such design work. These models require water use/ demand inputs that incorporate the dynamics of water use at shorter temporal and spatial scales. Yet while research on water use/ demand modelling has been going on since the 1960s, there are still very few models specifically for household water use at short temporal scales. Instead, most models developed at the individual household scale simulate total household demand at longer time scales, such as bi-monthly, quarterly or annual. These models have typically been either linear or non-linear regression-based. By contrast most models dealing with shorter temporal scales, e.g. hourly or daily, are developed at larger spatial scales, such as an entire city. Evaluating the impacts of IUWM systems requires the ability to capture variations in water use across a range of spatial and temporal scales. Since such IUWM design measures are often implemented at the household scale, knowledge of the dynamics of each water end use at the household scale at short time steps (sub-daily or daily) provide a valuable tool to assess the effectiveness of these incentives. Knowledge of the dynamics of household water use inevitably incorporates the human behavioural element. The Human Element By working to reduce reliance on mains water supplies and deliver better environmental outcomes, IUWM emphasises household- and cluster- scale water management solutions. It does so in part by allowing exploration of design scenarios which substitute tank water or greywater for household water uses such as toilet, shower, washing machine or outdoor use. Since these are typically implemented at the household scale, modellers need to understand the dynamics of each water end use. How many showers would the members of a given household or street have in any one week; how long would these showers last; and how much water would they typically consume? How many times would these householders flush the toilet in an hour or a day, and how much water would their washing machines and other water-using appliances consume? How does the water use change as people in the house or street adopt water-efficient appliances, or if architects, builders and developers installed more rainwater or greywater tanks and moved us away from the mains? These are the sorts of questions urban planners, managers and designers in the urban water sector grapple with every day. The Behavioural End-use Stochastic Simulator (BESS) (Thyer et al., 2011), developed by Thyer and colleagues in work funded by eWater CRC, takes a step towards filling the current gap by allowing users to simulate the way human behaviour impacts on household water use. It does so by stochastically simulating individual end uses at sub-daily time steps. WaterGEMS® and SewerGEMS HYDRAULIC ANALYSIS SOFTWARE TO HELP MAKE WATER SYSTEMS MORE EFFICIENT WaterGEMS and SewerGEMS come equipped with everything engineers need in a fexible multi-platform environment, from automated fre fow and water quality simulations, to criticality and energy cost analysis, to automated design, bottleneck detection, and water loss analysis. These applications are part of Bentley’s integrated water solution which addresses the needs of owner-operators and engineers who contribute to the infrastructure lifecycle. For more information, see the inside front cover of the September issue of Water Journal, visit www.bentley.com/AWA, or e-mail email@example.com.
Water Journal November 2011
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