Water Journal : Water Journal December 2012
sustainability refereed paper 84 DECEMBER 2012 water technical features Need for change Melbourne has just experienced a 13-year climatic sequence where the city’s water demand could not be met without imposing restrictions. Nitrogen discharging into Port Phillip Bay has had to be reduced by 1,000 tonnes per year, based on mid-1990 levels, and increasing greenhouse gas in the atmosphere could potentially reduce future catchment yield by as much as 35%. We have constraints, yet are still required to cater for a growing national population, which the Australian Bureau of Statistics (ABS) estimates will reach 33.6m, 44.7m, or 62.2m by 2010 (ABS, 2008), depending on three possible growth scenarios. It is the first time in history that half of the world’s population is living in cities, and this is forecast to increase to 80% by 2050 (UNEP, 2012). The challenge of servicing more people in a constrained environment is not unique to Australia or Melbourne alone, but is replicated in many cities around the world. Recognising that the major infrastructure designed and built today is actually shaping our cities of the future, it is important to consider how they contribute to addressing the needs of the future. Specifically considering that existing population numbers have reached the environmental limits in terms of water supply, greenhouse gas emissions and nutrient discharges in many cities, and population numbers could still increase by the order of 1.5 - to three-fold, we need to design all of our infrastructure to be in the order of 33% to 67% more efficient with regard to water use, greenhouse gas emission, and the nutrients discharged. This article has been specifically written to translate the concept of a ‘city of the future’ from an abstract concept into one where water utilities can clearly see the change that is required, and what they have to do. Examples of What Can be Done Faced with these environmental constraints and increasing population, Yarra Valley Water investigated what it would have to do to provide its services within these constraints, and accordingly deliver its services in a more environmentally sustainable way. It did this by first identifying that it had four different infrastructure challenges. These included: how it serviced greenfield sites, which make up 70% of development; how it serviced infill development, which make up the remaining 30% of development but could potentially increase up to 50% over time; how it serviced backlog areas, where it has about 17,000 properties that need to have their existing septic tank systems replaced; and ‘the elephant in the room’ – what to do with its existing developed areas. Examples demonstrating how each of these challenges were addressed follow: Greenfield sites: Kalkallo Yarra Valley Water will need to provide water and sewerage services to about 90,000 new homes in the northern growth corridor of Melbourne, spread over an area of about 16,300ha, within the next 30 years. This is located approximately 28km north of the Melbourne CBD. Hydraulically, this region is remote from both Melbourne’s existing water source and major sewage treatment plants. Both require four pump lifts to deliver the water and equally remove the sewage, which translated into energy requirements equates to 1,460 KWhr/ML, relatively high when compared to the average of Melbourne, which is in the order of 1,000 KWhr/ML. Recognising that this large growth corridor represented a unique opportunity to investigate whether a utility could provide its services in a more sustainable way, Yarra Valley Water engaged CSIRO and RMIT Centre for Design to help with the investigation. A range of alternative servicing options was considered, including a fully self-sufficient system on each property, a decentralised system with a local treatment plant, and a number of hybrids, with each compared to extending the existing centralised system. This early work in 2005 was formative in proving that it was theoretically possible to achieve improved environmental outcomes if an alternative servicing arrangement was chosen, rather than continuing with traditional method of just extending the existing infrastructure (Grant et al., 2006). So accordingly, when a 730ha land package came up for development in Kalkallo (Figure 1), the business embarked on a more detailed investigation. Key to that was working together with Hume City Council and Melbourne Water, the two key stakeholders in developing urban water services in the region. GHD was then engaged to undertake a feasibility study of this specific region. Options analysed included adding a 3.5KL or 10KL rainwater on each property, 40KL rainwater tanks shared among four joining properties, stormwater harvesting at the local and suburb scale, and conveying collected rainwater to Yan Yean Reservoir for subsequent treatment to drinking water standard some 21km away. F Pamminger Demonstrating the contribution a water utility can make CrEatiNG a City oF thE FuturE Figure 1. Kalkallo is an example of how a greenfield site can be serviced using 90% less reticulated water, discharge 45% less stormwater, discharge 25% less nutrients and use 75% less energy.
Water Journal February 2013
Water Journal November 2012-1