Water Journal : Water Journal December 2012
refereed paper small water & wastewater systems water DECEMBER 2012 65 Baseline Analysis Outcomes Spatial planning enabled the mapping of metred water demand and floor space data, allowing for future growth in the LGA, with sub-catchment, catchment and citywide water balances developed to assist future decision-making. The results showed: • Existing potable water demand (by building and floor) to identify key water users by sector (e.g . multi-residential, single residential, food and beverage etc.) . Consumption results were then assessed against industry benchmarks to identify efficiency opportunities. • Future water demand forecasts (2030). • Non-potable demand at a building and floor level for 2030. • Potential volumes and locations of alternative source waters. • Synergies with other water systems and Green Infrastructure Strategies (e.g . trigeneration). • Issues and opportunities associated with climate change impacts including flooding, groundwater levels and sewage overflows. • The impact of demand density on stormwater and rainwater storage requirements and, therefore, volumetric reliability of those sources. The analysis provided a baseline rich with detailed information that could be overlayed and analysed simplistically to assist in identifying the opportunities of integrated water management beyond the baseline. Figure 6 summarises the spatial analysis approach in preparing the baseline. Opportunities Analysis Using the baseline data and water balance information, a rigorous process of matching supply with demand was commenced, incorporating network and pumping requirements (topography), indicative water balances and stormwater quality improvements to identify over 300 small-scale opportunities. These opportunities could theoretically be provided independently (at a lot or precinct scale) or together as part of a decentralised water network. The Recycled Water Plan focused on precinct scale and larger opportunities, assuming that lot scale solutions are available with or without a decentralised network. Stormwater harvesting opportunities incorporated into the decentralised water network included larger harvesting opportunities with potential to provide a water supply to a decentralised network. Refining the opportunities GHD, together with partner, The Institute of Sustainable Futures (ISF), developed a multi-criteria decision analysis (MCDA) process, including draft decision criteria, that was used to prioritise and consolidate the long list of opportunities from 300 to approximately 34 prioritised schemes. The preliminary decision criteria or “practical considerations” were designed to ensure that those schemes that performed well were more likely to be consistent with the city’s sustainability goals and feasible for potential investors. Examples of preliminary decision criteria adopted include: • System effectiveness: more water delivered per length of pipe and pumping required was preferred; • Pumping energy: lower energy was preferred based on topographical differences between supply source and demand location; • Uptake risk: the number of different properties included within a scheme compared to total demand; • Plumbing complexity: for example, schemes requiring retrofitting of ‘two- way’ pipe networks within existing buildings would be less likely to be undertaken; Figure 6. Spatial analysis summary.
Water Journal February 2013
Water Journal November 2012-1