Evaluation methods for total water cycle management plans

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1 Fact Sheet January 2013 Evaluation methods for total water cycle management plans Total water cycle management (TWCM) is an important part of water policy in South East Queensland (SEQ). Research conducted by the Urban Water Security Research Alliance (the Alliance) evaluated the relevant impacts and trade-offs of different water, wastewater and stormwater management options to inform effective TWCM planning across SEQ. The SEQ Regional Plan provides the framework for managing the region s growth, land use and development. It requires water management to comply with the principles of TWCM and local governments in SEQ are now developing TWCM plans for the first time in Australia. TWCM calls for all elements of the water cycle, infrastructure, land use planning, and social, environmental and economic issues, to be considered in an integrated manner. The TWCM approach is necessary to sustainably, effectively and efficiently plan and manage an urban water and wastewater system. It ensures a sufficiently high quality and secure water supply for human use, while also protecting ecosystem health. The wide variety of water sources included in Australia s urban water plans and strategies present unique benefits, challenges and opportunities. Developing a portfolio of resources, that not only ensures water security and quality, but also balances financial, social and environmental costs and benefits, is a challenging task. Research outcomes Alliance research aimed to inform the rigorous and robust evaluation of alternative urban water management options for evidence-based TWCM in SEQ. Researchers developed a number of methods to improve the quantification of water quantity and quality, environmental and economic impacts, and the integrated assessment of these impacts. The outcomes of this research enables planners to make more informed estimates of the trade-offs between different water management options. To demonstrate their value in a living TWCM planning process, these methods have been applied in the evaluation of alternative water, wastewater and stormwater management scenarios for the Caboolture catchment, including the Caboolture Investigation Growth Area (CIGA) in the Moreton Bay Regional Council area. Evaluating the regional and catchment scale impacts of rainwater tanks Installation of rainwater tanks to supplement household water use is a common solution being considered as part of TWCM planning. The contribution of rainwater tanks to water supply security in the SEQ region and the impact they have on the reduction of nutrient and sediment discharges to Moreton Bay are the key criteria when comparing the performance of rainwater tanks against the performance of other solutions. The common method used to quantify total grid water savings from rainwater tanks at an urban scale is to simply multiply the outputs from the monitoring or modelling of individual tanks. Alliance researchers developed a new method to improve the accuracy and reliability of water saving estimates and overflows from rainwater tanks to enable more rigorous evaluation of this source option. Researchers quantified long-term expected grid water savings and reductions in runoff, total phosphorus (TP), total nitrogen (TN) and total suspended sediment (TSS) loads by considering the spatial variability of tank sizes, connected roof areas and household water use in the Sunshine Coast, Gold Coast, Brisbane, Ipswich and Moreton Bay local government areas. Leading water research and knowledge in South East Queensland

2 Variability of annual rainwater tank supply for 10,000 simulated houses based on the spatial variability present in Moreton Bay s tank and residential end use data (Simulation period: 1/01/1962 to 31/12/2011 Results show that the long-term expected yield from rainwater tanks vary from 35 kilolitres per household per year (kl/hh/year) in Ipswich to 50 kl/hh/year in the Sunshine Coast. The tank yields expected for Brisbane, Gold Coast and Moreton Bay, are 44 kl/hh/year. The long-term average tank yield expected for the SEQ region is 43 kl/hh/year. This method has been applied to the rainwater tank scenarios considered for the Caboolture catchment and CIGA, as part of the development of a TWCM plan for the Moreton Bay Regional Council. Ignoring the spatial variability of tank and residential water use characteristics in SEQ can overestimate the aggregated water savings from rainwater tanks by up to 15%, and underestimate the aggregated overflow from rainwater tanks by up to 10%. The results showed that ignoring the spatial variability of tank and residential water use characteristics in SEQ can overestimate the aggregated water savings from rainwater tanks by up to 15% and can underestimate the overflow from rainwater tanks by up to 10% in the Moreton Bay area. Underestimation of overflow from rainwater tanks can lead to an underestimation of nutrient and sediment loads discharging from residential catchments. This new method improves the accuracy and reliability of water saving estimates, and overflows from rainwater tanks (as well as the implications for nutrient and sediment loads), which will enable more rigorous evaluation of this source option. Evaluating water-related energy and greenhouse gas emissions Water-related energy use in cities is estimated to account for 13% of total electricity and 18% of the natural gas used by the average Australian. Collectively, this represents 9% of total Australian primary energy demands or 8% of total national greenhouse gas (GHG) emissions. Consequently, significant opportunities exist for reduction of GHG emissions by addressing the indirect influence of water management on energy use. Residential, industrial and commercial water-related energy use comprises 86% of water-related GHG emissions. Within homes, water-related energy use could account for approximately 35-50% of the GHG footprint of a relatively water conservative Queensland household (excluding transport emissions). Water-related energy use, eg, for heating and pumping, could account for approximately 35-50% of the GHG footprint within a Queensland home (excluding transport). Page 2

3 Water-related energy in homes includes water heating for showers, baths, taps, kettles, clothes and dish washing machines, hot water system losses, and energy for swimming pool and rainwater tank pumps and filters. A limited number of parameters account for a high proportion of the uncertainty surrounding water-related energy and associated GHG emissions in households. The water-energy nexus is explored in more detail in Fact Sheet 10 - The water-energy nexus. Understanding energy use associated with water use in homes and industry is vital to the TWCM planning, because a key objective in TWCM plans is to reduce the GHG footprint of water management options. Evaluating life cycle impacts Life Cycle Assessment (LCA) research is providing improved data and assumptions for use by TWCM planners in areas that have traditionally not been well understood. LCA includes additional environmental externalities, such as ozone depletion, mineral depletion and marine, freshwater and terrestrial ecotoxicity impacts. This provides a more rigorous, quantitative analysis across a broad spectrum of environmental and human health impacts to help guide decision making using a more comprehensive set of trade-offs. LCA was applied to three management scenarios for the Caboolture catchment that were developed as part of the TWCM planning study undertaken for the Moreton Bay Regional Council. Scenario 1 represents current business as usual, applying the minimum standard for urban stormwater treatment, and using rainwater tanks to meet the Queensland Development Code water savings targets. Scenario 2 incorporates additional measures, such as recycled water supplied to agricultural users, and more extensive catchment management measures. Scenario 3 adds in both retrofit and greenfield Water Sensitive Urban Design (WSUD) applications, plus urban non-potable reuse of Class A+ recycled water and stormwater. This was the most expensive option, but provides the greatest water savings and lowest overall nutrient discharge. Potable Water Savings (ML/y) Reduced Nitrogen Discharge (t/y) Default Data Excluded Greenhouse Gas Emissions (kt-c0 2 e/y) Excluded Using Improved Data Included (from avg grid mix) Included (from Scenario Scenario Scenario 3 2, The carbon footprint results for the three options were compared using the default data from the TWCMP study, using best-available datasets generated by the project team, and using different approaches to defining the system boundary for the analysis. This improved analysis increased the carbon footprint of the three options, particularly for the two more complex infrastructure configurations that involved wastewater recycling. The ranking of the options varied greatly, depending on the analytical approach used. Careful consideration of data quality and analytical scope used in the infrastructure selection process will help Water Utilities reduce their overall carbon footprint. LCA has shown that the incorporation of improved datasets and analytical methodology could change the ranking of water management scenarios in the TWCM planning process. Including different options for sewage collection and treatment in the LCA demonstrated the importance of the wastewater component to the overall environmental burden of urban water systems. Page 3

4 More detailed analysis of the Caboolture wastewater system then identified key data requirements, data gaps, benefits and constraints in applying LCA to wastewater systems. Life Cycle Assessment research provided improved data and assumptions for use by TWCM planners that would help guide decision making across a more comprehensive set of trade-offs. Evaluating externalities Based on a comprehensive literature review, Alliance researchers have compiled a compendium of externality effects and their monetary values for five different water supply options under consideration in SEQ - stormwater harvesting, rainwater tanks, centralised wastewater recycling, dams, and desalination. Page 4

5 An externality analysis was then applied to the three scenarios developed for the Moreton Bay Regional Council TWCM planning study to demonstrate the application on this method. The compendium provides water managers, scientists, and practitioners with a detailed reference to help incorporate the full range of costs and benefits into their option and scenario assessment and decision-making. It includes effects that are not usually taken into account directly in marketplace transactions, for example, CO ² emissions, habitat loss, improvement in river flow, commercial fishing, recreation, amenity and health. Improved information about the likely external or indirect effects of alternative water options and the magnitude of their economic impacts can assist in the efficient allocation of resources and avoid unexpected costs later in the project cycle. Extended cost effectiveness of water supply options Additional urban development results in increased pollutant loads. Different water servicing options have a different potential for reducing the amount of pollution that reaches the streams and bay. The Alliance research demonstrated the use of extended cost-effectiveness analysis to determine the least cost options for meeting sustainable pollutant load targets while supporting prudent and efficient investment in the water sector. Marginal Abatement Cost Curves for pollutants, such as total nitrogen (TN), total phosphorus (TP), total suspended solids (TSS) and GHG emissions, have been developed using data relevant to SEQ. The research has shown that by placing a price on pollution it is possible to extend cost-effectiveness to include environmental impacts in the evaluation of options for TWCM. The average abatement cost and benefit per tonne of pollutant to meet the no worsening load target over the 20 years were calculated for the Caboolture catchment. The weighted average cost of abatement was $334,000 per tonne, $40,000 per tonne and $213 per tonne for TP, TN and TSS respectively. The study showed that water supply options such as water recycling, stormwater harvesting and rainwater tanks reduce water pollution flows, and result in cost saving for abatement. However, the cost and performance of abatement options needs to be considered for each catchment. The cost of pollution depends upon the range of abatement options available in the catchment and the pollution reduction target. For example, abatement options could include point source or agricultural abatement of nutrients. Catchment characteristics such as slope can also affect cost and performance of abatement options. The pooling of outcomes from a number of TWCM plans may provide the most cost-effective approach to improving water quality in the region. Willingness-to-pay studies suggest that residents in one part of SEQ are willing to pay for improvement, whereas in other parts of SEQ only if it is more cost effective. This would require setting priorities for improvement across the region and may link with policies such as Water Quality Trading. However, this requires cooperation and coordination across Council areas and linking TWCM plans rather than consider them in isolation. Converting pollutant load reduction potential (tonnes) to mitigation costs using cost abatement curves enables the relative cost-effectiveness of alternative water servicing solutions to be estimated. Page 5

6 Integrated evaluation incorporating uncertainty and reliability Alliance researchers also investigated the development of a methodology to incorporate multiple, disparate evaluation criteria into a single decision-making framework in order to identify solutions that satisfy conflicting objectives. Researchers applied both multi-objective optimisation and Subjective Logic with Bayesian Networks incorporating uncertainty and reliability of information and data in an MCA framework to identify the most desirable strategic management option in the Caboolture catchment and CIGA. The method can be used as an alternative or extension to multi-criteria analysis (MCA). Without formally considering uncertainty, decisionmakers have no way of managing risks. Hence, the only risk management strategy is to avoid novel strategies. In the urban water sector, such risk aversion may lead to low uptake of promising, but potentially risky, new technologies. Alliance research results highlighted the applicability of these integrated assessment methods to the development of local government and sub-regional scale TWCM plans. Findings from this research are improving water managers ability to evaluate the uncertainty and impacts and trade-offs associated with the different urban water options being considered for inclusion in local and subregional TWCM Plans. Future research opportunities The various components that form the Alliance TWCM research project have been applied as a case study in the Moreton Bay Regional Council TWCM Plan, which will provide valuable insights and methods to improve TWCM planning across SEQ. However, further enhancement of evaluation methods is needed to bring these findings together to enable analysis of the multiple water source options under a variety of conditions and against a range of objectives. One such future research opportunity involves incorporating this Alliance research into a TWCM Planning Toolkit. This will allow different integrated water supply, wastewater and stormwater servicing options to be assessed in terms of their contribution to regional scale supply security, discharge implications to receiving waters, energy consumption, GHG emissions, economic costs and benefits and social acceptance. Application of such a TWCM Planning Toolkit to real case studies that test various water management and climate scenarios would demonstrate the value of the Toolkit and assist water managers to implement TWCM throughout SEQ, as well as in other states across Australia. Further information More detail on the above research can be found at www. urbanwateralliance.org.au Contact details Dr Shiroma Maheepala CSIRO Ph: Shiroma.maheepala@csiro.au Leading water research and knowledge in South East Queensland