Orbost Water Supply Demand Strategy
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East Gippsland Water 9 September 2010 Orbost Water Supply Demand Strategy Orbost Water Supply Demand Strategy AECOM Orbost Water Supply Demand Strategy Prepared for East Gippsland Water Prepared by AECOM Australia Pty Ltd Level 9, 8 Exhibition Street, Melbourne VIC 3000, Australia T +61 3 9653 1234 F +61 3 9654 7117 www.aecom.com ABN 20 093 846 925 9 September 2010 © AECOM Australia Pty Ltd 2010 The information contained in this document produced by AECOM Australia Pty Ltd is solely for the use of the Client identified on the cover sheet for the purpose for which it has been prepared and AECOM Australia Pty Ltd undertakes no duty to or accepts any responsibility to any third party who may rely upon this document. All rights reserved. No section or element of this document may be removed from this document, reproduced, electronically stored or transmitted in any form without the written permission of AECOM Australia Pty Ltd. 9 September 2010 Orbost Water Supply Demand Strategy AECOM Quality Information Document Orbost Water Supply Demand Strategy Ref 60144336 Task 1.06 Date 9 September 2010 Prepared by Marisa Cesario Reviewed by Steven Wallner Revision History Authorised Revision Revision Date Details Name/Position Signature A 31-May-2010 Draft for Client Comment Andrew Grant Original Signed Associate Director - Water B 09-Sept-2010 Final Issue for Publication Elisa Hunter 9 September 2010 Orbost Water Supply Demand Strategy AECOM Table of Contents Executive Summary i 1.0 Introduction 1 1.1 Regional Setting 1 1.1.1 Orbost 1 1.1.2 Marlo 1 1.1.3 Newmerella 1 1.1.4 Jarrahmond 1 1.1.5 Water Supply Catchment 2 2.0 Current Water Supply 3 2.1 Description of Water Supply System 3 2.1.1 Overview 3 2.1.2 Diversion 4 2.1.3 Storage 4 2.1.4 Water Treatment Plant 4 2.1.5 Supply 4 2.2 Allocation of Water 4 2.2.1 Bulk Water Entitlements 4 2.2.2 Licensed Diversions 5 2.2.3 Groundwater Licenses 5 2.3 Level of Service Objectives 5 2.4 Historical Water Restrictions 5 3.0 Previous Studies, Legislation and Regulation 7 3.1 Previous Long Term Planning Studies 7 3.1.1 Drought Response Plan for Bemm River, Buchan, Cann River, Marlo, Newmerella and Orbost (SKM, 2006) 7 3.1.2 EGW Water Supply and Demand Strategy (SKM, 2007) 7 3.2 Regulations and Legislation 7 3.2.1 Surface Water Caps 7 3.2.2 Streamflow Management Plans 7 3.2.3 Groundwater Caps 7 3.2.4 Regional River Health Strategy 8 3.2.5 Heritage Rivers 8 3.2.6 Victorian River Health Strategy 8 3.2.7 Legislation 9 4.0 Water Demand 10 4.1 Current Demand 10 4.1.1 Bulk Water Meter Data and Historical Diversions 10 4.1.2 Demand Profile Estimates 11 4.1.3 Customer Billing Data 12 4.1.4 High Volume Water Users 12 4.1.5 Unaccounted Water 12 4.1.6 Summary of Current Demand 13 4.2 Forecast Water Demand 13 4.2.1 Census Data 13 4.2.2 Victoria in the Future Data 14 4.2.3 East Gippsland Shire Council 14 4.2.4 Summary of Demand Projections 14 5.0 Demand Management 15 5.1.1 Current Demand Reduction Initiatives 15 5.1.2 Future Demand Reduction Initiatives 16 6.0 Water Supply 18 6.1 Risks and Uncertainties 18 6.1.1 Impact of Climate Change 18 6.1.2 Impact of Step Change 19 6.1.3 Impact of Bushfires 19 9 September 2010 Orbost Water Supply Demand Strategy AECOM 6.1.4 Forestry 20 7.0 Reliability of Supply 21 7.1 Current Reliability of Supply 21 7.2 Future Reliability of Supply 21 8.0 Management of Water Supply 23 8.1 Decommissioning the Rocky River Diversion 23 8.2 System Performance Improvements 23 8.2.1 Water Loss Reduction 23 8.3 Demand Management 23 8.4 Emergency Supply Options 24 8.4.1 Water Carting 24 8.4.2 Groundwater 24 8.5 Recycled Water 24 8.6 Recommendations for Managing Supply 25 9.0 Stakeholder Consultation 26 10.0 Conclusions and Recommendations 27 10.1 Conclusion 27 10.2 Summary of recommendations 27 11.0 References 28 9 September 2010 Orbost Water Supply Demand Strategy AECOM Executive Summary Water Supply Demand Strategies (WSDS) aim to ensure that an appropriate balance is maintained between urban water supply and demand over the long term planning horizon of 50 years. East Gippsland Water (EGW) finalised their WSDS for all water supply systems during 2007 and is now in the process of reviewing these strategies in light of updated climate change, growth and bushfire information. AECOM Australia Pty Ltd (AECOM) has been engaged by EGW to revise their existing WSDS for the Orbost water supply system. The Orbost water supply system services the towns of Orbost, Newmerella, Marlo and Jarrahmond. This revised WSDS will replace the strategy set out for the Orbost water supply system in EGW’s overall WSDS (Section 13). EGW has set level of service (LOS) objectives for water supply reliability. The objectives state that: Moderate restrictions (Stages 1 & 2) are not desired more frequently on average than 1 year in 10 More severe restrictions (Stages 3 & 4) are not desired more frequently than 1 year in 15. The LOS objectives have been used as a basis for assessing the adequacy of the Orbost water supply system for meeting current and future water demand. Recent studies and observations have shown that the impacts of climate change have already, and will most probably continue to result in significant reductions in streamflows. Streamflow within the Brobribb River alone has been reduced by approximately 48% over the last 12 years when compared to the historical long term average. Results from the assessments undertaken within this report and the previous WSDS (SKM, 2007) indicate that the Brodribb River (the major water source for the Orbost water supply system) is an extremely reliable supply source even with consideration of the most severe of climate change scenarios. Analysis of gauged data over the period 1947 to 2009 indicates that the minimum flow record on the Brodribb River was 17.8 ML/d during 2007. On this day EGW would have been able to extract their full entitlement of 5.74 ML/day. In addition, the predicted growth in water demand to 2055 (see Section 4.2) can easily be supplied with the existing bulk entitlement on the Brodribb River (see Figure 7). The existing diversion on the Rocky River could be decommissioned without any impact to reliability of supply although before doing so, consideration should be given to the other the benefits that the asset provides including its ability to operate as a low energy gravity supply in comparison to the pumped Brodribb River diversion. It was concluded that EGW will continue to be able to meet their LOS objectives for Orbost over the next 50 years even considering the significant impacts of climate change, past bushfires and growth in water demand. As a result, further supply enhancement will not be required. However it is recommended that EGW continue to optimise management of the Orbost water supply system by implementing the actions presented in Table E1. Table E1: Action Plan Action Implementation Investigate the variability in the volumes of unaccounted water reported Immediate Update the Orbost Drought Response Plan Immediate Continue to monitor the impacts of logging and if long term supply begins to Ongoing diminish, seek a reduction in the area to be logged within the water supply catchment Continue to implement demand reduction strategies Ongoing Undertake a water audit for the high water users 2011 Establish district metered areas to investigate the causes behind the variable 2011 levels of unaccounted water and if losses are found to be excessive (i.e. higher than 10%) continue to strive to reduce losses within the water supply system Investigate the costs associated with maintaining the Rocky River diversion to 2011 enable a cost-benefit analysis to be undertaken 9 September 2010 i Orbost Water Supply Demand Strategy AECOM 1.0 Introduction Water Supply Demand Strategies (WSDS) aim to ensure that an appropriate balance is maintained between urban water supply and demand over the long term planning horizon of 50 years. East Gippsland Water (EGW) finalised their WSDS for all water supply systems during 2007 and is now in the process of reviewing these strategies in light of updated climate change, population growth and bushfire information. Continuing dry conditions has resulted in a significant drop in streamflow right across Victoria and East Gippsland has not been exempt from these impacts. CSIRO has determined that climatic conditions are tracking above the previous high climate change scenarios, which suggests that the medium climate change scenario that was recommended by the Department of Sustainability and Environment (DSE) during preparation of the earlier WSDS may over estimate long term yields. The previous WSDS for the Orbost water supply system recommended that EGW: reduce uncertainty in the current and future water demand estimates; continue to pursue additional demand reduction options; replace ageing infrastructure and obtain legal certainty to entitlements through actions such as the transfer of existing bulk entitlements from the Rocky River to the Brodribb River and the decommissioning of the Rocky River diversion main. This document forms a revised WSDS for the Orbost water supply system and will replace the strategy set out for Orbost in EGW’s overall WSDS (Chapter 13) prepared by SKM in 2007.