TECHNICAL NOTE 2
ORANGE WATER RESOURCES
PREPARED FOR
ORANGE CITY COUNCIL
MAY 2013 TECHNICAL NOTE 2 ORANGE WATER RESOURCES
ORANGE CITY COUNCIL IWCM EVALUATION STUDY
PREPARED FOR: ORANGE CITY COUNCIL
MAY 2013
POSTAL ADDRESS PO BOX 1963 ORANGE NSW 2800 LOCATION 154 PEISLEY STREET ORANGE NSW 2800 TELEPHONE 02 6393 5000 FACSIMILE 02 6393 5050 EMAIL [email protected] WEB SITE WWW.GEOLYSE.COM TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Report Title: IWCM EVALUATION STUDY
Project: Orange City Council IWCM
Client: Orange City Council
Report Ref.: OCC_IWCM_Technical Note 2_Final.docx
Status: Final
Issued: May 2013
Next review: June 2018
Cover Photos:
Main – Suma Park Dam spillway (Source: OCC)
Top – Suma Park Reservoir (Source: Kerry Fragar)
Middle 1 – Stormwater harvesting batch pond (Source: Kerry Fragar)
Middle 2 – Orange STP Trickling Filter (Source: OCC)
Bottom – Harvested stormwater discharging to holding pond (Source: Martin Haege)
This report has been prepared by Geolyse Pty Ltd for Orange City Council and may only be used and relied on by Orange City Council for the purposes for which it was prepared. The preparation of this report has been in accordance with the project brief provided by the client and has relied upon the information, data and results provided or collected from the sources and under the conditions outlined in the report.
Geolyse otherwise disclaims responsibility to any person other than Orange City Council for liability howsoever arising from or in connection with this report. Geolyse also excludes implied warranties and conditions, to the extent legally possible.
The opinions, conclusions and recommendations in this report are based on conditions encountered and information reviewed at the date of preparing this report. Geolyse has no responsibility or obligation to update this report to account for events or changes occurring subsequent to the date that the report was prepared.
Geolyse reserves the right, at any time with or without notice, to amend, modify or retract any part or all of the report including any opinions, conclusions, or recommendations contained therein. Unauthorised use of this report in any form whatsoever is strictly prohibited.
OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
CONTENTS ABBREVIATIONS ...... VII INTRODUCTION ...... 1 1.1 BACKGROUND ...... 1 1.2 SCOPE OF TECHNICAL NOTE 2 ...... 2 1.3 LIMITATION OF TECHNICAL NOTE 2 ...... 2 1.4 REPORT STRUCTURE ...... 2 1.5 STUDY TEAM ...... 3 1.6 ACKNOWLEDGEMENT ...... 3
METHODOLOGY ...... 4 2.1 INTRODUCTION ...... 4 2.2 SECURE YIELD ...... 4 2.2.1 WHAT IS SECURE YIELD? ...... 4 2.2.2 BASELINE SECURE YIELD ...... 5 2.2.3 5/10/10 VS 5/10/20 ...... 6 2.2.4 APPROACH ...... 7 2.3 ORANGE WATER BALANCE MODEL ...... 7 2.3.1 DESCRIPTION ...... 7 2.4 CLIMATE CHANGE ...... 9 2.5 FINANCIAL ANALYSIS...... 10 2.5.1 NET PRESENT VALUE ...... 10 2.5.2 TYPICAL RESIDENTIAL BILL ...... 10 2.6 GREENHOUSE GAS ...... 10 2.7 COMPARISON OF OPTIONS ...... 11
WATER RESOURCES ...... 12 3.1 INTRODUCTION ...... 12 3.2 SURFACE WATER ...... 12 3.2.1 INTRODUCTION ...... 12 3.2.2 GOSLING CREEK DAM ...... 13 3.2.3 SPRING CREEK DAM ...... 16 3.2.4 SUMA PARK DAM ...... 18 3.2.5 LAKE CANOBOLAS ...... 26 3.2.6 MACQUARIE RIVER TO ORANGE PIPELINE ...... 29 3.2.7 BURRENDONG DAM TO ORANGE PIPELINE ...... 40 3.2.8 MULYAN CREEK DAM ...... 42 3.2.9 CADIA VALLEY OPERATIONS WATER INFRASTRUCTURE ...... 50 3.2.10 MANAGING STORAGE EVAPORATION ...... 50 3.2.11 LONG LIST RECOMMENDATIONS ...... 51 3.3 STORMWATER ...... 52 3.3.1 EXISTING STORMWATER HARVESTING SCHEMES ...... 52 3.3.2 BLACKMANS SWAMP CREEK 100% TRIGGER ...... 63 3.3.3 BLACKMANS SWAMP CREEK STAGE 2 ...... 65 3.3.4 BLACKMANS SWAMP CREEK STAGE 3 ...... 69 3.3.5 BLACKMANS SWAMP CREEK MAXIMUM HARVESTING ...... 72 3.3.6 DOWNSTREAM STORMWATER HARVESTING ISSUES ...... 75 3.3.7 UPSTREAM STORMWATER HARVESTING ...... 75 3.3.8 NORTHERN SUBURBS STORMWATER HARVESTING (BEER ROAD) ...... 79 3.3.9 LONG LIST RECOMMENDATIONS ...... 81 3.4 RAINWATER TANKS ...... 81
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3.4.1 INTRODUCTION ...... 81 3.4.2 RAINWATER TANK REBATE POLICY...... 82 3.4.3 ASSESSMENT OF RAINWATER TANKS ...... 82 3.4.4 RESULTS ...... 85 3.4.5 USE OF RAINWATER TANKS AS A WATER SUPPLY OPTION ...... 88 3.4.6 SUMMARY ...... 89 3.4.7 LONG LIST RECOMMENDATION ...... 89 3.5 GROUNDWATER ...... 89 3.5.1 SPRING HILL AND LUCKNOW ...... 89 3.5.2 EXISTING GROUNDWATER RESOURCES FOR ORANGE ...... 90 3.5.3 POTENTIAL GROUNDWATER RESOURCES ...... 91 3.5.4 LONG LIST RECOMMENDATIONS ...... 95 3.6 TREATED EFFLUENT...... 95 3.6.1 DESCRIPTION ...... 95 3.6.2 VOLUME ...... 95 3.6.3 INDIRECT POTABLE REUSE ...... 99 3.6.4 LONG LIST RECOMMENDATIONS ...... 108 3.7 REGIONAL WATER RESOURCES ...... 108 3.7.1 CENTROC STUDY...... 108 3.7.2 LAKE ROWLANDS...... 109 3.7.3 MOLONG CREEK DAM ...... 112 3.7.4 LONG LIST RECOMMENDATIONS ...... 112 3.8 OTHER ...... 112 3.8.1 LUCKNOW MINE – REFORM SHAFT...... 112 3.8.2 BROWNS CREEK MINE ...... 113 3.8.3 WATER CARTING ...... 117 3.8.4 LONG LIST RECOMMENDATIONS ...... 119 3.9 DEMAND MANAGEMENT ...... 119 3.9.1 INTRODUCTION ...... 119 3.9.2 RESTRICTION FREQUENCY AND DURATION ...... 120 3.9.3 CONSERVATION WATER PRICING ...... 121 3.9.4 LONG LIST RECOMMENDATIONS ...... 122
ASSESSMENT OF OPTIONS ...... 123 4.1 INTRODUCTION ...... 123 4.2 WATER SECURITY ...... 123 4.2.1 COMPARING SECURE YIELD WITH DEMAND ...... 123 4.2.2 SENSITIVITY OF PROJECTIONS ...... 125 4.3 BUSINESS AS USUAL WATER SECURITY...... 127 4.4 FUTURE WATER SUPPLY OPTIONS ...... 130 4.4.1 UPDATE SINCE PRG MEETING 3 ...... 130 4.4.2 LONG LIST OF OPTIONS ...... 131 4.4.3 SHORT LIST OPTIONS ...... 134 4.4.4 EVALUATION OF SHORT LISTED OPTIONS ...... 135
CONCLUSIONS AND RECOMMENDATIONS ...... 138 5.1 CONCLUSIONS ...... 138 5.2 RECOMMENDATIONS...... 138
REFERENCES ...... 139 APPENDICES
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APPENDIX A Quote for Rainwater Tank Installation
APPENDIX B IBL Solutions Reports
APPENDIX C Climate Change Modelling Results
APPENDIX D QBL Results
TABLES Table 1.1 – Study team ...... 3 Table 2.1 – Comparison of secure yield rules ...... 6 Table 3.1 – Supply from external sources for assessment of raising Suma Park Dam ...... 22 Table 3.2 – Secure yield results for raising Suma Park Dam ...... 23 Table 3.3 – Summary of Option SW1: raise Suma Park Dam by 1.0 m ...... 26 Table 3.4 – Lake Canobolas scheme performance ...... 28 Table 3.5 – Summary of Option SW2: Lake Canobolas ...... 29 Table 3.6 – Comparison of actual and modelled annual water consumption – 2000 to 2010 analysis 37 Table 3.7 – River flow and extraction – 2000 to 2010 analysis ...... 38 Table 3.8 – Macquarie pipeline average annual operating costs ...... 38 Table 3.9 – Summary of Option SW3: Macquarie River to Orange pipeline ...... 39 Table 3.10 – Burrendong Dam pipeline – preliminary cost estimates ...... 41 Table 3.11 – Summary of Option SW4: Burrendong Dam to Orange pipeline ...... 42 Table 3.12 – Conceptual Mulyan Creek Dam Stage-Storage-Surface Area Data ...... 46 Table 3.13 – Mulyan Creek Dam – preliminary cost estimates ...... 49 Table 3.14 – Summary of Option SW5: Mulyan Creek Dam ...... 49 Table 3.15 – Average storage evaporation loss ...... 50 Table 3.16 – BSCSHS Operating Rules ...... 57 Table 3.17 – BSCSHS Staging ...... 58 Table 3.18 – PCSHS Operating Rules ...... 59 Table 3.19 – Summary of harvest volumes from approved stormwater harvesting schemes ...... 62 Table 3.20 – Summary of harvest volumes from stormwater harvesting schemes on 100% trigger .... 63 Table 3.21 – Summary of Option SH0: BSCSHS Stage 1b ...... 65 Table 3.22 – Summary of harvest volumes from BSCSHS Stage 2 ...... 67 Table 3.23 – BSCSHS Stage 2 – preliminary cost estimates ...... 68 Table 3.24 – Summary of Option SH1: BSCSHS Stage 2 ...... 68 Table 3.25 – Summary of harvest volumes from BSCSHS Stage 3 ...... 70 Table 3.26 – BSCSHS Stage 3 – preliminary cost estimates ...... 71 Table 3.27 – Summary of Option SH2: BSCSHS Stage 3 ...... 72 Table 3.28 – Summary of harvest volumes from maximum BSCSHS ...... 73 Table 3.29 – Maximum BSCSHS – preliminary cost estimates ...... 74 Table 3.30 – Summary of Option SH3: Maximum BSCSHS ...... 74 Table 3.31 – Upstream harvesting results ...... 77 Table 3.32 – Upstream stormwater harvesting – preliminary cost estimates ...... 78 Table 3.33 – Summary of Option SH4: Upstream stormwater harvesting ...... 78 Table 3.34 – Upstream stormwater harvesting – preliminary cost estimates ...... 80 Table 3.35 – Summary of Option SH5: Upstream stormwater harvesting (Beer Road) ...... 80 Table 3.36 – Tank Rebate Policy ST061 – rebate schedule ...... 82 Table 3.37 – Household water demand profile used for rainwater tank modelling ...... 82 Table 3.38 – Assumptions and Input to the rainwater tank model ...... 83 Table 3.39 – Tank and installation costs – Scenario 1 ...... 84 Table 3.40 – Tank and installation costs – Scenarios 2 and 3 ...... 84 Table 3.41 – Summary of rainwater tank financial analysis ...... 87 Table 3.42 – Summary of Option RW1: Rainwater tanks ...... 89 Table 3.43 – Orange town water supply bores ...... 90 Table 3.44 – Summary of Option GW1: Bores ...... 91 Table 3.45 – Annual effluent transfer to CVO ...... 98
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Table 3.46 – Spring Hill and Lucknow effluent production forecast ...... 99 Table 3.47 – Summary of Option E1: Non-membrane IPR scheme ...... 101 Table 3.48 – Summary of Option E2: Membrane IPR scheme ...... 102 Table 3.49 – Orange STP storm flow storage ...... 105 Table 3.50 – STP storm flow capture – preliminary cost estimates ...... 106 Table 3.51 – Summary of Option E5: STP storm flow recovery scheme ...... 107 Table 3.52 – Summary of Option R1: Pipeline from augmented Lake Rowlands ...... 111 Table 3.53 – Estimated capital costs for Browns Creek mine to Orange water transfer system ...... 116 Table 3.54 – Summary of Option O2: Browns Creek mine water transfer ...... 116 Table 3.55 – Water cartage options ...... 118 Table 3.56 – Water cartage summary of capital and operating costs ...... 119 Table 3.57 – Orange forecast water demand – BAU ...... 122 Table 3.58 – Orange forecast water demand – high level demand management ...... 122 Table 4.1 – Existing water system secure yield ...... 124 Table 4.2 – Water supply management strategy infrastructure options...... 127 Table 4.3 – Long list options ...... 131 Table 4.4 – Short-listed water security options ...... 135
FIGURES Figure 1: Water balance model schematic ...... 8 Figure 2: Surface water catchments ...... 14 Figure 3: Gosling Creek Reservoir stage-storage curve ...... 15 Figure 4: Spring Creek Reservoir stage-storage curve...... 17 Figure 5: Suma Park Reservoir stage-storage curve ...... 19 Figure 6: Suma Park Dam storage-yield curve ...... 25 Figure 7: Modelled additional Suma Park Dam storage during critical drought period ...... 25 Figure 8: Lake Canobolas connection options ...... 27 Figure 9: Proposed Macquarie River pipeline ...... 31 Figure 10: Macquarie River catchments ...... 32 Figure 11: Modelled Macquarie River flow duration curve (Geolyse, 2012) ...... 34 Figure 12: FDC impact for 12/34 rule ...... 35 Figure 13: Monthly Macquarie River flow data (Scenario B) – January 2000 to December 2010 ..... 36 Figure 14: Combined storage behaviour: 2000 to 2010 analysis ...... 37 Figure 15: Conceptual pipeline route from Burrendong Dam to Orange ...... 41 Figure 16: Conceptual Mulyan Creek Dam, catchment ...... 44 Figure 17: Mulyan Creek mass curve of inflow to proposed dam ...... 45 Figure 18: Mulyan Creek Dam storage-demand relationship ...... 45 Figure 19: Conceptual Mulyan Creek Dam ...... 46 Figure 20: Potential annual demand supplied by 1,350 ML Mulyan Creek Dam ...... 47 Figure 21: Conceptual demand supplied through Federation Drought period for Mulyan Creek Dam...... 47 Figure 22: Preliminary hydraulic grade line and pipe sizes ...... 48 Figure 23: Stormwater harvesting infrastructure ...... 52 Figure 24: Stormwater harvesting catchments ...... 55 Figure 25: BSCSHS Stage 1 scheme layout ...... 56 Figure 26: NSW Office of Water approval framework – Water quality ...... 61 Figure 27: BSCSHS Stage 1 flow duration curves ...... 64 Figure 28: BSCSHS Stage 2 conceptual offline wetland system ...... 66 Figure 29: BSCSHS Stage 2 flow duration curves ...... 67 Figure 30: BSCSHS Stage 3 conceptual harvesting weir ...... 69 Figure 31: BSCSHS Stage 3 flow duration curves ...... 71 Figure 32: Maximum BSCSHS flow duration curves ...... 73 Figure 33: Upstream stormwater harvesting locations...... 76 Figure 34: Potential northern suburbs stormwater harvesting (Beer Road) ...... 79 Figure 35: Rainwater Tank Analysis – Potential Household Water Saving ...... 85 Figure 36: Scenario 1 – Rainwater tank size comparison for outside use only ...... 86 Figure 37: Scenario 2 – Rainwater tank size comparison for outside and toilet use ...... 86 Figure 38: Scenario 3 – Rainwater Tank Size Comparison for Outside, Toilet Use and Washing Machine ...... 87 Figure 39: Orange water supply bores ...... 90
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Figure 40: Forecast total annual effluent production – city of Orange, medium growth ...... 96 Figure 41: Forecast total annual effluent production – city of Orange, high growth ...... 96 Figure 42: BAU treated effluent production and availability ...... 98 Figure 43: IPR non-membrane treatment train ...... 100 Figure 44: IPR membrane treatment train ...... 102 Figure 45: Average household water use, kL/year ...... 108 Figure 46: Potential pipeline from Lake Rowlands to Orange ...... 110 Figure 47: Browns Creek mine to Orange pipeline route options ...... 115 Figure 48: Water security for existing water supply infrastructure – no climate change ...... 125 Figure 49: Water security for existing water supply infrastructure – with climate change ...... 126 Figure 50: Water security with BAU water supply infrastructure – no climate change ...... 129 Figure 51: Water security with BAU water supply infrastructure – with climate change ...... 130
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Orange City Council’s Integrated Water Cycle Management
Integrated Water Cycle Management (IWCM) is a 30 year strategic planning tool that enables Orange City Council to manage urban water services in a holistic manner and in accordance with best management practice. It brings together water supply, sewerage and stormwater within a catchment context, identifies current and potential future issues relating to planning and service delivery and examines how these issues can best be addressed.
IWCM Evaluation Study
The IWCM Evaluation Study lists all urban water service targets and identifies all the issues relating to planning and service delivery for urban water supply, sewerage and stormwater over the next 30 years. It examines what issues: • can be addressed by existing or formally adopted actions and capital works – the Business as Usual scenario; or • remain to be addressed in the IWCM Strategy.
Technical Notes
The IWCM Evaluation Study is supported by a number of Technical Notes that provide detailed supporting information and analysis. Findings from the technical work are presented in the relevant sections of the IWCM Evaluation Study.
Technical Note 1: IWCM Targets and Community Objectives
This Technical Note details the relevant targets and community objectives for the delivery of urban water services for Orange City Council.
Technical Note 2: Orange Water Resources
This Technical Note presents details of the various water resources considered by Orange City Council to provide long term water security including: surface water, stormwater, rainwater, groundwater, treated effluent, regional supplies and other solutions. It defines secure yield and how it relates to long term water security. It also includes an analysis of how climate change may impact on the secure yield.
Technical Note 3: Potable Water Demand and Effluent Production
This Technical Note describes the assessment of future potable water needs and effluent production for Orange and the villages of Lucknow and Spring Hill. Demand projections are based on consideration of historical demand, demand drivers and demand management.
Technical Note 4: Typical Residential Bill Analysis
This Technical Note defines what the Typical Residential Bill (TRB) is and details the modelling undertaken to determine the TRB and the impact of current and proposed actions and capital works.
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ABBREVIATIONS ABS Australian Bureau of Statistics
BAU Business as usual CVO Cadia Valley Operations D/S Downstream
DEUS Department of Energy, Utilities and Sustainability DoP Department of Planning DPWS Department of Public Works and Services
EA Emergency Authorisation issued under Section 22A of the Water Act 1912 ERP Estimated Residential Population GPT Gross Pollutant Trap
GL Gigalitre (1,000 megalitres) ha Hectares IPR Indirect potable reuse IWCM Integrated Water Cycle Management kL Kilolitre (1,000 litres) kWhr Kilowatt hour L Litre (1,000 millilitres) LGA Local Government Area L/s Litres per second LEP Local Environmental Plan mg/L Milligrams per litre m3/hr Cubic metres per hour mL Millilitre ML Megalitre (1 million litres or 1,000 kilolitres) ML/day Megalitres per day m Metre mm Millimetres NOW NSW Office of Water NPV Net Present Value OCC Orange City Council pa Per annum QBL Quadruple bottom line (environmental, social, economic and governance)
REF Review of Environmental Factors STP Sewage Treatment Plant (works) TBL Triple bottom line (environmental, social and economic)
TRB Typical Residential Bill µg/L Micrograms per litre U/S Upstream UV Ultraviolet WTP Water Treatment Plant (works) WWTP Wastewater Treatment Plant (or STP)
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Introduction
1.1 BACKGROUND
A hydrology study completed in 1990 determined that the secure yield for the Orange surface water system, including the storages of Suma Park, Spring Creek and Gosling Creek Reservoirs was 7,800 ML/year (Public Works, 1990). This formed the basis of the volumetric water entitlement issued under the Water Management Act, 2000 for the Orange water supply.
The city’s annual water demand reached 7,120 ML in 2002. Since that time, Orange City Council has introduced substantial demand management and efficiency measures that have reduced annual water consumption. Despite this, the experience during the 2000 to 2010 drought period indicated that Orange’s water supply was not as secure as indicated by the 1990 study.
The Integrated Water Cycle Management (IWCM) Concept Study (MWH, 2007) identified that the system secure yield needed to be updated. NSW Water Solutions was engaged by Orange City Council to undertake this review.
The initial results of the secure yield review became available to Council in February 2008 and showed a dramatic reduction in the secure yield from the 1990 figure of 7,800 ML/year to 3,500 ML/year1.
The 2008 secure yield review used an extended climate data set that covered the period 1890 to 2007. The dramatic reduction in the calculated secure yield was put down to the influence of the Federation Drought (1895 to 1902), which was the critical drought period in the analysis, and improved streamflow modelling2. It was also considered at the time that the lower secure yield was being reflected in the current situation where the extended drought period from 2000 was putting pressure on the city’s water resources. It was evident that the city’s secure yield was less than the current and estimated future water demand.
Council has made some significant ground with demand management. The current unrestricted annual water demand with these measures in place is 5,400 ML/year (refer to Technical Note 3) and it is forecast that demand will remain at or around this level for the next 10 years despite continued forecast population growth. This indicates Council is expecting the community to become more water efficient.
Orange City Council adopted a comprehensive Strategic Water Supply Strategy at its meeting of 19 November 2009. The strategic objective of the strategy is:
To establish a broad based water supply strategy for the next 50 years and beyond which focuses on ongoing water conservation, quality and demand management and the provision of key water supply infrastructure at least 10 years in advance of projected demand.
The ultimate aim of the strategy is to see fewer restrictions, improved security, and capacity for ongoing growth.
In 2007, Orange City Council commenced investigation of a range of alternative water supply sources that lead to the development of stormwater harvesting on Blackmans Swamp Creek. The 2009 strategy continued on from this work and included a range of local and regional water supply infrastructure options that would be considered as part of a future water supply system.
This Technical Note presents a comprehensive review of water resources in and around Orange that have been considered for future water supply augmentation.
1 This initial study result has since been updated. The revised secure yield for the existing catchment and storages based on the 5/10/10 rule is 3,400 ML/year. 2 The dramatic reduction in secure yield has since been confirmed through numerous analyses and revisions undertaken throughout the IWCM Evaluation Study.
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This review applies to the Orange water supply only. The villages of Spring Hill and Lucknow are supplied from groundwater sources and modelling of this system (as presented in Technical Note 3) indicates adequate supplies for the next 50 years.
1.2 SCOPE OF TECHNICAL NOTE 2
This Technical Note presents details of the various water sources considered by Orange City Council to provide long term water security including: surface water, stormwater, rainwater, groundwater, treated effluent, regional supplies, other emergency solutions and demand management.
For each viable water source option, the Technical Note provides an assessment of: • how it would work; • the potential increase in secure yield; • the effectiveness of the option; • capital and annual operating cost and Net Present Value (NPV); • how the option would impact on the Typical Residential Bill (TRB); • potential operational greenhouse gas emissions; and • approvals and licencing requirements, possible issues and likely approvals timeframes.
Six water supply infrastructure components are currently included in Council’s Business as Usual (BAU) scenario. These were adopted by Council in its 2009 Strategic Water Supply Strategy. The ability of these components to provide water security for the next 50 years is assessed with and without climate change.
1.3 LIMITATION OF TECHNICAL NOTE 2
This report presents a preliminary evaluation of technically feasible options to increase the city’s secure yield. It is a broad, high level strategic evaluation and seeks to identify those options that could be considered as part of Council’s water supply system. The options short-listed from this assessment would be subject to further detailed analysis, environmental assessment and legislative approvals/licencing. As such, the numbers presented in this report are subject to change and should not be taken as final. For example, the assessment of how much a certain option may be able to provide in terms of average annual supply or secure yield may change during the detailed environmental approvals stage due to some yet to be identified environmental constraint.
1.4 REPORT STRUCTURE
This report is structured as follows: • Section 2 provides an outline of the methodology used to assess various water supply options. This section includes a description of secure yield and climate change modelling and defines the metrics used to compare water supply options; • Section 3 provides a description of the water supply options considered throughout preparation of the IWCM Evaluation Study including costs and potential to improve the city’s secure yield; • Section 4 provides an assessment of the BAU water supply components and short lists other viable options for future consideration; and • Section 5 provides the conclusions and recommendations.
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1.5 STUDY TEAM
Table 1.1 outlines the study team and their respective roles.
Table 1.1 – Study team
Organisation Role
Geolyse Pty Ltd • Project management • Background data collation • Analysis of data • Assessment and modelling of options • Financial modelling • Coordination of secure yield modelling • Assessment and reporting
NSW Water Solutions • Secure yield modelling • Climate Change modelling
1.6 ACKNOWLEDGEMENT
The secure yield modelling undertaken for options considered in this assessment was undertaken by NSW Water Solutions (Mr Peter Cloke and Mr Chee Chen).
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Methodology
2.1 INTRODUCTION
This section provides an outline of the methodology used to assess various water supply options. A range of metrics were used to allow comparison of viable water source options. These included: • the potential increase in secure yield; • capital and annual operating costs and Net Present Value (NPV); • how the option would impact on the Typical Residential Bill (TRB); and • potential operational greenhouse gas emissions.
Climate change assessment was undertaken for the water supply components of the Business as Usual (BAU) scenario.
The methodology used to derive each metric is provided in the following sections.
2.2 SECURE YIELD
2.2.1 WHAT IS SECURE YIELD?
Orange City Council is using secure yield as a quantitative measure for comparing various water supply options. The secure yield assessments are undertaken by NSW Water Solutions and the following description of this method is provided by Cloke (undated).
The procedure for sizing water supply systems on a security of supply basis (secure yield) arose from experiences during the severe 1979 to 1983 drought. Previous methods of sizing did not reflect the performance of the system as perceived by the consumer who tends to view the system’s performance in terms of annual water charges and the frequency, duration and severity of restrictions on the use of water.
The key considerations for the procedure were that: • it is neither practical, economic nor environmentally responsible to provide “restriction free” water supply systems; • a trade-off is necessary between the security of supply provided (i.e. the relative lack of restrictions) and the associated capital and operating costs; • they should allow comparison of alternative water supply schemes which are operationally satisfactory (i.e. restrictions are not of excessive frequency, duration or severity); and • adequate storage should be available to allow the operating authority to manage the scheme during drought periods.
The procedures result in a defined term called “Secure Yield”. The secure yield is considered to be the annual demand that can be supplied from the system while satisfying the following conditions: a) Duration of restrictions does not exceed 5% of the time; b) Frequency of restrictions does not exceed 10% of years (i.e. 1 year in 10 on average); and c) Severity of restrictions does not exceed 10%. Systems must be able to meet 90% of the unrestricted water demand (i.e. 10% average reduction in consumption due to water restrictions) through a repetition of the worst recorded drought, commencing with the storage drawn down to the level at which restrictions need to be imposed to satisfy a) and b) above.
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Secure yield is defined as the highest annual water demand that can be supplied from a water supply system while meeting the above 5/10/10 rule.
The above guidelines for sizing of water supply systems on a security of supply basis were developed to enable sizing and comparison of alternative water supply schemes that should be satisfactory from an operational point of view. The guidelines seek to provide schemes that are operationally satisfactory so that: • restrictions are neither of excessive duration nor too frequent; and • adequate capacity is available to allow the operating authority to manage the scheme during drought periods.
Previously, secure yield was based on a ‘5/10/20 rule’. This meant that a 20% reduction in consumption would be required through a repetition of the worst recorded drought. State Government performance monitoring data shows that the overall water consumption has fallen and it is considered that it would be much more difficult to achieve a 20% reduction in consumption than it was 20 years ago. Accordingly, in February 2009 the NSW Office of Water agreed to base future planning in non- metropolitan NSW on being able to achieve an average of a 10% reduction in consumption through a repetition of the worst drought commencing with the storage already drawn down to satisfy the restriction duration and frequency criteria in a) and b) above. Thus the NSW ‘5/10/20 rule’ has been superseded by a ‘5/10/10 rule’.
The level of security that is appropriate for sizing of headworks for country water supplies may vary with the size of the town, the nature of its industries and the cost of providing that security. The duration, frequency and level of restrictions implied by the 5/10/10 rule are considered to be a reasonable basis for sizing of water supply headworks on a security of supply basis.
2.2.2 BASELINE SECURE YIELD
Numerous secure yield runs have been undertaken by NSW Public Works (NSW Water Solutions) during the course of the IWCM Evaluation Study and investigations of alternate water sources.
The initial secure yield analysis was reported in February 2008, which indicated the existing catchment with a Suma Park Reservoir volume of 18,000 ML had a secure yield of 3,500 ML/year. This was based on the 5/10/20 rule. This was the first report that showed a dramatic reduction from the secure yield calculated in 1990 of 7,800 ML/year.
The 2008 analysis used an extended climate data set that covered the period 1890 to 2007. The dramatic reduction in the calculated secure yield was put down to the influence of the Federation Drought (1895 to 1902). If the Federation Drought period is removed from the analysis, the secure yield is 4,500 ML/year (based on 5/10/20 rule).
In November 2009, some sensitivity testing was undertaken that examined the impact of the frequency and duration of restrictions. Based on the results of this analysis and consideration of the influence of the Federation Drought, it was considered that the base secure yield of 3,500 ML/year from the February 2008 report was too conservative, and Council adopted a figure of 4,000 ML/year. This was reported in the Water Projects Updated Report – November 2009 (Orange City Council, 2009).
Bathymetric survey of Suma Park Reservoir was completed in July 2010. This revealed that the volume at Full Supply Level (FSL) is 17,290 ML (i.e. 710 ML less than used in the secure yield modelling).
Around the same time, Council was considering raising Suma Park Dam in conjunction with dam safety upgrade works. Secure yield analyses were undertaken to examine the effect of increasing the volume of Suma Park Reservoir using the 5/10/20 rule with the following results: • Suma Park Reservoir volume 17,290 ML (existing): secure yield = 3,450 ML/year; • Suma Park Reservoir volume 18,970 ML (1.0 m raise): secure yield = 3,600 ML/year; and • Suma Park Reservoir volume 20,760 ML (2.0 m raise): secure yield = 3,800 ML/year.
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This showed that increasing the dam FSL by 1.0 m from the existing FSL would increase the secure yield by 150 to 200 ML/year.
Further secure yield modelling was undertaken for a Suma Park Reservoir volume of 18,970 ML (i.e. assuming a 1.0 m raise) based on the 5/10/20 rule. This gave a value of 3,600 ML/year which was reported in the Water Strategy Update Report – December 2010 (Orange City Council, 2010).
The increased dam volume (i.e. 1.0 m raise) was then analysed using the 5/10/10 rule (which is now being adopted for all secure yield analyses) and the secure yield was found to be 3,400 ML/year. Therefore, adopting the 5/10/10 rule reduced the secure yield by 200 ML/year compared to the 5/10/20 rule for a Suma Park Reservoir volume of 18,970 ML.
Further analyses were based on a Suma Park Reservoir volume of 18,970 ML (i.e. assuming a 1.0 m raise) as various options were assessed.
At the time of preparation of the August 2011 report titled Orange Emergency Drought Connection Macquarie Pipeline Update (Orange City Council, 2011) there had been no secure yield analysis of the existing Suma Park Reservoir volume (i.e. 17,290 ML) using the 5/10/10 rule. Therefore based on the relationship derived from the 5/10/20 modelling for the three different Suma Park Reservoir volumes, it was assumed that the secure yield for the existing reservoir volume would be 3,250 ML/year (i.e. 150 ML/year less than that determined for a 1.0 m raise).
Further secure yield assessment was undertaken in September 2011 that examined a range of water supply options, three Suma Park Reservoir volumes (existing, 1.0 m and 2.0 m raises) and modified environmental flow rules. In addition, the operating rules associated with Gosling Creek Dam were reviewed and added to the analysis.
The September 2011 analysis adopted the 5/10/10 rule and gave the following results: • Suma Park Reservoir volume 17,290 ML (existing): secure yield = 3,400 ML/year; • Suma Park Reservoir volume 18,970 ML (1.0m raise): secure yield = 3,600 ML/year; and • Suma Park Reservoir volume 20,760 ML (2.0m raise): secure yield = 3,800 ML/year.
Therefore, the secure yield for the existing catchment, Gosling Creek and Spring Creek reservoirs and Suma Park Reservoir with a volume of 17,290 ML, based on the 5/10/10 rule is 3,400 ML/year.
2.2.3 5/10/10 VS 5/10/20
As discussed above, the secure yield modelling was initially based on a 5/10/20 rule. This meant that a 20% reduction in consumption would be required through a repetition of the worst recorded drought. However, in accordance with best practice, Orange City Council adopted the 5/10/10 rule which is now included in Council’s water supply level of service.
The secure yield modelling undertaken in the early part of the IWCM Evaluation Study has provided results that can be compared to see the effect of the two rules. These results are summarised in Table 2.1 along with the assumptions used for each modelling run.
Table 2.1 – Comparison of secure yield rules
Secure Yield, ML/year Secure yield assumptions 5/10/20 5/10/10 Difference
Base system: 3,600 3,400 200 Suma Park Reservoir volume 18,970 ML (1.0 m raise) Spring Creek Reservoir, Gosling Creek Reservoir
Base system plus: 5,400 5,000 400 Blackmans Swamp Creek and Ploughmans Creek harvesting on 100% trigger Bores adding 1.1 ML/day
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2.2.4 APPROACH 2.2.4.1 Secure Yield Modelling
NSW Water Solutions have developed a secure yield model for the Orange water supply system. The secure yield model uses climate data for the period 1890 to 2007. The secure yield model includes the surface water catchments of Spring Creek Dam (including Gosling Creek Dam) and Suma Park Dam. This represents the existing natural catchment and water supply system and excludes any external supply sources.
Inflow from additional water sources being considered such as groundwater bores and stormwater harvesting are provided as a daily flow series and water is added from these schemes depending on defined operating rules as detailed below: • Stormwater harvesting – the Orange water balance model (refer to Section 2.3) was used to generate daily stormwater harvesting volumes assuming there is no limitation in the operation of these schemes with regards to the volume in Suma Park Reservoir. The input from these schemes is controlled by the secure yield model with input only being added if the volume in Suma Park Reservoir is less than nominated trigger levels; • Groundwater bores – a constant daily flow based on the volume available from the bores added whenever Suma Park Reservoir is less than 100%; and • Macquarie River to Orange pipeline – the daily river flow series was linked to the secure yield model and water transferred based on defined operating rules, e.g. transfer 12 ML/day whenever the level in Suma Park Reservoir was less than 90% and flow in the river greater than 34 ML/day.
2.2.4.2 Estimated Secure Yield
Not all options were assessed using the NSW Water Solutions secure yield model due to time and budget constraints. Analysis of numerous secure yield model results indicated that it was the federation drought that defined the secure yield for Orange. This was typically a 5.5 to 6 year period from 1894 to 1900 when the combined storage was below full supply level.
An estimate of the potential secure yield increase for an external supply option could be derived by calculating how much additional water the option could have added through the critical drought period and dividing this by the length of the critical drought. The Orange water balance model (refer to Section 2.3) was used for these calculations.
The use of estimated secure yield is noted as required.
2.3 ORANGE WATER BALANCE MODEL
2.3.1 DESCRIPTION
The integrated daily water balance model developed to assess the Blackmans Swamp Creek Stormwater Harvesting Scheme, the Ploughmans Creek Stormwater Harvesting Scheme and other water augmentation schemes being considered by Orange City Council was used for this study. The schematic layout of this model is shown on Figure 1. The integrated water balance model is used to: • Examine various options for supplementing the city’s raw water supplies; • Quantify the expected benefits of each scheme either as a stand-alone project or in combination with other schemes; and • Calculate the changes in downstream flow regimes in the Summer Hill Creek and Ploughmans Creek systems resulting from the various options.
The model uses a daily time step and includes the following main components.
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Catchment Streamflow
Catchment runoff calculations are used to generate a daily streamflow series which is used as inflow to the various storages in the model. The Model for Urban Stormwater Improvement Conceptualisation (MUSIC) is used to generate streamflow for urban areas while the catchment inflow series used for the secure yield modelling is used for the major water supply dams.
Figure 1: Water balance model schematic
Storage Balances
A daily balance is undertaken for each storage (i.e. wetlands, harvest weirs, water storages) in the system using the following: • Inflows - streamflow (which includes spill from upstream storages where applicable) - direct rainfall added to the storage water surface (based on stage-surface area relationships) - inflow from alternate sources such as bores, Macquarie River • Outflows - spill - evaporative losses from the water surface (based on stage-surface area relationships) - extractions (water demand, pumps for harvesting schemes, environmental releases)
Storage at the end of a day is the storage at the start of the day plus the inflows minus the outflows.
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Climate Data
The water system model is used as a tool to compare the performance of various options to supplement the city’s water raw water supplies. The model uses daily rainfall patterns derived from actual rainfall data from 1890 to 2007. This simply means that the modelling compares options assuming that we receive the same rainfall patterns as observed over the past 118 years, for another 118 years. Year 1 in the model is 1890 climate; Year 118 is 2007 climate.
Water Demand
The water balance model includes the water demand for the city.
The water demand in Year 1 of the model was set at 5,400 ML/year (refer to Technical Note 3) and it was assumed to increase with population growth at a rate of 0.8% per annum. The growth rate is based on the medium growth population forecast defined in Technical Note 3.
The daily water demand in the water balance model is restricted in accordance with Council’s adopted water restriction policy that links the level of restriction to the combined water storage volume in Suma Park and Spring Creek Reservoirs.
2.4 CLIMATE CHANGE
While secure yield allows for meeting demand with restrictions through a much worse drought than has occurred since 1890, consideration needs to be given to possible changes from climate change. This study uses the approach proposed in NSW Office of Water’s draft proposed policy for assessing the impact of climate change on non-metropolitan water supplies as described in Samra and Cloke (2010).
Climate change data were obtained from the NSW Office of Water’s 2008 data set which provides historical and future climate change series for the year 2030 based on the A1B warming scenario; a mid-range warming scenario. The following daily climate data were obtained for the catchment: • rainfall; • evapotranspiration; • minimum temperature; and • maximum temperature.
The historical and climate change data sets covered the period January 1986 to December 2006
The approach required four modelling steps: 1. Daily rainfall and evapotranspiration data were used in the secure yield model to produce 15 sets of inflow data for the system storages. 2. Daily rainfall and evapotranspiration data were used in the stormwater harvesting model to produce 15 sets of climate changed daily harvesting values. 3. Daily rainfall, evapotranspiration and temperature data were used in the Scenario B Macquarie River catchment model to produce 15 sets of climate changed daily streamflow at the proposed offtake point for this option. 4. The above data sets were used as input to the Orange secure yield model to determine climate changed secure yield.
It was assumed for the climate change assessment that the inflow from the bores would not change.
The climate change analysis covered the period January 1896 to December 2006 (rather than 1890 to 2007) as it was constrained by the available climate change data.
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Climate change modelling was limited to components of the BAU scenario.
The projected impacts of climate change in 2030 on the average annual rainfall, streamflow and evapotranspiration compared to the historical data sets for Orange are as follows: • Median average annual rainfall is expected to decrease by 2%, with models ranging from a reduction of 7% to an increase of 7%; • Median average annual streamflow is expected to decrease by 15%, with models ranging from a reduction of 31% to an increase of 22%; and • Median evapotranspiration is expected to increase by 2%, with models ranging from no change to an increase of 4%.
2.5 FINANCIAL ANALYSIS
2.5.1 NET PRESENT VALUE
The Net Present Value (NPV) of capital and operating costs were determined for each scheme. The NPV calculations were based on the following assumptions: • 7% discount rate; • 50 year assessment period; • 15% contingency on capital costs; and • 15% cost on capital components for survey, design, engineering and supervision.
All NPV results are presented in $2010/2011.
It should be noted that all cost estimates provided in this document are strategic planning level assessments that would require further refinement during concept and detailed design phases. As such, they should only be relied upon for the purposes of making comparisons between options.
2.5.2 TYPICAL RESIDENTIAL BILL
The Typical Residential Bill (TRB) is defined as follows (Water Services Association of Australia, 2010):
TRB = Residential sewerage charge + residential water fixed charge + special levies + residential water usage charge for the average residential consumption
Orange City Council does not have any special levies for water or sewerage.
A financial model was developed to examine the impact of proposed water security options on the TRB for Orange. A full description of this model is provided in Technical Note 4.
2.6 GREENHOUSE GAS
Operational greenhouse gas emissions were calculated from the estimated electricity consumption which was converted to carbon dioxide equivalents using the NSW Pool Coefficient.
The NSW Pool Coefficient is the average greenhouse gas emissions intensity of electricity sent to customers in the State. For 2011 the Pool Coefficient is 0.975 tonnes of carbon dioxide equivalent per megawatt hour (http://greenhousegas.nsw.gov.au/documents/FS-Comp-PoolCoeff-Oct11.pdf).
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2.7 COMPARISON OF OPTIONS
The above analyses were used to define the following measures for each feasible water supply option: • Capital costs: a direct measure of the estimated capital costs; • Operating costs: a direct measure of the estimated annual operating costs; • NPV – capital costs: the present value of capital costs in $2010/2011 that takes into account timing of capital expenditure; • NPV – operating costs: the present value of operating costs in $2010/2011 that expresses 50 years of operating in current dollars; • Potential increase in secure yield (ML/year); • Total cost of secure yield supplied: this was calculated as the total present value of the option divided by the present value of the secure yield supplied. This measure was derived for capital, operating and total cost. It is used as a measure of the effectiveness of the option with units of $ per ML increase in secure yield; • Change in TRB if adopted: this was the step change in the TRB if the option was implemented within realistic timeframes commencing in 2010/2011; and • Greenhouse gas emissions: calculated for operating power costs only.
In addition to the above measures, comment is provided on potential issues and the likely timeframe to implement each feasible option. The likely timeframe relates to the approval/licensing process as well as construction and commissioning.
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Water Resources
3.1 INTRODUCTION
This section provides a description of water resources that are available in Orange and the surrounding region that could form part of Orange’s water supply system. The section presents assessment of a range of potential water sources which are identified with the following prefixes: • SW – surface water; • SH – stormwater; • RW – rainwater tanks; • GW – groundwater; • E – Effluent; • R – Regional water sources; and • O – Other options including mines and water carting.
Demand management (D) is also considered as an approach to improving the water security.
For each viable water source option, the report provides an assessment of: • how it would work; • the potential increase in secure yield; • the effectiveness of the option; • capital and annual operating cost and NPV; • how the option would impact on the TRB; • potential operational greenhouse gas emissions; and • approvals and licencing requirements, possible issues and likely approvals timeframes.
3.2 SURFACE WATER
3.2.1 INTRODUCTION
Surface water is the primary source of town water supply for Orange. The Orange LGA has six major creek catchments: • Blackmans Swamp Creek; • Ploughmans Creek; • Spring Creek/Brandy Creek; • Gosling Creek; • Upper Summer Hill Creek; and • Lower Summer Hill Creek.
These catchments are shown in Figure 2. All of the catchments, except for Ploughmans Creek, run into the lower Summer Hill Creek catchment and onto Lewis Ponds Creek which joins the Macquarie River. Ploughmans Creek joins with Broken Shaft Creek and then becomes the Bell River. The Bell River joins the Macquarie River at Wellington.
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The major water storage is formed by Suma Park Dam, located on Summer Hill Creek, approximately 4 km east of Orange. The catchment area to Suma Park Dam includes the two other reservoirs (Spring Creek and Gosling Creek) and feeder creeks mostly situated to the south and south-east of the city’s urban area (refer to Figure 2).
3.2.2 GOSLING CREEK DAM 3.2.2.1 Background
The original village of Orange was serviced by water reserves on Blackmans Swamp Creek and private wells. After years of concern over the unreliability of Blackmans Swamp Creek as a water supply, the Council in 1877 attempted to persuade the State Government to finance a more permanent and secure supply of water.
Gosling Creek Dam was constructed in 1890 specifically for the purpose of providing Orange’s first water supply reservoir. The supply was said, then, to be good for the next twenty years.
In 1918 the Meadow Creek system, later renamed Lake Canobolas, was built. Water was pumped to Orange via the 2 ML service tank on Cargo Road, by two pumps powered by coal gas engines. This system was used on a regular basis until about 1935; then on an intermittent basis in dry periods until the end of World War II. Water from both Gosling Creek and Lake Canobolas was unfiltered and untreated and the water quality was poor. It was commonplace at the time for householders to use alum to clarify water before washing clothes.
Gosling Creek Reservoir was not abandoned altogether and did continue to provide the drinking water supply for Bloomfield Hospital. Further, overflow from Gosling Creek Reservoir has, and continues, to drain to Spring Creek Reservoir which remains a functioning component of the city’s drinking water supply scheme.
The Gosling Creek Dam is now used for recreation and irrigation purposes. Newcrest Mining was granted a licence from the Department of Water and Energy in August 2007 to draw water from Gosling Creek Dam up to a maximum volume of 450 ML, for a maximum period of three months. Over this period of time, only 90 ML was utilised.
3.2.2.2 Catchment and Storage Volume
Gosling Creek Dam sits on Gosling Creek south of Orange (refer to Figure 2). The catchment area upstream of the dam is 18.82 km2.
Gosling Creek Dam is a concrete structure with a maximum wall height of 8 m. The reservoir capacity was first calculated in 1890 as 650 ML. However due to silting the reservoir has been recalculated in 2007 to have a capacity of 524 ML. The reservoir has a surface area of about 17 ha at full supply level (FSL).
The stage-storage curve for Gosling Creek Reservoir is provided in Figure 3.
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Figure 2: Surface water catchments
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600
500
400
300 Storage Volume, ML Volume, Storage
200
100
0 0 1 2 3 4 5 6 7 Stage, m
Figure 3: Gosling Creek Reservoir stage-storage curve
3.2.2.3 Dams Safety Act, 1978
Gosling Creek Dam is a prescribed dam under Schedule 1 of the Dams Safety Act, 1978. The Dams Safety Committee (DSC) can require owners of prescribed dams to do things to ensure the safety of their dams.
Gosling Creek Dam has the following consequence categories: • Sunny Day Consequence Category (SDCC) Low • Flood Consequence Category (FCC) Significant
The latest dam surveillance report was completed in 2005 and found that the dam is performing satisfactorily.
3.2.2.4 Operation
Water can be drawn through two floating trunnions (300 mm and 450 mm in diameter) into a 600 mm diameter outlet pipe controlled by a 450 mm valve located on the downstream side of the wall. Water can be drawn from the storage at a set level below the fluctuating storage level. There is a 600 mm scour valve below the outlet pipe and pump which supplies the irrigation system for the recreation reserve. The service main control and scour valves are operated from ground level and cannot be operated when the reservoir is above dam crest level and spilling.
Gosling Creek Reservoir is part of the Orange water supply system with water transferred in very specific circumstances. Specifically, water is transferred from the reservoir to Spring Creek Reservoir according to the following rules: • Release trigger – water is transferred when the combined storage levels of the city’s two main reservoirs (Suma Park and Spring Creek Reservoirs) are at or estimated to reach 25% of their full supply level within the short term based on existing drawdown rates of the city’s combined water supplies; and
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• Cease release trigger – transfer stopped when the storage in Gosling Creek Reservoir reaches 50%.
The above rules provide access to about 262 ML of stored water plus any inflows occurring at the time.
The cease release trigger is based on a Council resolution. However an environmental impact assessment undertaken for the emergency transfer of water in 2009 found that the storage could be drawn down to 10% without significant adverse environmental impact (Geolyse, 2009a). This would provide access to a further 150 ML of stored water (plus any inflows occurring at the time).
3.2.2.5 Options for Additional Water Supply
Gosling Creek Dam forms the upper most storage in the system and therefore fills first in response to catchment runoff before spilling to Spring Creek Reservoir. Stored water is used when the city’s main storages are drawn down.
There are no realistic options for increasing the capacity of Gosling Creek Reservoir, or significant benefits in operating the storage in a different manner.
3.2.3 SPRING CREEK DAM 3.2.3.1 Background
Spring Creek Dam was constructed in 1931 along with the Spring Creek Water Treatment Plant (WTP) and became the main water supply for Orange at the time. Sixteen years later, in 1947, the Spring Creek Dam wall was raised and, following a partial embankment failure in 1966, reconstruction work was undertaken and completed in 1969.
Spring Creek Reservoir was drawn down in March 2000 to allow safety upgrade works to be undertaken on the main embankment and spillway. These works were completed in March 2007. The Spring Creek WTP was decommissioned in 2000 as it was unable to access water from the storage during the dam upgrade works. This plant is unlikely to be used again.
3.2.3.2 Catchment and Storage Volume
Spring Creek Dam is located at the junction of Spring Creek and Gosling Creek, downstream of Gosling Creek Dam (refer to Figure 2). Inflow to Spring Creek Reservoir includes Gosling Creek (the overflow from Gosling Creek Dam), Brandy Creek and Spring Creek. The catchment area upstream of the dam is 65.57 km2 which includes the Gosling Creek Dam catchment.
Spring Creek Dam is a composite dam, consisting of an earth fill embankment with a concrete core and has a height of 16 m and a crest length of 206 m. The dam has a storage capacity of 4,449 ML and surface area of 97.5 ha at FSL.
The stage-storage curve for Spring Creek Reservoir is provided in Figure 4.
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4500
4000
3500
3000
2500
2000 Storage Volume, ML Volume, Storage
1500
1000
500
0 0 2 4 6 8 10 12 Stage, m
Figure 4: Spring Creek Reservoir stage-storage curve
3.2.3.3 Dams Safety Act, 1978
Spring Creek Dam is a prescribed dam under Schedule 1 of the Dams Safety Act, 1978. The Dams Safety Committee (DSC) can require owners of prescribed dams to do things to ensure the safety of their dams.
Spring Creek Dam has the following consequence categories: • SDCC High C • FCC High C
The latest dam surveillance report was completed in 2001 and found that while the dam was performing satisfactorily there could be no guarantee that this would continue into the future. A concept design report was subsequently completed to address safety issues and upgrading works completed in 2007.
3.2.3.4 Operation
The Spring Creek WTP sourced raw water from the reservoir, treated and distributed this water to the water reticulation system. This plant had a capacity of 10 ML/day but was decommissioned in 2000 when the storage was drawn down to facilitate the dam safety upgrade works. Since that time, all potable water has been supplied from the Icely Road WTP.
Spring Creek Reservoir is now operated as part of the combined water storage. Prudent water management maintains stored water higher in the system as it requires energy to move water uphill. Therefore Spring Creek Reservoir is used for water storage with water being transferred to Suma Park Reservoir when the downstream storage falls to less than 25%.
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3.2.3.5 Options for Additional Water Supply
There are no realistic options for increasing the capacity of Spring Creek Reservoir, or significant benefits in operating the storage in a different manner.
A feasibility study for de-silting the storage on the back end of the upgrade works and while the reservoir was essentially empty was undertaken in March 2007 (Geolyse, 2007). Undertaking this activity would increase the dam storage capacity and the conditions under which this activity could be physically undertaken are infrequent and short lived – that is, it was seen as opportune while the dam was empty, which (hopefully) would not occur again within the short term.
De-silting the dam would entail removal of the sediment deposited on top of the (then) natural ground surface since the dam was built. The rate and concentration of deposition would vary spatially; with a concentration closer to the original stream beds and behind the wall. Test pits were excavated across the floor of the storage and it was estimated that the de-silting would remove an average of 200 mm across the floor area (approximately 74 ha). This would yield 148,000 m3 of sediment; providing an additional 148 ML of storage: a 3% increase in capacity, the equivalent to about 10 days average water supply for the city of Orange (Geolyse, 2007).
The logistics, costs and approvals process of this operation were considered. It was estimated that the direct economic cost of de-silting 148,000 m3 (in situ) of material ranged from between $3.5 to $5.3 million. This equates to a cost of between $22,680 and $35,760 for each additional megalitre of storage obtained.
Secure yield modelling undertaken for the IWCM Evaluation Study for the raising of Suma Park Dam (refer to Section 3.2.4.5) shows that storage volume increases of over 1,600 ML only increased the system secure yield by around 200 ML/year. Based on this result, the potential 148 ML additional storage gained by de-silting Spring Creek Reservoir would not have a significant impact on the system secure yield.
The option of de-silting Spring Creek Reservoir (Option SW8) was ruled out at the time the storage was drawn down. It would be even more expensive to do now that the dam is full.
3.2.4 SUMA PARK DAM 3.2.4.1 Background
Persistent water shortages remained following the increase in capacity of Spring Creek Reservoir. A new dam, Suma Park Dam, was constructed on Summer Hill Creek to the north-east of the city. This dam was completed in 1962 and provided a reservoir with a capacity of 18,100 ML (see comment below regarding revised storage volume).
The Icely Road WTP was completed in 1959 and sourced its raw water from the Suma Park Reservoir. The capacity of the Icely Road WTP was increased in 1966 to 20 ML/day. More works commenced in 1981 to double the capacity of the Icely Road WTP with construction completed in 1985. It now has a capacity of 38 ML/day and is the main water treatment plant for the city’s water supply system.
Suma Park Dam creates the main water supply reservoir for Orange.
3.2.4.2 Catchment and Storage Volume
Suma Park Dam is located on Summer Hill Creek approximately 2.5 km upstream of its confluence with Blackmans Swamp Creek (refer to Figure 2). Inflow to Suma Park Reservoir includes Gosling Creek (the overflow from Spring Creek Dam), Dairy Creek and Summer Hill Creek. The total catchment area upstream of the dam is 178.49 km2 of which 112.92 km2 (63%) is downstream of the Spring Creek Dam catchment.
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Suma Park Dam has the following components: • a main dam consisting of a 30.5 m high concrete arch dam with a central ungated spillway. The crest length of the main wall is about 208 m. Discharge over the spillway is dissipated in a plunge pool at the base of the dam; • a 6 m high, 160 m long earth fill saddle dam located about 400 m west of the main dam; and • outlet works consisting of an intake tower about 5 m upstream of the main dam wall that conveys water to the pump station approximately 300 m downstream which delivers water to Icely Road WTP.
Initial stage-storage data showed that Suma Park Reservoir stored approximately 18,100 ML at FSL. A detailed bathymetric survey was undertaken in July 2010 and a new stage-storage curve developed for the reservoir. Further detailed survey was conducted on the main wall and spillway section as part of the safety upgrade works. This determined that the minimum spillway level is RL 842.31 m AHD. From this data the revised capacity of Suma Park Reservoir at FSL is 17,290 ML.
The original and revised stage-storage curves for Suma Park Reservoir are shown in Figure 5. The revised data shows that the storage has a surface area of 159.5 ha at FSL.
Revised Data (2010) Original Data
20000
18000
16000
14000
12000
10000
Storage Volume, ML Volume, Storage 8000
6000
4000
2000
0 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 Stage, m
Figure 5: Suma Park Reservoir stage-storage curve
3.2.4.3 Dams Safety Act, 1978
Suma Park Dam is a prescribed dam under Schedule 1 of the Dams Safety Act, 1978. The Dams Safety Committee (DSC) can require owners of prescribed dams to do things to ensure the safety of their dams.
Suma Park Dam has the following consequence categories: • SDCC High B • FCC High B
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The latest dam surveillance report was completed in 2001 and found that while the dam was performing satisfactorily there could be no guarantee that this would continue into the future. The spillway capacity of Suma Park Dam does not meet standards recommended by the NSW Dam Safety Committee (NSW DSC) and the Australian National Committee on Large Dams (ANCOLD) therefore an upgrade to the dam is planned.
3.2.4.4 Suma Park Dam Upgrade
Engineering consultants are currently undertaking the concept, detailed design and documentation for the safety upgrade works. Council is seeking a realistic, innovative, cost-effective solution to address the risks presented by Suma Park Dam in both the short and long term by combining a staged construction approach with an effective flood warning system.
Upgrade of the dam will be undertaken in two stages: • Stage 1: upgrade of the dam to achieve appropriate capacity within the dam to safely pass the 1 in 1,000,000 Annual Exceedance Probability (AEP) flood (note that this was originally to upgrade the dam to safety pass the 1 in 100,000 AEP flood; however this was revised to the 1 in 1,000,000 AEP flood after a review of the catchment hydrology); and • Stage 2: works to achieve a negligible risk level with regards to dam safety.
The concept and detailed design work is addressing Stage 1 of the dam upgrade works.
A review of the catchment flood hydrology was completed as part of the concept phase. This demonstrated that the upgraded Spring Creek Dam has a significant effect on attenuating flood inflows to Suma Park Dam. It was therefore feasible to upgrade the spillway of Suma Park Dam to accommodate the 1 in 1,000,000 year flood for the Stage 1 upgrade. The concept design for the Stage 1 upgrade includes (Entura, 2011a): • Stage 1A: a 2.3 m high parapet wall on the downstream side of the crest of the non-overflow sections of the main concrete wall; and • Stage 1B: a three bay fuseplug spillway at the location of the saddle dam up to 5.25 m high.
The estimated project costs for these stages are: • Stage1A $2.7 million • Stage 1B $5.4 million • Total Stage 1 $8.1 million
Earthquake analysis demonstrated that the upgraded dam would retain a sufficient factor of safety following damage from the maximum design earthquake and that no additional strengthening was required. It was concluded that at the completion of Stage 1A and Stage 1B works the dam will satisfy the NSW DSC’s requirements for negligible dam safety risk with no further upgrade (Entura, 2011a). In effect, the Stage 2 objectives have been achieved with the Stage 1 works and no further works are required.
3.2.4.5 Raising Suma Park Dam
Description
Following review of the concept design prepared for the Stage 1 upgrade works, Council commissioned an assessment of the technical, cost and program implications of raising the FSL of Suma Park Dam. This assessment examined the implications of a 1.0 m and 2.0 m increase in FSL (Entura, 2011b).
The main findings from this assessment are (Entura, 2011b): • a 1.0 m raising of FSL by raising the concrete spillway and providing a larger fuse plug auxiliary spillway poses no insurmountable technical issues;
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• raising the FSL by greater than 1.0 m should not be considered as the stresses in the existing concrete arch dam wall would exceed allowable limits; • raising the FSL by 1.0 m inundates properties not belonging to Council and land acquisition would be required; • an Environmental Impact Statement (EIS) is likely to be required to identify any environmental issues and obtain the required statutory approvals for raising the FSL; and • the EIS and property acquisition is likely to take a minimum of 12 months.
The estimated capital costs of including a 1.0 m increase in the FSL in association with the Stage 1 dam safety upgrade works gave the following cost breakdown: • Stage1A $4.1 million • Stage 1B $6.9 million • Total Stage 1 $11.0 million
With an allowance for an additional $0.65 million for approvals and land acquisition, the additional cost to increase the FSL by 1.0 m is $3.55 million.
A 2.0 m increase would cost an additional $6.86 million; however as noted above, a 2.0 m increase in FSL is not technically feasible and no more than a 1.0 m increase should be considered for the dam (Entura, 2011b).
There would be no annual operating costs for the dam raising option, apart from routine dam maintenance and inspection which is already undertaken.
Raising Suma Park Dam is included in Council’s BAU scenario.
Assessment of Secure Yield
The benefit of increased storage capacity in Suma Park Reservoir was assessed using secure yield modelling. This assessment considered: • inflow from the existing catchment; • the potential input from other external catchment water sources including bores, stormwater harvesting and the proposed Macquarie River to Orange pipeline; and • possible changes in environmental flow releases from Suma Park Dam.
The secure yield analyses used the following Suma Park Reservoir volumes: • Current spillway level (842.31 mAHD); volume = 17,290 ML • Raise 1.0 m (843.31 mAHD); volume = 18,970 ML • Raise 2.0 m (844.31 mAHD); volume = 20,760 ML
Suma Park Dam is licenced under Part II of the Water Act, 1912. Condition (6) of the current licence (80SL046857) includes an environmental flow release requirement as follows:
(6) Subject to condition (7), the licensee shall release into the watercourse downstream of the dam a flow of water equivalent to 12 litres per second or to the flow entering the storage of the dam for the time being, whichever is the lesser.
The licence is currently being reviewed as part of the public enquiry being handled by the Orange District Land Board. The draft licence proposes an amendment to condition (6) as follows:
(6) Subject to condition (7), the licensee must release into the watercourse downstream of the dam a flow of water equivalent to 2 megalitres per day for a total of 176 consecutive days commencing 1 November each year and ending 25 April each following year (being a total of 352 megalitres).
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These two conditions were assessed in the secure yield modelling as Environmental Flow Rule (EFR) 1 and 2 respectively.
The secure yield analysis included input from a number of external sources in addition to the natural catchment inflow. The results presented include input from the external sources listed in Table 3.1.
Table 3.1 – Supply from external sources for assessment of raising Suma Park Dam
Variable
BSC100PC/100 Daily input from the Blackmans Swamp Creek and Ploughmans Creek stormwater harvesting schemes added to Suma Park Dam whenever the storage in the dam is less than 100%
Bores75 (1) A daily inflow of 0.2 ML/day to Suma Park Dam only when the storage is less than 100%
MR12/30 (2) Add 12 ML/day to Suma Park Dam when: 1. Volume in Suma Park Dam is <90%; and 2. Flow in the Macquarie River is > 30 ML/day
Bores300 An additional inflow from the bores of 0.62 ML/day to Suma Park Dam only when the storage is less than 100%. This is additional to Bores75 i.e. the total bore inflow is 0.82 ML/day (or 300 ML/year).
BSC2 Daily input from the Blackmans Swamp Creek Stage 2 and Ploughmans Creek stormwater harvesting schemes added to Suma Park Dam whenever the storage in the dam is less than 100%
Lake Rowlands Adding a daily inflow of 2.66 ML/day (972 ML/year) to Suma Park Dam only when the storage is less than 100%
(1) At the time of undertaking this assessment, the existing groundwater bores were licensed to extract 75 ML/year. New licences were granted in early 2012 increasing the annual extraction limit to 462 ML/year. (2) At the time of undertaking this assessment, The Macquarie River to Orange pipeline was being assessed using the 12/30 rule as described. This rule was revised to the 12/34 rule during the hydrology study competed as part of the Environmental Assessment being undertaken for that scheme.
Table 3.2 provides a summary of the secure yield modelling results for raising Suma Park Dam. This table lists the variables and assumptions for each model run. All results are based on the 5/10/10 rule.
The results show the following: • Raising Suma Park Dam by 1.0 m above the current spillway level increases the secure yield for the system by 100 to 200 ML/year (i.e. comparison of Run 1-1 and Run 1-4; comparison of Run 2-1 and Run 2-2; comparison of Run 6-1 and Run 6-4); • Raising Suma Park Dam by 2.0 m above the current spillway level increases the secure yield for the system by 400 ML/year (i.e. comparison of Run 1-1 and Run 1-3); and • EFR 2 reduces the secure yield by 100 to 200 ML/year (i.e. comparison of Run 1-2 and Run 1 4; comparison of Run 4-2 and Run 4-7; comparison of Run 6-2 and Run 6-4).
Raising Suma Park Dam could increase the secure yield of the system by up to 400 ML/year for 2.0 m increase. However, as determined by the engineering consultants through the feasibility assessment (Entura, 2011b), an increase of 2.0 m is not technically feasible. Therefore the potential increase in secure yield by raising Suma Park Dam by 1.0 m is 100 to 200 ML/year.
The increase in secure yield gained by the 1.0 m raise is essentially “lost” by the proposed new environmental flow rule. However, this new environmental flow rule is being negotiated as part of securing a licence for the permanent operation of Stage 1 of the Blackmans Swamp Creek stormwater harvesting scheme. The secure yield increases from 3,400 to 4,650 ML/year by raising the dam by 1.0 m and adding the harvesting scheme inflow; an increase of 1,250 ML/year. Therefore the net increase in secure yield by being able to operate the harvesting scheme full time is around 1,100 ML/year.
Finally, it is noted that the increase in secure yield determined by this assessment is consistent with the assessment undertaken for the Suma Park Dam Augmentation EIS (SMEC, 2003). At that time, a 1.80 m increase in FSL was proposed, which increased the secure yield by 400 ML/year.
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Table 3.2 – Secure yield results for raising Suma Park Dam
External Water Input to Suma Park Dam
Suma Secure Park Yield,
Run Dam EFR Volume,
ML ML/year Natural BSC100/PC100 Bores75 MR12/30 Bores300 BSC2 Lake Rowlands
1-1 17,290 1 3,400
1-2 18,970 2 3,400
1-3 20,760 1 3,800
1-4 18,970 1 3,600
2-1 17,290 1 4,500
2-2 18,970 1 4,650
2-3 20,760 1 4,900
3-1 17,290 1 4,600
3-2 18,970 1 4,750
3-3 20,760 1 5,000
4-1 17,290 1 6,200
4-2 18,970 2 6,200
4-3 20,760 1 6,600
4-7 18,970 1 6,350
5-1 17,290 1 6,450
5-2 18,970 1 6,600
5-3 20,760 1 6,850
6-1 17,290 1 7,400
6-2 18,970 2 7,400
6-3 20,760 1 7,750
6-4 18,790 1 7,500
8-1 17,290 1 8,500
8-2 18,970 1 8,550
8-3 20,760 1 8,700
Storage Required
Secure yield modelling can be used in two ways: 1. It can determine the secure yield for a given system based on defined operating rule – this is how the model was used to generate the results presented in Table 3.2 – the storage available and the various inputs to the storage are defined; or 2. It can determine the storage required to meet a defined secure yield.
The secure yield model was run using the latter method to determine the storage required to meet secure yields ranging from 5,400 ML/year (the current estimated unrestricted water demand) to 7,800 ML/year (the volumetric licence limit for town water supply). The projected annual water demand in 2040 under a BAU scenario is between 6,060 and 6,655 ML/year.
PAGE 23 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
The analysis was undertaken for two system inflow conditions (refer to Table 3.1 for definitions): • Inflow 1: the existing catchment, BSC100/PC100 and Bores75 (this is nominally called the “current” inflow but is subject to the granting of licences for the Blackmans Swamp Creek stormwater harvesting scheme); and • Inflow 2: the existing catchment, BSC100/PC100, Bores75 and MR12/303.
The existing environmental flow rule was assumed for the analysis and there was no allowance for potential climate change impacts.
The relationship between storage and secure yield is displayed on Figure 6 which shows the following: • Suma Park Reservoir would need to have a capacity of about 24,000 ML to provide a secure yield that meets the current estimated unrestricted demand of 5,400 ML/year with the current inflow. This would require an increase in the FSL of around 3.6 m; • Suma Park Reservoir would need to have a capacity of around 45,000 ML to provide a secure yield that meets the estimated demand in 2040 with the current inflow; • Increasing inflow to the system reduces the storage required to meet a defined secure yield. For example, a Suma Park Reservoir capacity of 12,850 ML meets the current estimated unrestricted demand of 5,400 ML/year with the current inflow plus the addition from the Macquarie River to Orange pipeline; and • Suma Park Dam would need to have a capacity of around 25,000 ML to provide a secure yield that meets the estimated demand in 2040 with the current inflow plus the addition from the Macquarie River to Orange pipeline.
Discussion
A 1.0 m raise in the FSL of Suma Park Dam does not have a significant impact on the secure yield only providing an increase in secure yield of 100 to 200 ML/year. The reason for this small increase is illustrated in Figure 7 for the critical drought period. Raising the dam by 1.0 m increases the storage volume by 1,680 ML; this amount of additional supply is available at the start of the drought period. Inflow to the storage does not change through the drought period. Therefore, the additional volume provided by raising the dam that is available at the start of a drought period is “used up” throughout the drought period by increased annual demand and additional evaporation losses. This is demonstrated in Figure 7 as the two storage lines gradually converge. Therefore the additional volume is not available every year; it is used over the drought period when the storage is less than full.
Secure yield is a function of inflow, storage volume and demand. Increasing the storage volume does not increase the inflow. Therefore the system responds better to additional inflow rather than additional storage and options that increase inflow to the system improve the secure yield more than increasing the FSL by 1.0 m.
3 The 12/30 operating rule for the Macquarie River pipeline has been replaced with a 12/34 operating rule – refer to Section 3.2.6.
PAGE 24 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Inflow 1 Inflow 2
60000
50000
40000
30000 Suma Park Dam Storage, ML Storage, Dam Park Suma 20000
10000
0 5000 5500 6000 6500 7000 7500 8000 Secure Yield, ML/year
Figure 6: Suma Park Dam storage-yield curve
Suma Park Dam 17,290 ML; Annual Demand = 3,400 ML/year Suma Park Dam 18,970 ML; Annual Demand = 3,600 ML/year
20000 Additional volume provided by raising Suma Park Dam 18000 by 1.0m = 1,680 ML
16000
14000 Length of critical drought = 5.5 years
12000
10000 Volume, ML Volume, Additional storage volume used to 8000 supply an increased demand over the critical drought period. Rate of storage draw-down is quicker with 6000 higher annual demand.
4000 Additional storage used over the 5.5 year period to supply increased demand 2000 and losses (more evaporation losses) to end up at about the same minimum storage volume. 0 1894 1895 1896 1897 1898 1899 1900 Year
Figure 7: Modelled additional Suma Park Dam storage during critical drought period
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3.2.4.6 Summary
Raising Suma Park Dam FSL by 1.0 m is a technically feasible option that can increase the secure yield. A 2.0 m increase in FSL is not technically feasible and no more than a 1.0 m increase should be considered for the dam.
Table 3.3 summarises the option of raising Suma Park Dam by 1.0 m. This option is subject to further detailed design, environmental assessment, approvals and licensing that may change the assessment.
Table 3.3 – Summary of Option SW1: raise Suma Park Dam by 1.0 m
Measure Result
Capital cost, $ $3,550,000
Operating cost, $/year Nil
NPV – capital cost, ($2010) $3,550,000
NPV – operating cost, ($2010) Nil
Potential increase in secure yield, ML/year 100 to 200
Capital costs, $/ML increase in secure yield $1,202 to $2,404
Operating costs, $/ML increase in secure yield Nil
Total cost of secure yield supplied, $/ML increase in secure yield $1,202 to $2,404
Change in TRB if adopted $9 per assessment
Greenhouse Gas Emissions (operating power only) Nil
Issues to consider • Environmental approvals requiring an EIS • Licensing • Likelihood of change to environmental flow rules • Land ownership
Likely timeframe to complete 3 years
3.2.5 LAKE CANOBOLAS 3.2.5.1 Description
Lake Canobolas, previously known as Meadow Creek Water Supply, was constructed in 1918 and is fed by Molong Creek. The original Lake Canobolas pump station was commissioned in 1918 with a double cylinder gas engine driving two pumps, and ceased operation in 1957. This pump was restored in 1988 with a new electric motor; however it still does not have the capacity to deliver water to Orange. The mains from the lake are 300 mm diameter cast iron and run for 3.04 km to a 2 ML reservoir on Cargo Road. There are 25 service connections off the mains.
A smaller pump station delivers water to Nashdale through 100 mm diameter water meter. Nashdale consume approximately 40 ML/year from Lake Canobolas.
Downstream of Lake Canobolas, Molong Creek heads in a northerly direction. It is joined by a minor tributary, Heifer Station Creek which also has its headwaters on the slopes of Mount Canobolas, before reaching Molong Dam.
Molong Dam has a capacity of 1,000 ML and is used as the major source of water for Molong. Approximately 240 to 300 ML/year is drawn from the storage for municipal water supply purposes. The total catchment area to Molong Dam is 74 km2 (including the Lake Canobolas catchment). The catchment downstream of Lake Canobolas is predominately open rural grazing and cropping land.
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3.2.5.2 Catchment and Storage Volume
The Molong Creek catchment rises on the eastern slopes of Mount Canobolas. Its headwaters include a mixture of forested and cleared pastureland. Lake Canobolas is situated quite high in the catchment with a catchment area of 21.81 km2. The lake itself has a volume at spillway level of 483 ML. It supplies a small volume of water to some local water users (about 40 ML/year) and is now predominately used for recreational activities.
3.2.5.3 Options for Water Supply
Lake Canobolas as a Permanent Component of the Supply System
Orange City Council examined an option to use water sourced from Lake Canobolas to supplement the city’s raw water supplies. The proposed scheme was assessed using the following operating rules: • Extract up to 2 ML/day whenever the volume of water stored in Lake Canobolas is within 2.0 m of the spillway (i.e. whenever the storage is above 245 ML or 51% of capacity); and • Only transfer water from Lake Canobolas whenever Suma Park Reservoir is less than 18,000 ML (i.e. less than 99.45% of capacity).
Conceptually, water from Lake Canobolas would be transferred to Spring Creek Reservoir or the filtration plant (refer to Figure 8).
Figure 8: Lake Canobolas connection options
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Table 3.4 summarises how much water this could add to the city’s raw water sources. Supplying an average of 283 ML/year represents about 5% of the city’s current unrestricted average annual water demand.
Table 3.4 – Lake Canobolas scheme performance
Measure Value
Average yield, ML/year 283
Minimum yield Nil
Maximum yield (1953), ML/year 612
Number of years of zero transfer in 118 modelled 8
Secure yield modelling of this option showed that the addition of this source on its own it did not increase the system secure yield. When combined with Blackmans Swamp Creek stormwater harvesting the addition of water from Lake Canobolas increased the secure yield by 100 ML/year. The reason for this is that the supply of water from Lake Canobolas is largely based on natural catchment runoff. During drought conditions when inflow to Spring Creek Reservoir and Suma Park Reservoir is low, likewise, inflow to Lake Canobolas is low. In these drought periods the amount of water available from Lake Canobolas is relatively minor.
Further investigation into the use of Lake Canobolas as a water supply dam highlighted approval and licensing issues (Swan Environmental, 2011). The dam is no longer classified as a water supply storage and the current plan of management is for a recreational lake. Operation of the storage based on the above rules would impact on the lake storage levels with the average lake level being somewhat lower than its current average level. Substantial work would be required to obtain a licence to extract water for town water supply purposes including dam safety upgrade works to comply with DSC requirements and full environmental assessment. These works have been estimated at $15 million (Swan Environmental, 2011).
Emergency Supply System
The option of connecting Lake Canobolas to the Cargo Road reservoir was identified for use in emergencies (when the city’s combined storages are less than 25%). This system would require: • a new pump station at Lake Canobolas; • a new rising main to Cargo Road reservoir; • a booster pump station at Cargo Road reservoir; and • a rising main to connect to the dual water main (refer to Figure 8).
The concept is that raw water from Lake Canobolas would be pumped through the dual water main around to the stormwater harvesting infrastructure and from there to Suma Park Reservoir. This option is estimated to have capital costs of $500,000 and could be implemented in a relatively short timeframe.
3.2.5.4 Estimated Cost
Lake Canobolas as a Permanent Component of the Supply System
The estimated capital costs to provide a transfer system from Lake Canobolas to Spring Creek is $3.325 million. Annual operating costs to transfer an average of 283 ML/year are $77,000 (power and maintenance costs).
Emergency Supply System
The construction of a pipeline and pump station to allow use of water from Lake Canobolas for emergency supplies is estimated to have capital costs of $500,000.
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3.2.5.5 Summary
Table 3.5 summarises the option of using Lake Canobolas as part of the water supply system.
Table 3.5 – Summary of Option SW2: Lake Canobolas
Measure Result
Capital cost, $ $3,325,000
Operating cost, $/year $77,000
NPV – capital cost, ($2010) $2,726,000
NPV – operating cost, ($2010) $858,000
Potential increase in secure yield, ML/year 100
Capital costs, $/ML increase in secure yield $1,846
Operating costs, $/ML increase in secure yield $581
Total cost of secure yield supplied, $/ML increase in secure yield $2,427
Change in TRB if adopted $11 per assessment
Greenhouse Gas Emissions (operating power only) 0.27 tonnes CO2e/ML
Issues to consider • Environmental approvals requiring an EIS • Licensing • Required dam safety upgrade works • Limited (if any) secure yield benefit • Social impact on lake recreation/ecology
Likely timeframe to complete 3 to 5 years
The relatively low capital and operating cost of this option returns a reasonable cost per megalitre increase in secure yield and has only a small impact on the TRB. However its low secure yield benefit means that it would need to be coupled with other schemes to meet forecast water demand.
Further, the impact on the lake operating level would have a reasonable impact on recreational activities and there are approval and licensing issues to overcome.
Given the above, Lake Canobolas should not be considered as a permanent component of the long term water security strategy.
The use of Lake Canobolas should be restricted to emergency supplies triggered when the combined storage falls to <25% and used as conditions permit at the time.
3.2.6 MACQUARIE RIVER TO ORANGE PIPELINE 3.2.6.1 Background
The option of a pipeline from the Macquarie River was first considered in the Centroc Water Security Study (MWH, 2009). This study recommended that, in the long term, Orange be connected via pipeline to the Central Tablelands Water system and supplied from an augmented Lake Rowlands dam. The option of a pipeline from the Macquarie River to Orange was not shortlisted as part of the preferred regional water security network as further information or investigation was required. It was recommended that it should be considered as a contingency action for emergency situations (MWH, 2009).
It was recognised in the Centroc Water Security Study that the existing Lake Rowlands dam is unable to supply Orange without impacting on the security of that system until the augmentation is complete. The augmentation of Lake Rowlands is a long-term option that could take between 10 and 15 years to complete.
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The Centroc water security study was completed in October 2009 at which time the Orange City Council water supply was around 30% and the city had been on Level 5 water restrictions since May 2008. Orange City Council formally adopted a comprehensive Strategic Water Supply Strategy at its meeting of 19 December 2009 (Orange City Council, 2009). This plan provided the basis for the management of Orange’s water resources and included a comprehensive range of demand management, local and regional infrastructure, management and funding actions to underpin the sustainable growth of the city for the next 50 years. The 2009 Strategic Water Supply Strategy forms part of Council’s Business as Usual scenario.
An action from this strategy was to (Orange City Council, 2009):
Undertake a detailed feasibility analysis immediately into the establishment of an emergency water supply pipeline connection from the Macquarie River downstream of Bathurst to Orange, and as a secondary option, from Lake Rowlands to Orange (subject to the availability of suitable water volumes and agreement on business arrangements with Central Tablelands Water(CTW)), to confirm concepts and, if suitable, undertake the necessary statutory assessments to prepare for construction in order to optimise delivery of project/s, ideally within 2 years.
Council therefore commissioned further investigations of the Macquarie River pipeline option through the completion of a feasibility study (MWH, 2010) and then concept study (MWH, 2011a). The feasibility study tested the viability of the project compared to a pipeline from Lake Rowlands. Several potential pipe corridors to Orange were investigated. Two of these were from Lake Rowlands and seven from the Macquarie River. The study concluded that the most feasible solution was to bring water to Orange from the Macquarie River via one of two broad potential pipeline corridors with an offtake point located on the Macquarie River downstream of the Turon River confluence. The report found that in order to recommend a preferred corridor, additional engineering and environmental investigations were required.
Following the feasibility assessment, the concept investigation study (MWH, 2011a) compared and evaluated the two pipeline corridor options. A multi-criteria analysis was undertaken and the preferred corridor was recommended. The report also provided a number of recommendations for detailed design.
Council was successful in obtaining $38.2 million of Federal and State government funding for the pipeline project in March 2011. The Macquarie River to Orange pipeline option is currently the subject of ongoing engineering and environmental investigations as part of the design, assessment and approval process.
This section presents a summary of the current knowledge for the Macquarie River to Orange pipeline option. It provides an overview of the system, its operation (as it is currently proposed) and an assessment of its impact on Orange’s water security.
3.2.6.2 Proposed System Overview
The Macquarie River to Orange pipeline is a relatively straight forward water supply option. It involves: • a river offtake structure and extraction pump station on the Macquarie River north of Orange; • a pipeline to connect the river pump station to Suma Park Reservoir (approximately 37 km); and • booster pump stations along the pipeline route.
The proposed pipeline route connecting the Macquarie River to Suma Park Dam is shown in Figure 9.
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A defined operating rule would dictate when pumping could occur. This would be based on a combination of a river flows and available storage in Suma Park Reservoir. The current proposed operating rule, which is subject to change through the detailed design and environmental assessment process, is: • Extract 12 ML/day from the river when: – the flow in the river is greater than 34 ML/day; and – Suma Park Dam storage volume is less than 90%.
This is called the “12/34 rule”.
Source: Geolyse (2012) Figure 9: Proposed Macquarie River pipeline
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3.2.6.3 Catchment and River Flows
The Macquarie River has a catchment area of 7,249 km2 to the proposed river offtake. The catchment area includes the Turon River and the Lewis Ponds Creek system. Figure 10 shows the catchment areas, location of gauging stations along the system and the proposed river offtake structure.
Figure 10: Macquarie River catchments
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There are two active river gauging stations that provide a reasonable amount of historical river flow data: • Macquarie River at Bruinbun (Station 421025) – discharge records 1955 to date; and • Turon River at Sofala (Station 421026) – discharge records 1947 to date.
A flow gauge was operational upstream of the proposed offtake from 1962 to 1978. This gauge was located at the Long Point crossing (about 8.2 km upstream of the proposed offtake point – Dixons Long Point, Station 421080). There is flow data available for the period 1/7/1971 to 11/10/1978 at this site. A new gauge (Macquarie River downstream of Long Point, Station 421192) was commissioned by NOW in June 2011. This gauge is about 4.6 km upstream of the proposed offtake point, but only provides limited historical data.
Modelling of the catchment has been used to develop a long term flow series at the offtake point (Geolyse, 2012). This modelling has used available river flow data and has taken into consideration catchment interventions that have occurred over time including the construction of dams higher in the catchment, the development of urban centres, licensed river extractions and changing catchment conditions.
River flow regimes can be characterised by the size and duration of various flow levels. How often a flow of a particular size is likely to occur is best illustrated by a Flow Duration Curve (FDC). A flow duration curve plots the volume of flow (megalitres per day) against the percentage of days that such a flow will be equalled or exceeded.
This river flow data developed for the pipeline environmental assessment is presented as a flow duration curve in Figure 11. This flow data represents recent catchment and current development and represents the likely future water availability should the catchment conditions in the future prove to be similar to that of the last ten years (Geolyse, 2012). The recent catchment conditions generate less runoff and streamflow compared to historical conditions.
Figure 11 also shows the following three flow classes as defined by the Government of NSW (2002): • Class A (low flows): generally from the 80th to the 95th percentile flow (cease to pump); • Class B (low to moderate flows): generally from the 50th to the 80th percentile flow; and • Class C (moderate to high flows, freshes and floods): generally from 0 to the 50th percentile flow.
The cease to pump threshold establishes the river flow at which it is recommended that licensed pumping must stop. The 95th percentile flow is recommended as this protects the very low flows and the supply to basic right pumpers during dry periods (Government of New South Wales, 2002).
The revised Macquarie catchment modelling indicates there is more water resource in the Macquarie River system than original understood during the initial investigation and planning phases of the Macquarie River to Orange pipeline project. The reliability of the resource is confirmed through upstream streamflow data that indicates there is some flow in the Macquarie River at least 99% of the time and in the Turon River at least 91% of the time.
Under the assumptions of a catchment that generates less runoff than it has in the past, due to catchment interventions and catchment management actions that lead to reduced runoff, the modelling demonstrates: • there is a substantial volume of water in the Macquarie River at the proposed offtake point, with the average annual volume exceeding 300,000 ML/year; and • flows greater than the proposed extraction level of 34 ML/day are expected to occur for at least 73% of the time which provides adequate pumping opportunity.
Based on the revised modelling it was concluded that the Macquarie River provides a viable water source that could contribute to the water security for Orange (Geolyse, 2012).
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1000000
100000
CLASS C CLASS B CLASS A Moderate to high flows, Low to moderate Low Flows freshes and floods flows 10000
1000 ML/day
100 95th flow percentile cease to pump cease percentile flow 95th
10
1 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Percent of time flow is exceeded
Figure 11: Modelled Macquarie River flow duration curve (Geolyse, 2012)
3.2.6.4 Potential Water Supply
The current system assessment is based on pumping 12 ML/day from the river when the river flow is greater than 34 ML/day and the level in Suma Park Reservoir less than 90% (referred to as the 12/34 rule).
Under this operating rule, the transfer of water from the Macquarie River increases the Orange water system secure yield by 2,800 ML/year.
Model results show (Geolyse, 2012): • pumping occurs approximately 38% of the time, averaging 139 pump days per year, ranging from zero to 323; • of the 118 years modelled some transfer would have occurred in 116 of the years; • the average long term extraction from the river is 0.54% of the annual flow, ranging from zero to 6.5% for individual years; • the maximum extraction from the river in any one day is 35% (i.e. 12 ML/day extracted during a river flow of 34 ML/day); • the average extraction on pumping days is 1.7% of flows in the river; and • the average annual extraction is approximately 1,665 ML/year, ranging from zero to 3,876 ML/year.
Figure 12 shows the FDC for the 12/34 rule upstream and downstream of the extraction point. The difference between the two lines represented the volume removed.
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Scenario B With Project
1000000
100000
10000
1000 ML/day
100
10
1 0 10 20 30 40 50 60 70 80 90 100 Percent of time flow is exceeded
Figure 12: FDC impact for 12/34 rule
3.2.6.5 The 2000 to 2010 Drought
This section presents an assessment of how Orange City Council’s combined water storage could have behaved if the project was in operation through the period from January 2000 to December 2010.
How was the Assessment Undertaken? • Daily Macquarie River flow data was obtained from the Scenario B flow series (Geolyse, 2012) at the proposed offtake point for the period covering January 2000 to December 2010. • The potential volume available from the Macquarie River was determined based on the 12/34 operating rule i.e. extracting 12 ML/day from the river whenever the flow is greater than 34 ML/day. The daily extraction was summed to provide a potential monthly transfer value; • A monthly water balance was developed for Suma Park Reservoir. This was developed using the actual end of month storage data and monthly water consumption. The average monthly storage volume was used to determine a surface area so that evaporation losses and direct rainfall additions to the storage could be calculated. Using this data, a monthly inflow series was determined using a back calculation method; • Monthly water consumption data was analysed to determine how each level of water restriction applied over the period impacted on the amount of water consumed. This was done so that the potential higher water consumption could be accounted for with the Macquarie River pipeline option as storages would not fall to the historic levels; and • A second monthly water balance model was established for Suma Park Reservoir that used the inflow series derived from the actual data and added the transfer of water from the Macquarie River whenever the volume in Suma Park Reservoir was less than 90%. The following calculations were undertaken for each month of the model: – the storage at the start of the month was checked to see if it was less than 90%. If it was the volume available from the Macquarie River was transferred to Suma Park Reservoir.
PAGE 35 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
– the combined storage at the start of the month was used to define the level of water restriction that would be in place and the corresponding monthly water demand applied. If this monthly demand was less than the actual monthly demand, the actual monthly demand value was used. – the storage in Suma Park Reservoir at the start of the month was used to determine the surface area to calculate evaporation losses and direct rainfall additions. – the actual Spring Creek Reservoir storage was added to the calculated Suma Park Reservoir storage to determine the combined storage volume at the end of each month, as the combined storage volume is used to determine the water restriction level.
Macquarie River Flow Data
Monthly Macquarie River flow data used in the assessment is shown in Figure 13. The daily data used to derive these monthly flow volumes show that the flow in the river was greater than 34 ML/day for 2,873 days of the 4,018 days used in the assessment (72% of days).
100000
90000
80000
70000
60000
50000 Flow, ML/month Flow, 40000
30000
20000
10000
0 Jul-00 Jul-01 Jul-02 Jul-03 Jul-04 Jul-05 Jul-06 Jul-07 Jul-08 Jul-09 Jul-10 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09 Jan-10 Oct-00 Oct-01 Oct-02 Oct-03 Oct-04 Oct-05 Oct-06 Oct-07 Oct-08 Oct-09 Oct-10 Apr-00 Apr-01 Apr-02 Apr-03 Apr-04 Apr-05 Apr-06 Apr-07 Apr-08 Apr-09 Apr-10 Figure 13: Monthly Macquarie River flow data (Scenario B) – January 2000 to December 2010
Combined Storage
Figure 14 shows the actual combined storage and the modelled combined storage with the addition of inflows from the Macquarie River. This shows that with the addition of the Macquarie pipeline transfer, the combined storage level would not have fallen much below 60% and water restrictions would have remained at Level 2 or less.
PAGE 36 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Actual With Macquarie River pipeline operating Transfer Pump Operation
100%
90%
80%
70%
60%
50%
40%
30% Combined Storage (Suma Park and Spring Creek) Spring and Park (Suma Storage Combined
20%
10%
0% Jul-00 Jul-05 Jul-06 Jul-01 Jul-02 Jul-03 Jul-04 Jul-07 Jul-08 Jul-09 Jul-10 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09 Jan-10 Oct-04 Oct-05 Oct-10 Oct-00 Oct-01 Oct-02 Oct-03 Oct-06 Oct-07 Oct-08 Oct-09 Apr-00 Apr-01 Apr-02 Apr-03 Apr-04 Apr-05 Apr-06 Apr-07 Apr-08 Apr-09 Apr-10 Figure 14: Combined storage behaviour: 2000 to 2010 analysis
Table 3.6 summarises the actual water consumption and the modelled water consumption that could have been supplied if the Macquarie River to Orange pipeline was operating. This demonstrates that increased annual water consumption could have been provided as the level and period of water restrictions would have been less with the addition of water from the Macquarie River.
Table 3.6 – Comparison of actual and modelled annual water consumption – 2000 to 2010 analysis
Actual Consumption Modelled Consumption Change Year ML ML ML 2000 6326 6367 + 40
2001 7063 7063 0
2002 7124 7124 0
2003 5239 5604 + 365
2004 4973 5525 + 553
2005 5138 5680 + 542
2006 5941 6095 + 154
2007 4896 5353 + 456
2008 4389 5238 + 849
2009 4091 5348 + 1257
2010 3765 5254 + 1490
PAGE 37 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Table 3.7 shows the modelled annual river flow and volume extracted for each year of the assessment. This shows that the annual extractions ranged from 0.6% to 3.9% of the river flow, with an average of 1.5% over the period.
Table 3.7 – River flow and extraction – 2000 to 2010 analysis
Annual Macquarie River Volume Extracted as Annual Extraction Year Flow Percentage of Annual ML ML River Flow 2000 372790 0 0.0%
2001 142371 2208 1.6%
2002 66370 1668 2.5%
2003 173228 3144 1.8%
2004 145844 1884 1.3%
2005 285224 1752 0.6%
2006 109407 2028 1.9%
2007 180889 4200 2.3%
2008 162491 3972 2.4%
2009 68031 2628 3.9%
2010 68658 2544 3.7%
Totals 1775303 26028 1.5%
3.2.6.6 Estimated Capital and Operating Costs
The estimated capital cost of the transfer system (pump stations, balance tanks, pipelines, access roads and controls) is $47.0 million. This cost includes upgrading power supply in the area to meet the demand and all design and approvals.
Council was successful in obtaining $38.2 million of Federal and State government funding for the pipeline project in March 2011. Therefore Council’s contribution to the project is $8.8 million.
Average annual operating costs for the project are estimated as $736,801 a breakdown of which is shown in Table 3.8.
Table 3.8 – Macquarie pipeline average annual operating costs
Item Average Annual Cost
Labour $25,000
Radio communications $10,000
Monitoring and reporting $50,000
Road and fence maintenance and weed control $50,000
Equipment servicing $15,000
Capital replacement $100,000
Power $486,801
Total $736,801
PAGE 38 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
The largest component of the annual operating cost is power which is based on the long term average annual transfer of 1,665 ML/year.
The electricity tariff structure was provided by Essential Energy and is made up of three components: • Meter charges - $500 per month for each meter, of which there will be three at the three pump station locations. As such, the minimum annual charges will be $18,000 if no pumping occurs; • Demand charges – these are monthly charges that apply if power is drawn in a month. These charges vary depending on the total kilowatts and time of day (i.e. peak, shoulder or off-peak). The demand charges for shoulder are $18,176.10 per month and $4,931.50 for the off-peak periods, a total of $23,107.60 per month. If the system operates in any one month these charges apply whether it runs for one day or the full month; and • Consumption charges – these are unit charges with the tariff depending on the time of day or week (i.e. peak, shoulder, off-peak or weekend).
The transfer system has been sized to transfer 12 ML/day over 19 hours. This means that the pumps would be set to only operate in shoulder, off-peak and weekend time periods. This avoids the high cost associated with the demand charges and unit charges for peak periods.
Results from the water balance modelling were summed to provide monthly pumping volumes which were converted to pump run time in hours. The tariffs described above were then calculated to provide monthly and annual power costs. The average annual power cost from this analysis is $486,801.
3.2.6.7 Summary
Table 3.9 summarises the option of using transfer from the Macquarie River as part of the water supply system.
Table 3.9 – Summary of Option SW3: Macquarie River to Orange pipeline
Measure Result
Capital cost, $ $47,000,000 ($8,800,000 with Govt. grant)
Operating cost, $/year $736,801
NPV – capital cost, ($2010) $40,411,000 ($7,566,000 with Govt. Grant)
NPV – operating cost, ($2010) $8,811,000
Potential increase in secure yield, ML/year 2,800
Capital costs, $/ML increase in secure yield $977 ($183 with Govt. Grant)
Operating costs, $/ML increase in secure yield $213
Total cost of secure yield supplied, $/ML increase in secure yield $1,190 ($396 with Govt. grant)
Change in TRB if adopted $151 per assessment ($50 per assessment with Govt. grant)
Greenhouse Gas Emissions (operating power only) 2.18 tonnes CO2e/ML
Issues to consider • Macquarie River hydrology • Operation to prevent significant impact • Approval process • Water quality risk assessment
Likely timeframe to complete 2 to 3 years
PAGE 39 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
3.2.7 BURRENDONG DAM TO ORANGE PIPELINE 3.2.7.1 Background
Burrendong Dam is situated on the Macquarie River, just below its junction with the Cudgegong River about 30 km upstream from Wellington. The dam creates a storage with a capacity of 1,188,000 ML and provides water for town water supplies, river flows and domestic requirements, irrigated agriculture, industry, flood mitigation, environmental flows and recreation (http://www.statewater.com.au/_Documents/Dam%20brochures/Burrendong%20Dam%20brochure.pdf).
The option of providing a pipeline from Burrendong Dam to Orange was considered in the Centroc Water Security Study (MWH, 2009). It was excluded from the short listed options in the regional study as it was considered to be not feasible and better alternatives were available (namely supplying water from the Lachlan system). One reason for this was the elevation of the dam.
3.2.7.2 Conceptual System
A pipeline from Burrendong Dam is a technically straight forward water supply option. Conceptually it would require: • a pump station located downstream of the dam (see below); • a pipeline to connect the pump station to Suma Park Dam (approximately 78 km); and • booster pump stations and balance tanks along the pipeline route.
The offtake point would need to be located on the downstream side of the dam to ensure that water could be extracted at all times (subject to licence conditions). If the extraction point was upstream of the dam wall (say at Mookerawa) there may be times when water could not be obtained due to low dam levels.
As Burrendong Dam forms part of the regulated supply in the Macquarie River system, an access licence would be required to extract water for town water supply. If this option was pursued, it would be preferable to obtain a high security licence rather than a general security licence that would be subject to allocation limitations. A high security allocation would need to be purchased on the open market. It is estimated that this could cost around $3,000 per ML.
A conceptual pipeline route connecting the Burrendong Dam to Suma Park Dam is shown in Figure 15. This route was selected to follow road and rail easements as much as possible. A conceptual transfer system was sized for a peak flow of 12.3 ML/day (4,500 ML/year). This system would require 450 mm diameter DICL and 500 mm polyethylene pipeline and four pump stations with a total power demand of 1,657 kW.
A pipeline from Burrendong Dam has significant capital costs. It is reasonable to suggest that if this option was used, sufficient licence allocation would be required to allow this system to provide a secure yield increase similar to the proposed Macquarie River to Orange pipeline project (2,800 ML/year). It was further assumed that the Burrendong pipeline option could attract the same State Government grant ($18.2 million) as the Macquarie River pipeline project.
Modelling determined that a 12.3 ML/day system transferring water whenever Suma Park Reservoir was less than 70% could provide an additional 2,800 ML/year secure yield for Orange. The system was used in 82 years of the 118 years modelled. The long term average transfer for this system was 1,260 ML/year.
PAGE 40 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Figure 15: Conceptual pipeline route from Burrendong Dam to Orange
3.2.7.3 Preliminary Capital and Operating Costs
Preliminary capital cost estimates for the system are provided in Table 3.10.
Table 3.10 – Burrendong Dam pipeline – preliminary cost estimates
Item Cost ($M)
High security licence (3,300 ML) $9.90
Transfer system $69.45
Approvals $2.50
Survey, investigation, design and project management (15%) $10.42
Contingency (15%) $10.42
Total $102.69
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Annual operating costs based on an average annual transfer of 1,260 ML/year are $734,391/year as follows: • Power $384,391/year • Maintenance $350,000/year
The annual power cost was estimated using the same methodology as the Macquarie River to Orange pipeline option.
3.2.7.4 Summary
Table 3.11 summarises the option of using transfer from Burrendong Dam as part of the water supply system.
Table 3.11 – Summary of Option SW4: Burrendong Dam to Orange pipeline
Measure Result
Capital cost, $ $102,686,000 ($84,486,000 with State Govt. grant)
Operating cost, $/year $734,391
NPV – capital cost, ($2010) $76,290,000 ($62,405,000 with State Govt. grant)
NPV – operating cost, ($2010) $7,099,000
Potential increase in secure yield, ML/year 2,800
Capital costs, $/ML increase in secure yield $1,845 ($1,509 with State Govt. grant)
Operating costs, $/ML increase in secure yield $172
Total cost of secure yield supplied, $/ML increase in secure yield $2,017 ($1,681 with State Govt. grant)
Change in TRB if adopted $256 per assessment ($213 with State Govt. grant)
Greenhouse Gas Emissions (operating power only) 2.50 tonnes CO2e/ML
Issues to consider • Need to obtain high security licence • Potential regional solution (Macquarie/Lachlan connection) • Approval process • Land ownership along pipeline route • Regional water network
Likely timeframe to complete 4 to 6 years
3.2.8 MULYAN CREEK DAM 3.2.8.1 Introduction
The option of a new water supply storage on Mulyan Creek west of Clergate was identified by a local resident. Conceptually, water captured by the storage would be transferred back to Suma Park Reservoir to supplement the Orange water supply.
This option was assessed by: • calculating the reservoir storage size required to satisfy certain demands; and • estimating the capital and operating costs associated with the construction of a dam and infrastructure to return water to Suma Park Dam.
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3.2.8.2 Catchment Description
The proposed site of the dam is located on Mulyan Creek approximately 3.5 km west of Clergate. At this location Mulyan Creek passes through a steep valley as it falls from a height of around 820 mAHD down to 700 mAHD. The Mulyan Creek catchment rises in forested hills north of the village of Mullion Creek. The creek runs in a southerly direction towards Clergate and then turns to the west, dropping off the tablelands to join the Bell River.
The Mulyan Creek catchment and location of the proposed dam are shown on Figure 16. The catchment area to the location of the proposed dam is approximately 38 km². The catchment is predominately open grazing land with some forest areas along the catchment watershed.
3.2.8.3 Storage Capacity Required to Meet Demand
The storage capacity required to satisfy certain demands was assessed using a mass curve analysis. Catchment modelling was used to generate a monthly stream flow data set for the period 1890 to 2007 using catchment parameters derived for the Ploughman's Creek stormwater harvesting scheme assessment, which included generation of stream flows for the Bell River (Geolyse, 2009b).
The inflow data are added cumulatively and plotted as a mass curve, as shown in Figure 17. This curve has an undulating shape; the steep parts representing periods of high flow, and the flatter parts periods of low flow. Times of zero flow would correspond to horizontal portions of the curve. The Federation Drought period is indicated as a long relatively flat part of the mass curve.
Construction of a new dam is likely to be subject to environmental flow requirements. It was assumed that these would be along the lines of the 80/20 rule. In this scenario, the new dam is fully transparent to all flows up to the 80th percentile flow, i.e. all inflows below the 80th percentile entering the dam will be passed through the dam. The dam is also 20% translucent for flows above the 80th percentile i.e. for all flows above the 80th percentile flow, 20% of the difference between the 80th percentile flow and the actual flow plus the 80th percentile flow is released. The mass curve represented by the red line in Figure 17 shows the cumulative net inflow available for a storage dam after allowing for the release of environmental flow based on the 80/20 rule.
A constant rate of demand on a mass curve would appear as a straight line. To be feasible, this would need to have a flatter slope than the average flow rate line. The average slope of the cumulative mass curve equates to an annual demand of about 2,520 ML/year. Therefore, the potential annual demand supplied by a dam on Mulyan Creek would need to be less than this amount.
The smallest reservoir size required to supply a given constant demand over the period of flow data can be found by drawing straight lines parallel to the demand line starting from the peaks of the mass curve. When demand lines are projected over the troughs to the right of each peak (periods when the inflow is low), the greatest vertical distance between the demand line and the mass curve in each trough will represent the storage required to maintain supply during this period of low flow. Over the whole period, the storage needed to maintain full demand will be the greatest of the values for the individual low flow periods.
PAGE 43 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Figure 16: Conceptual Mulyan Creek Dam, catchment
The mass curve analysis was used to generate a relationship between the storage volumes required to meet a given annual demand. This relationship is shown on Figure 18. The relationship includes the 80/20 environmental flow rule. No allowance was made for other losses such as evaporation and seepage, or direct rainfall additions to the storage water surface.
The storage-demand relationship (Figure 18) shows that reservoir storage of about 1,640 ML is required to supply an annual demand of 500 ML/year. A storage volume of 16,100 ML is required to supply an annual demand of 2,000 ML/year.
PAGE 44 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Catchment inflow Net inflow after 80/20 environmental flow
450000
400000
350000
300000
250000
200000 Cumulative Flow, ML
150000
100000
50000
Federation Drought Period 0
1890 1892 1894 1896 1899 1901 1903 1905 1908 1910 1912 1914 1917 1919 1921 1923 1926 1928 1930 1932 1935 1937 1939 1941 1944 1946 1948 1950 1953 1955 1957 1959 1962 1964 1966 1968 1971 1973 1975 1977 1980 1982 1984 1986 1989 1991 1993 1995 1998 2000 2002 2004 2007 Figure 17: Mulyan Creek mass curve of inflow to proposed dam
18000
16000
14000
12000
10000
Volume, ML Volume, 8000
6000
4000
2000
0 0 200 400 600 800 1000 1200 1400 1600 1800 Demand, ML/year
Figure 18: Mulyan Creek Dam storage-demand relationship
PAGE 45 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
3.2.8.4 Conceptual Storage Capacity
A conceptual stage-storage curve was generated using 10 m contours from the Ophir 1:25,000 topographic map (8731-4-S). A conceptual dam embankment was located just at the point where Mulyan Creek enters the narrow valley. The conceptual dam and approximate extent of the storage at a full supply level of 820 m AHD is shown on Figure 19.
The stage, storage and surface area data derived for the analysis is listed in Table 3.12. This data shows an approximate full supply capacity of 1,350 ML with a surface area of around 22 ha.
Table 3.12 – Conceptual Mulyan Creek Dam Stage-Storage-Surface Area Data
RL Surface Area Volume mAHD ha ML
800 0.02 0
810 2.33 118
820 22.32 1,350
Figure 19: Conceptual Mulyan Creek Dam
3.2.8.5 Potential Demand Supplied
Using the storage-demand relationship reflected in Figure 18 coupled with the conceptual storage volume of 1,350 ML indicates that a dam on Mulyan Creek could supply an average annual demand of 430 ML/year through the worst drought on record. This is shown in Figure 20.
Figure 21 shows how this average annual demand could be supplied through the Federation Drought period.
PAGE 46 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
5000
4500
4000
3500
3000
2500 Volume, ML Volume,
2000
1500 Conceptual Maximum Dam Volume 1,350 ML
1000
Annual Demand Supplied = 430 ML/year 500
0 0 100 200 300 400 500 600 700 800 900 1000 Demand, ML/year
Figure 20: Potential annual demand supplied by 1,350 ML Mulyan Creek Dam
Cumulative Demand Dry Period Cumulative Net Inflow Cumulative Demand - 430 ML/year
25000
20000 Maximum Storage required = 1350 ML
15000 ML
10000
5000
0 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901
Figure 21: Conceptual demand supplied through Federation Drought period for Mulyan Creek Dam
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The potential supply derived using this method is not the same as a secure yield value. It is the annual demand that could be supplied through the worst drought on record. Secure yield is the annual demand that could be supplied through the worst drought on record, with the storage already starting from a drawn down condition. The secure yield criteria can be viewed as satisfying about a 1 in 1,000 year drought. Therefore the secure yield that could be provided from the conceptual Mulyan Creek dam system would be less than 430 ML/year; however this value was adopted as the annual supply from the dam for the purpose of this assessment.
3.2.8.6 Transfer System
A conceptual pipeline alignment is shown in Figure 16. This alignment follows road reserves and the railway corridor as much as possible. The pipeline has a length of approximately 16 km and rises from 780 mAHD (the assumed level of a pump station downstream of the dam) to a maximum elevation of 890 mAHD, before dropping back down to 842 mAHD (the approximate elevation of Suma Park Reservoir FSL).
The preliminary design pipe sizes and hydraulic grade line for a design flow rate of 3 ML/day are shown in Figure 22. It was considered that the pipeline should be sized to take about two times the average daily flow. The preliminary hydraulic analysis for a 3 ML/day transfer system is based on: • 280mm HDPE pipe; and • One pump station at the base of the proposed dam with a total power requirement of 85 kW.
NS HGL 950
900
850 RL mAHD
800
85kW Pump Station
750 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000 16,000 Chainage (m)
Figure 22: Preliminary hydraulic grade line and pipe sizes
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3.2.8.7 Preliminary Cost Estimates
Preliminary capital cost estimates for the system are provided in Table 3.13.
Table 3.13 – Mulyan Creek Dam – preliminary cost estimates
Item Cost ($M)
Land $0.80
Dam $19.69
Transfer system $11.75
Approvals $1.50
Survey, investigation, design and project management (15%) $4.72
Contingency (15%) $4.72
Total $43.18
Annual operating costs based on an average annual transfer of 430 ML/year are $230,000/year as follows: • Power $130,000/year • Maintenance $100,000/year
3.2.8.8 Summary Table 3.14 summarises the option of using Mulyan Creek dam as part of the water supply system.
Table 3.14 – Summary of Option SW5: Mulyan Creek Dam
Measure Result
Capital cost, $ $43,163,000
Operating cost, $/year $151,000
NPV – capital cost, ($2010) $33,915,000
NPV – operating cost, ($2010) $1,567,000
Potential increase in secure yield, ML/year 430
Capital costs, $/ML increase in secure yield $5,341
Operating costs, $/ML increase in secure yield $247
Total cost of secure yield supplied, $/ML increase in secure yield $5,588
Change in TRB if adopted $109 per assessment
Greenhouse Gas Emissions (operating power only) 0.52 tonnes CO2e/ML
Issues to consider • Environmental approvals • Land ownership • Low yield
Likely timeframe to complete 5 to 8 years
PAGE 49 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
3.2.9 CADIA VALLEY OPERATIONS WATER INFRASTRUCTURE
Cadia Valley Operations has significant water supply infrastructure that supports its mining and processing operations. This includes: • Cadiangullong Dam which has a capacity of 4,200 ML and catchment area of 38 km2. This dam also receives flows diverted from a small weir on nearby Cadia Creek (Gilbert & Associates, 2009); • Rodds Creek Dam which has a capacity of 14,500 ML. This dam has very limited catchment and is used to store water pumped from the Belubula River (under licence); • A general security water licence in the Belubula system for 4,080 ML/year; and • Unregulated licences totalling 7,325 ML/year.
The importance of the water supply infrastructure to the region was identified in the 1996 agreement. Clause 2.4 of the Cadia Project Water Supply Agreement states:
the Company recognises that the water infrastructure on the Cadia site is significant to the longterm development of the region and agrees that when the Company, its successors or assigns have no further use for the water resources or the water infrastructure at the Site, the Company shall negotiate in good faith toward making the infrastructure available for the public benefit of the region, which negotiations shall be between the Company and the Council and subject to the due process of the relevant water authority of the day.
The future importance of this infrastructure was also captured in the 2009 Strategic Water Supply Strategy which included the following actions as part of management, promotion and lobbying:
(d) Acknowledge longer-term options such as the acquisition of water infrastructure and entitlements upon the wind up of operations at the Cadia Valley Operations (CVO) site, including Cadiangullong Dam, Rodds Creek Dam, groundwater, surface water and associated pipelines and pumping stations;
(e) Include the concept of first option for acquisition of water infrastructure and entitlements at the Cadia site within the current Effluent Agreement negotiations with CVO;
The water supply agreement is currently under negotiation due to the continued and expanding mining operations. It is intended that the above clause will remain in the revised agreement.
It is understood that the recently approved Cadia East project is expected to extend the mining operations until at least 2030. The site water infrastructure is therefore a longer term water security option.
3.2.10 MANAGING STORAGE EVAPORATION
Water balance modelling indicates that the average annual net evaporation loss from the three water storages is 1,157 ML/year (refer to Table 3.15).
Table 3.15 – Average storage evaporation loss
Storage Net Evaporation Loss, Proportion of long term ML/year average storage volume, %
Gosling Creek Reservoir 70 14%
Spring Creek Reservoir 384 9%
Suma Park Reservoir 703 5%
Total 1,157
PAGE 50 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Water can be saved by reducing evaporation losses. Engineered systems available include: • chemical based systems dispersed on the water surface that restrict the water-surface boundary layer; • systems that limit solar energy input including fixed or floating covers; and • floating modular units.
Reservoir management can also be used to reduce evaporation losses by using water from inefficient dams therefore leaving water in more efficient dams. In terms of the two major storages in the Orange water supply system there is not a lot of difference in their evaporation efficiency and only minor gains would be made by managing these storages differently.
The use of chemical based systems (monolayers) was not considered due to the large surface areas and the fact that the storages are subjected to substantial wind action that would break up any surface product. They also have a low evaporation reduction potential varying from 0% to 40% (Watts, 2005).
Likewise, the large surface areas would preclude the use of floating covers due to excessive capital costs.
A proposal was put forward to Council based on the use of floating modular units that support solar panels (Hydrosun system). The proposal presented to Council was estimated to cost $150 million and had the potential to produce 125,000 MWhr of electricity per year.
The net evaporation loss through the critical drought period is around 1,000 ML/year. Assuming a floating cover system could reduce this by around 80% would equate to an estimated secure yield of around 800 ML/year for this system.
Adopting approval, engineering, contingency and capital costs of around $195 million and annual maintenance costs of $50,000/year, this equates to $14,494 per ML increase in secure yield (excluding income from electricity generation). An average income from electricity generation of around $0.16/kWhr would be required to make the system cost neutral over 20 years (assumed life of floating modules).
While this system is technically feasible and could possibly result in income generation due to electricity production, it has very high up front capital costs and in terms of the potential secure yield benefit, better options are available. The NSW Office of Water also expressed concern with regards to the potential for the floating modules to impact on the dam integrity during times of flood. For these reason, this system was not considered further.
3.2.11 LONG LIST RECOMMENDATIONS
The following long list of potential surface water options can be derived from the above assessment: • SW1: raising Suma Park Dam by 1.0 m (included in BAU); • SW2: Lake Canobolas; • SW3: Macquarie River to Orange pipeline (included in BAU); • SW4: Burrendong Dam to Orange pipeline; • SW5: Mulyan Creek Dam; • SW6: Cadia Valley Operations water infrastructure; • SW7: managing evaporation from storages; and • SW8: de-silting Spring Creek Dam.
Further consideration and short listing of options is presented in Section 4.
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3.3 STORMWATER
3.3.1 EXISTING STORMWATER HARVESTING SCHEMES
Orange City Council implemented ground-breaking stormwater harvesting schemes in 2009 and 2010. These are located on Blackmans Swamp Creek and Ploughmans Creek (refer to Figure 23). The objective of the stormwater harvesting schemes is to augment the city’s potable water supply in a manner that protects both public health and the downstream environment. This is achieved by: • harvesting a portion of high flows from the creek; • having adequate risk management systems in place to meet water quality objectives; and • adaptively managing the scheme so that its impact is not significant and that the needs of downstream users and the aquatic environment are not compromised.
The schemes make use of the additional runoff generated by development in the catchment. The basic concept involves capturing a portion of the high flows in the creeks during storm events, then treating and transferring these into Suma Park Reservoir to augment the city’s bulk water supply.
Figure 23: Stormwater harvesting infrastructure
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3.3.1.1 Existing Schemes Approval Status
Orange City Council has two stormwater harvesting schemes: the Blackmans Swamp Creek Stormwater Harvesting Scheme (BSCSHS); and the Ploughmans Creek Stormwater Harvesting Scheme (PCSHS). The following section provides a summary of the approval status for each scheme.
Blackmans Swamp Creek Stormwater Harvesting Scheme
Council approved the BSCSHS under Part 5 of the Environmental Planning and Assessment Act 1979 in October 2008. The NSW Office of Water issued Emergency Authorisation (EA) under Section 22A of the Water Act 1912 in August 2008 which allowed the construction and operation of specific components of the scheme, subject to conditions. These scheme components include: • The harvesting weir on Blackmans Swamp Creek; • The main pump station and pumps (Pump Station 1 adjacent to Blackmans Swamp Creek just upstream of the harvesting weir); and • A 230 ML holding pond constructed on an unnamed tributary to Blackmans Swamp Creek.
The original EA lasted for 12 months (to August 2009) and was extended by six months (to February 2010) and then a further six months to August 2010.
The EA only applies for an emergency period. The end of the emergency period, as nominated by Council, is when the storage in Suma Park Reservoir goes above 50%.
The water storage reached 50% in early August 2010 following good late winter rainfall and reached 100% in late August 2010. As a result, the EA is no longer active for the scheme and it cannot be used to harvest stormwater unless the volume in Suma Park Reservoir falls below 50% and a new EA is issued by the NSW Office of Water.
Orange City Council made application under Section 10 of the Water Act 1912 for a licence to use the BSCSHS on a permanent basis. This would allow stormwater harvesting at all times when Suma Park Reservoir is less than 100%, subject to the scheme’s operating rules and any licence conditions. The BSCSHS would be licensed under two separate licences: one for the harvest weir and pumps located on Blackmans Swamp Creek; and one for the 230 ML holding pond and pumps located on an unnamed drainage line that is a tributary to Blackmans Swamp creek.
Objections were raised to the permanent licence application and these objections are currently the subject of a Local Land Board (LLB) hearing. The matter before the LLB relates to both licences. The BSCSHS therefore cannot be used while Suma Park Reservoir is above 50% until the licence application is determined.
Ploughmans Creek Stormwater Harvesting Scheme
The PCSHS obtained consent under Part 5 of the Environmental Planning & Assessment Act 1979 in January 2010. An EA for the scheme was granted under Section 22A of the Water Act 1912 in early 2010. The EA included the same condition in that it only applied for the emergency period which ended in August 2010.
A licence was granted under Section 10 of the Water Act 1912 (Licence 80SL96331) for the permanent operation of the scheme in August 2011. The scheme operation is subject to operating rules attached to the licence (described in Section 3.3.1.3).
The PCSHS transfers harvested stormwater to the 230 ML holding pond which acts as a balancing point before the stormwater is treated. As the holding pond licence has not been granted (see above), it cannot currently be used for this purpose. Therefore, the PCSHS can only be used if the harvested water is delivered directly to the batch ponds, rather than the 230 ML holding pond.
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Council is investigating the feasibility of a pipe to bypass the holding pond so that harvested stormwater is transferred directly to the batch ponds. This would allow operation of the PCSHS independent of the holding pond. However it reduces the schemes operational flexibility and removes one component of the treatment train for the harvested stormwater. This latter issue is being considered through a risk assessment process.
Therefore, the PCSHS is licenced to harvest stormwater whenever Suma Park Reservoir is less than 100% however it cannot be used until either: • The licence for the 230 ML holding pond is granted; or • A bypass system is developed to isolate the holding pond.
Summary
The current approved stormwater harvesting schemes are: • Blackmans Swamp Creek stormwater harvesting operating on a 50% Suma Park Reservoir trigger – this is referred to as Blackmans Swamp Creek Stage 1a; and • Ploughmans Creek stormwater harvesting operating on a 100% Suma Park Reservoir trigger.
3.3.1.2 Blackmans Swamp Creek Stormwater Harvesting
Description
The urban area of Orange lies within two local creek catchments, the largest of which is Blackmans Swamp Creek, covering about 34 km² to its junction with Summer Hill Creek. Blackmans Swamp Creek rises in rural land south of the city and flows through the central business district, heading in a north-easterly direction, passing immediately west of Suma Park Dam before joining with Summer Hill Creek a kilometre downstream of the dam. Approximately 70% of the city falls within this catchment (refer to Figure 24). The catchment area of Blackmans Swamp Creek upstream of the harvesting point is 30.5 km2. The stormwater harvesting scheme 230 ML holding pond, which is on an unnamed tributary to Blackmans Swamp Creek, has a further catchment area of 2.5 km2.
Layout and Operation
The layout of the harvesting scheme is illustrated in Figure 25. Major components and how they operate are described below: • Two large Gross Pollutant Traps (GPTs); one located on Blackmans Swamp Creek at Dalton Street and the other on a major piped drainage line near Margaret Stevenson Park. These are designed to remove a portion of the larger pollutants from the runoff. • A rock and gabion harvesting weir located on Blackmans Swamp Creek just upstream of the city’s Sewage Treatment Plant. This weir has a capacity of approximately 3 ML at its spillway level. Its role is to create a weir pool during runoff events from which stormwater can be harvested. The weir includes an unrestricted 300 mm pipe to allow low flows to pass through. • Pump Station 1 which is located immediately upstream of the harvesting weir. This pump station has three variable speed pumps, each with a capacity of 225 L/s. A maximum of two pumps are used with the role of the two duty pumps being rotated between the three pumps (combined harvest rate of 450 L/s). • A 230 ML holding pond that is used to balance harvested stormwater flows with the treatment system. This holding pond is constructed across an unnamed watercourse that is a tributary to Blackmans Swamp Creek. The catchment above the holding pond is about 251 ha and includes developed industrial areas and open rural zoned land. • Pump Station 2 which extracts water from the holding pond and transfers it to the batch ponds. This pump station has a capacity of 150 L/s. • A treatment shed that includes flocculant storage and a dosage point. A flocculant (aluminium chlorohydrate) is added to the harvested stormwater as it moves from the holding pond to the batch ponds to promote settling of suspended particles and attached contaminants.
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• Two 17 ML batch ponds which are used in parallel and provide residence time for the treated water to settle. • Pump Station 3 with a capacity of 150 L/s to transfer treated stormwater to Suma Park Dam. The treated stormwater is transferred through an existing main towards Suma Park Dam, with an extension allowing discharge to the dam.
Figure 24: Stormwater harvesting catchments
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Figure 25: BSCSHS Stage 1 scheme layout
Operating Rules
The BSCSHS originally had nine operating rules. This was reduced to seven rules (three deleted and one added) during negotiations with NOW when assessing the licence application. Operating rule 10 is also being reviewed under current licence negotiations and the final water allocation for environmental flow is not finalised. The current operating rules for the BSCSHS are listed in Table 3.16.
Initial Operation
The scheme was commissioned in March 2009, with the first harvest event occurring on 4 April 2009. The first harvested water was transferred to Suma Park Dam on 21 April 2009 following testing and verification that scheme water quality targets had been met.
Initial operational data from the scheme was used to refine long term modelling of how the scheme would perform. This revised modelling reduced the predicted average harvest for Stage 1 from 1,300 ML/year to around 800 ML/year. Modelling will be continually reviewed as more data become available.
During the first 12 months of the scheme operation, there were 46 harvesting events. The total volume harvested over this time was 582 ML which is equivalent to approximately 11% of the city’s current estimated unrestricted annual water demand.
The scheme stopped operating in August 2010 when Suma Park Reservoir rose above 50% storage capacity.
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Table 3.16 – BSCSHS Operating Rules Number Operating Rule 1 Deleted 2 Holding Pond Capacity Stormwater harvesting pumps will not operate if the holding pond is at capacity. 3 Deleted 4 Harvesting Triggers Harvesting will commence when the flow in Blackmans Swamp Creek (pipe and weir flow) reaches 1,000 L/s (as measured at the gauging station located immediately downstream of the harvesting weir) and shut down when the weir pool falls to RL 840.50m or creek flow reduces to 150L/s (as measured at the gauging station located immediately downstream of the harvesting weir). 5 Maintenance of Flow The scheme will be operated to ensure a minimum downstream flow in Blackmans Swamp Creek of 2 ML/day, measured at the gauging station located immediately downstream of the harvesting weir, during the operation of the harvesting pumps. 6 Maintenance of Flow Through Holding Pond Water will be released as required (as determined through consultation with the downstream land owner) from the holding pond to top up the farm dam located below the pond. 7 Deleted 8 Suma Park Dam Storage Stormwater harvesting will be used to supplement the bulk raw water supply when the volume in Suma Park Dam falls below 100% (18,073 ML). 9 Stakeholder Engagement Representation from downstream stakeholders will be included in any review of the Operating Rules. 10 Water for Environmental Flow Runoff from the catchment of the unnamed watercourse draining to the holding pond will be transferred to and banked in Suma Park Dam to provide water for environmental flow releases. The maximum volume held in Suma Park Dam for this purpose shall be 250 ML. This volume shall include the volume of water released under Operating Rule 6.
Staging
The Review of Environmental Factors (REF) for the BSCSHS (Geolyse, 2008a) described that the scheme infrastructure would be constructed in stages with progression to the next stage contingent upon the success of the preceding stage, as confirmed through performance monitoring. The staging was reviewed during the approval process, mainly driven by NOW’s requirement to have a smaller harvest weir. Operational data has led to a further review of the staging. The staging proposed in the REF, how it was altered during the NOW approval process, and the current staging proposal is summarised in Table 3.17.
Further details of the current staging are provided in later sections.
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Table 3.17 – BSCSHS Staging
Stage As described in the REF (1) As revised during NOW Current Staging approval (2)
1 • Upstream GPTs As proposed in the REF with the As revised during NOW approval. • Pump Station 1 addition of a weir structure across • 200 ML holding pond and Blackmans Swamp Creek with un- batch ponds restricted 300 mm diameter pipe. • Treatment systems • Pipelines and controls to The weir has a crest level of RL transfer to Suma Park 842 mAHD and forms a weir pool • Gauging stations of approximately 3 ML when full.
2 Gated weir structure with 40 ML It was proposed that Stage 2 Upstream off-line wetland system weir pool. modifications would include with controlled outlet and installation of a flow control modifications to Pump Station 1 to The larger weir would have a crest mechanism on the 300 mm incorporate a low flow pump. level of RL 844 mAHD. diameter pipe. The ability to reduce the release from the weir during harvesting increases the average system yield.
The gated weir structure was not proposed at this stage. However, it was noted at the time that the construction of the larger gated weir structure was not completely ruled out. The need for the larger structure was to be assessed through analysis of the operational data collected while operating with the revised smaller weir and associated operating rules.
3 Excavation upstream of the weir This remained as a possibility. It • Construction of the gated weir site to increase capacity of the weir was noted that the need for this structure across Blackmans pool. stage would be based on analysis Swamp Creek (as originally of operational data during Stage 1 proposed in REF Stage 2). and 2. As stated in the REF, this • Upgrade to the treatment stage would be subject to further system and transfer system to impact assessment. Suma Park Dam to double is capacity. • New access road to the STP.
Source: (1) Geolyse (2008a); (2) Geolyse (2008b)
3.3.1.3 Ploughmans Creek Stormwater Harvesting
Background
Initial operational data from the BSCSHS highlighted the importance of system storage. Most runoff events have short hydrographs which reduces the time that harvest pumps can operate. If a portion of the runoff hydrograph can be captured, it can then be harvested over a longer period following the runoff event. Otherwise, extremely large capacity pumps are required to extract water as the hydrograph passes downstream.
This effect was modelled and then observed in the BSCSHS. It was recognised that providing storage in the system improves the harvest capability for short runoff events and allows smaller extraction pumps to be used. As a result, constructed stormwater wetlands became an integral component of the Ploughmans Creek Stormwater Harvesting Scheme (PCSHS).
Description
The PCSHS is the second of Orange City Council’s large scale stormwater harvesting projects that form part of Council’s diversified water supply. The scheme obtained approval in January 2010 and construction was completed in mid-2011.
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The PCSHS uses a series of constructed wetlands to capture and treat a portion of the storm flow generated from the catchment. The wetlands are constructed on Ploughmans Creek at Cargo Road and Escort Way, and on unnamed tributaries to Ploughmans Creek at Somerset Park and North Orange Sewage Pump Station (SPS) No. 2 (known in this report as the Brooklands site). The constructed wetlands are shown on Figure 23.
The harvest points capture runoff from a total catchment area of 10.56 km2. It is estimated that with current development, about 228 ha (21.6%) of the catchment is impervious. This is estimated to increase to around 265 ha (25%) with the future development in the Ploughmans Valley and North Orange development areas. The catchment areas are shown on Figure 24.
Each constructed wetland is designed to capture a portion of the storm flow generated during rainfall events which is then released at a slow rate over four to five days following the rainfall. The volume captured in each wetland is (assuming a runoff event in the catchment that generates in excess of these volumes): • Cargo Road 10 ML • Escort Way 13 ML • Somerset Park 6.3 ML • Burrendong Way 5.8 ML
Each wetland is designed as a stormwater management wetland and includes an inlet zone, macrophyte zone(s), and an outlet zone. Where possible a high flow diversion is incorporated. Each wetland system is designed to surcharge by 0.5 to 0.6 m during a runoff event to capture the design volume. This is released via an orifice plate control over about four to five days.
The slow release from the Ploughmans Creek wetlands is extracted using a small capacity harvesting pump (50 L/s) located on Ploughmans Creek just upstream of the Mitchell Highway (known as Pump Station 4 (PS4)). This pump transfers the harvested stormwater along an existing and then new rising main to the 230 ML holding pond constructed as part of the BSCSHS. From here the water is treated and transferred to Suma Park Dam to supplement the raw water supplies.
Two smaller pump stations (each 20 L/s) are used to transfer the slow release from the Somerset Park wetland (Pump Station 6 (PS6)) and Brooklands wetland (Pump Station 5 (PS5)) into the rising main.
Operating Rules
The current operating rules for the PCSHS are listed in Table 3.18. These are included in the scheme licence.
Table 3.18 – PCSHS Operating Rules
Number Operating Rule
1 Holding Pond Capacity Stormwater harvesting pumps will not operate if the holding pond is at capacity (200 ML)
2 Pump Controls PS4: Pumps start when creek flow > 55 L/s Pumps stop when flow falls to 5 L/s Flow measured at V-notch weir immediately downstream of pump extraction point PS5: Pumps start when creek flow > 20 L/s Pumps stop when water level returns to normal water level Pond depth measured by level sensor on outlet box PS6: Pump start when creek flow > 20 L/s Pump stop when flow falls to 2 L/s Flow measured at V-notch weir immediately downstream of pump extraction point
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Table 3.18 – PCSHS Operating Rules
Number Operating Rule
3 Maintenance of Downstream Flow During Harvesting PS4: Maintain minimum flow of 5 L/s Flow measured at V-notch weir immediately downstream of pump extraction point PS5: Maintain minimum flow of 2 L/s Flow controlled by actuated valve on 250 mm low flow pipe PS6: Maintain minimum flow of 2 L/s Flow measured at V-notch weir immediately downstream of pump extraction point
4 Stakeholder Engagement Representation from downstream stakeholders will be included in the review of the Operating Rules.
3.3.1.4 Water Quality Approval Process for Stormwater Harvesting
The NSW Office of Water (NOW) in consultation with the NSW Department of Health (now Ministry of Health (MoH)) and the Department of Environment, Climate Change and Water (now Environment Protection Authority (EPA)) has documented an approval framework for the transfer of treated stormwater to Suma Park Reservoir. This framework is outlined in Figure 26.
The process is represented as a series of gates, with the requirement of getting through the first gate and complying with its conditions before attempting the second gate. The three gates in the process are as follows: • Gate 1 – Extracting water from Blackmans Swamp Creek: compliance with NOW Section 22A approval (the Emergency Approval). Status: comply; • Gate 2 – Storing water in the holding dam: compliance with NSW Dams Safety Committee conditions. Status: comply; and • Gate 3 – Transferring water to Suma Park Dam (town water supply - water quality condition). Status: in progress. This gate applies to both stormwater harvesting schemes.
Gate 3 includes a three step process of process commissioning, trial production and full production. To date the process commissioning has been undertaken (until the point where the scheme stopped operating due to full dams) with the scheme firstly operated in batch mode and then continuous mode to monitor water quality. The reporting requirements (refer to Figure 26) of this step are being completed.
Trial production is likely to last for 18 months or so; its timing dependent on licensing and water storage levels. A detailed review will be prepared at the end of the trial production phase with review provided by NOW, MoH and the EPA.
Full production is the final stage. The three agencies are to agree on the issue of water quality approval for the operation of the stormwater harvesting schemes to move from trial production to full production. Written approval will be required from all three agencies.
Legislatively, the joint approval will be based on Section 60 to 64 of the Local Government Act, 1993 (NOW), Section 10A to 10M of the Public Health Act, 2010 (MoH) and Part 3.1 (sections 42 to 45) and Part 5.3 (Sections 120 to 123) of the Protection of the Environment Operations Act, 1997 (EPA).
The above water quality approval process applies to both harvesting schemes. Based on this approval process (and quite separate to the licensing) it is most likely that full production for the two existing stormwater harvesting schemes is some 3 to 5 years away.
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Process Commissioning Batch and continuous mode (15 to 20 samples) Minimum 500ML
Reports: • Design Report • WAE Plans • Draft Operating Manual • Water Quality Report Commissioning • Water Quantity Report Phase Audit • Catchment Hazard Report Identification • Refine Scheme End August 2010 Targets
NOW, MoH No & EPA Review
Yes
Trial Production 18 months (or so) Reports: • Complete design/WAE Report • Final Operating Manual • Water Quality Report • Water Quantity Report Trial Production • Full urban catchment Phase Audit audit Report • Complete actions from Risk Assessment ~18 months Workshop & REF • Final Scheme targets • Complete Risk Management Plan
NOW, MoH No & EPA Review
Yes
Full Production
Figure 26: NSW Office of Water approval framework – Water quality
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3.3.1.5 Performance of Existing Schemes
Average Harvest Volume – Approved Schemes
The REF prepared for the BSCSHS (Geolyse, 2008b) presented model results for the catchment yield and potential stormwater harvest volume. It was estimated that the average catchment runoff to the harvest point was 11,870 ML/year and the average annual harvest volume 1,300 ML/year (11% of the average annual streamflow). Initial operational data from the scheme was used to refine the long term modelling of how the scheme would perform. This revised modelling reduced the average catchment yield to 9,479 ML/year and lowered the predicted average scheme harvest in Stage 1 from 1,300 ML/year to around 800 ML/year, operating on a 100% Suma Park Reservoir trigger. The revised harvest volume represents about 8% of the average annual streamflow.
However, as noted above, the BSCSHS cannot be used whenever Suma Park Reservoir is above 50%. The average extraction under this operational trigger is 199 ML/year (2.1% of the average annual streamflow). This is the average harvest from BSCSHS Stage 1a.
Modelling of the PCSHS on its own indicates the scheme can add an average of between 700 to 800 ML/year to the city’s water raw water supplies (Geolyse, 2009b). The potential harvest from the scheme increases as the catchment becomes fully developed.
The combined input from the two schemes is less than the straight addition due to the interaction of the scheme holding pond. Table 3.19 provides a summary of the existing scheme performance operating in accordance with the approved operating rules.
All modelling was based on the existing Suma Park Reservoir volume of 17,290 ML.
Table 3.19 – Summary of harvest volumes from approved stormwater harvesting schemes
Catchment Average Annual Average Volume Proportion of Streamflow Harvested Streamflow Harvested ML/year ML/year
Blackmans Swamp Creek 9,479 193 2%
Holding Pond 209 156 75%
Ploughmans Creek 3,057 509 17%
Total – Blackmans system 9,688 349 4%
Total – Ploughmans system 3,057 509 17%
Total – both schemes 12,745 858 7%
Secure Yield
Water balance modelling was used to estimate the secure yield from BSCSHS Stage 1a and PCSHS.
Adding input from the two approved stormwater harvesting schemes is estimated to increase the secure yield of the water supply system by 900 ML/year.
Costs
The capital costs for the two stormwater harvesting schemes was: • BSCSHS $5.0 million • PCSHS $4.1 million
Orange City Council obtained 50% State Government funding for the two schemes.
The average annual operating cost for the two schemes operating in accordance with the approvals is $508,000 per year.
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The total cost of secure yield supplied is $1,295 per ML increase in secure yield (not allowing for the State Government grant).
3.3.2 BLACKMANS SWAMP CREEK 100% TRIGGER As discussed in Section 3.3.1.1, the current approval for the BSCSHS does not allow its use whenever Suma Park Reservoir is above 50%. Obtaining a licence to use this harvesting scheme at times when Suma Park Reservoir is less than 100% increases the system harvest capacity and secure yield. This option is called BSCSHS Stage 1b. Gaining full approval for the Stage 1 harvesting scheme is part of Council’s BAU scenario.
3.3.2.1 Performance and Impact on Flow Regimes
Table 3.20 provides a summary of the performance of the combined stormwater harvesting schemes both operating on a 100% trigger.
Table 3.20 – Summary of harvest volumes from stormwater harvesting schemes on 100% trigger
Catchment Average Annual Average Volume Proportion of Streamflow Harvested Streamflow Harvested ML/year ML/year
Blackmans Swamp Creek 9,479 762 8%
Holding Pond 209 86 41%
Ploughmans Creek 3,057 499 16%
Total – Blackmans system 9,688 848 9%
Total – Ploughmans system 3,057 499 16%
Total – both schemes 12,745 1,347 11%
Figure 27 shows the flow duration curve (FDC) for Blackmans Swamp Creek for three conditions: • Natural – this was estimated by removing impervious areas from the catchment model (brown line); • Existing – the FDC developed from modelling of the existing catchment development (red line). This line sits higher than the natural FDC and indicates the increase in runoff caused by catchment development; and • BSC Stage 1 – the FDC downstream of the harvesting scheme (blue line). The difference between the existing (red line) and harvesting FDC’s (blue line) represents the impact of the harvesting scheme. The flow duration curve for the Stage 1 operation shows that the harvesting scheme only reduces moderate to high flows – those that occur 25 per cent of the time or less. Importantly, operation of the scheme does not impact on low flows in the creek system (i.e. those that occur between 80 and 95 per cent of the time).
3.3.2.2 Secure Yield Water balance modelling was used to estimate the additional secure yield from BSCSHS Stage 1b and PCSHS.
Adding input from the two stormwater harvesting schemes both operating on a 100% trigger is estimated to increase the secure yield of the water supply system by 200 ML/year above the current approved schemes.
The total secure yield provided by the BSCSHS Stage 1 and PCSHS harvesting schemes is therefore 1,100 ML/year (i.e. 900 + 200 ML/year).
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3.3.2.3 Costs
There would be no capital costs for this option; simply a change in operating rule.
The average annual operating cost for the Stage 1 harvesting scheme operating on a 100% trigger is $594,000 per year (i.e. an increase of $86,000 per year).
The cost of secure yield supplied is $428 per ML increase in secure yield.
The overall cost of the secure yield supplied by the combined harvesting schemes falls to $1,137 per ML increase in secure yield (excluding grants).
Existing BSC Stage1 Natural
10000
1000 Average Annual Harvest (BSC+PC) = 1347 ML/year
Extracted from BSC = 762 ML (8%)
100 ML/day
10
1
0.1 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % time equalled or exceeded
Figure 27: BSCSHS Stage 1 flow duration curves
3.3.2.4 Summary
Table 3.21 summarises the option of gaining full approval for the BSCSHS Stage 1 stormwater harvesting as part of the water supply system.
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Table 3.21 – Summary of Option SH0: BSCSHS Stage 1b
Measure Result
Capital cost, $ nil
Operating cost, $/year $86,000
NPV – capital cost, ($2010) nil
NPV – operating cost, ($2010) $1,265,000
Potential increase in secure yield, ML/year 200
Capital costs, $/ML increase in secure yield nil
Operating costs, $/ML increase in secure yield $428
Total cost of secure yield supplied, $/ML increase in secure yield $428
Change in TRB if adopted $3 per assessment
Greenhouse Gas Emissions (operating power only) 0.58 tonnes CO2e/ML
Issues to consider • Licensing - current issues with obtaining permanent licence • Water quality risk assessment – may be too much stormwater; need to comply with NOW water quality approval process • Impact on flow regimes in Blackmans Swamp Creek and Summer Hill Creek
Likely timeframe to complete 3 to 5 years
3.3.3 BLACKMANS SWAMP CREEK STAGE 2 3.3.3.1 Conceptual Design
Stage 2 of the Blackmans Swamp Creek Stormwater Harvesting Scheme is part of Council’s BAU scenario and includes: • an off-line wetland upstream of the harvest weir adjacent to the creek near the intersection of Jilba and Phillip Streets. The conceptual wetland provides 14 ML of permanent water (below normal water level) and 36 ML of air space (to spillway level) for harvesting; • a controlled outlet from the wetland to the creek; and • removal of one of the existing pumps from the existing main harvesting pump station (PS1) and installation of an 80 L/s pump.
The location of the off-line wetland is shown on Figure 23 while a conceptual layout is provided on Figure 28. The conceptual wetland provides 14 ML of permanent water (below normal water level) and 36 ML of air space (to spillway level) for harvesting.
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Figure 28: BSCSHS Stage 2 conceptual offline wetland system
3.3.3.2 How it would Work
The Stage 2 harvesting scheme would operate in conjunction with Stage 1 as follows. • Weirs would control flow into the off-line wetland. Low flows would continue along the creek and the wetland would be ephemeral, with the water level rising and falling in response to direct rainfall and evaporative losses. When flow in the creek reaches 100 L/s, water would start to divert into the wetland. The weirs would be set so that about 70% of the creek flow above 100 L/s is diverted to the wetland; • The water level in the wetland would be controlled by an outlet box and pipe. An orifice control in the outlet box would limit discharge from the wetland to 100 L/s. As the water level in the wetland increases above the outlet box, a controlled release of 100 L/s would commence. This would combine with the bypass flow in the creek and move downstream to the harvest weir. If the wetland fills, excess flow would be released via a spillway to the creek; • During a harvest event, the existing Stage 1 harvesting scheme would continue to operate with two 225 L/s pumps and the new 80 L/s pump operating at Pump Station 1 (PS1). The current Stage 1 operating triggers would apply (i.e. the pumps would start when the creek flow reaches 1,000 L/s); • On the receding limb of the hydrograph, the main harvest pumps (at PS1) would ramp down and stop once the level in the weir pool falls to 0.5 m above the 300 mm diameter through pipe (as per current Stage 1 operating rules). At this stage, there would be a continued slow release from the upstream wetland providing a flow of about 100 L/s into the harvest weir pool. The 80 L/s pump would continue to draw water from the weir pool; and • The 80 L/s pump would continue to operate until the upstream wetland returns to its normal water level.
3.3.3.3 Performance and Impact on Flow Regimes
Table 3.22 provides a summary of the performance of the combined stormwater harvesting schemes with BSCSHS Stage 2. The harvest volumes assume both schemes are operating on a 100% trigger.
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Table 3.22 – Summary of harvest volumes from BSCSHS Stage 2
Catchment Average Annual Average Volume Proportion of Streamflow Harvested Streamflow Harvested ML/year ML/year
Blackmans Swamp Creek 9,479 1,630 17%
Holding Pond 209 49 23%
Ploughmans Creek 3,057 482 16%
Total – Blackmans system 9,688 1,679 17%
Total – Ploughmans system 3,057 482 16%
Total – both schemes 12,745 2,161 17%
Figure 29 shows the flow duration curves (FDC) for BSCSHS Stage 2. The difference between the BSCSHS Stage 1 line (blue) and the Stage 2 line (light blue) shows the additional volume being harvested. Harvesting still occurs in the moderate to high flow range with no flow reduction in the low flow range.
The capture of storm flow in the wetland and slow release following a runoff event has the effect of increasing low flows in the system. The 95th percentile flow increases from 0.6 ML/day to around 1.0 ML/day.
The BSCSHS Stage 2 scheme harvests more water, but it achieves this by harvesting more in the larger events. There is no impact on moderate flows or low flows in the creek.
Existing BSC Stage1 BSC Stage 2 Natural
10000
1000 More water harvested from Average Annual Harvest (BSC+PC) = 2161 ML/year this portion of the flow curve Extracted from BSC = 1630 ML (17%)
100
Increase in low flows ML/day
10
1
0.1 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % time equalled or exceeded
Figure 29: BSCSHS Stage 2 flow duration curves
3.3.3.4 Secure Yield
Water balance modelling of the Blackmans Swamp Creek harvesting scheme estimates the Stage 2 scheme could increase secure yield of the water supply system by 900 ML/year.
PAGE 67 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
3.3.3.5 Preliminary Cost Estimates
Preliminary capital cost estimates for the system are provided in Table 3.23.
Table 3.23 – BSCSHS Stage 2 – preliminary cost estimates
Item Cost ($’000)
Capital works – land, wetland, structures, pumps $4,000
Controls $100
Approvals $250
Survey, investigation, design and project management (15%) $615
Contingency (15%) $745
Total $5,710
Annual operating costs based on an average annual harvest of 1,630 ML/year are $324,000/year as follows: • Power $156,200/year • Treatment $37,400/year • Maintenance $130,000/year
These are the additional running costs above the operating costs for BSCSHS Stage 1.
3.3.3.6 Summary
Table 3.24 summarises the option of using BSCSHS Stage 2 as part of the water supply system.
Table 3.24 – Summary of Option SH1: BSCSHS Stage 2
Measure Result
Capital cost, $ $5,709,750
Operating cost, $/year $324,000
NPV – capital cost, ($2010) $6,010,000
NPV – operating cost, ($2010) $4,780,000
Potential increase in secure yield, ML/year 900
Capital costs, $/ML increase in secure yield $452
Operating costs, $/ML increase in secure yield $360
Total cost of secure yield supplied, $/ML increase in secure yield $812
Change in TRB if adopted $30 per assessment
Greenhouse Gas Emissions (operating power only) 0.66 tonnes CO2e/ML
Issues to consider • Licensing - current issues with obtaining permanent licence. Need to gain Stage 1 approval/licensing first • Does not promote diversification of water resources • Water quality risk assessment – may be too much stormwater; need to comply with NOW water quality approval process • Impact on flow regimes in Blackmans Swamp Creek and Summer Hill Creek • Draft Water Sharing Plan considerations
Likely timeframe to complete 4 to 6 years
PAGE 68 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
3.3.4 BLACKMANS SWAMP CREEK STAGE 3 3.3.4.1 Conceptual Design
Conceptually Stage 3 would require the following work: • construction of a larger harvest weir across the creek at the location of the existing harvest weir. The larger weir would have control gates to manage flow and would create an on-line weir pool of about 40 ML. The weir configuration would be as proposed in the original REF (Geolyse, 2008); • construction of a new access road to the Sewage Treatment Plant off Astill Drive; • upgrade to the existing batch pond treatment system and associated pump stations to double its capacity to 300 L/s. This would include a packaged treatment plant for settling and filtration; • duplication of the rising main from the batch ponds to Suma Park Dam and upgrade to the transfer pump station; and • modification to power and control systems.
The main component of the Stage 3 works, the larger harvesting weir, is shown on Figure 30.
Figure 30: BSCSHS Stage 3 conceptual harvesting weir
3.3.4.2 How it would Work
Stage 3 would include the construction of a gated weir at the location of the existing harvesting weir to create a weir pool (i.e. harvesting pond) of approximately 40 ML.
Modelling indicates that the establishment of a 40 ML harvesting pond above the weir would increase the annual stormwater harvest yield to an average of approximately 2,500 ML per year.
PAGE 69 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
The Stage 3 would work as follows: • Low flows would pass through the weir structure via large (3 m wide by 1.5 m high) box culverts. Once a pre-determined flow rate is reached (most likely the same 1,000 L/s trigger currently used), gates on the entry to the culverts would shut down to form the harvesting pond. The harvesting pumps would then commence extracting water from the pond at a rate of 450 L/s; • Once the harvesting pond is full, excess flows would overtop the spillway and continue along the creek. The gates would then automatically adjust to control flow over the spillway. At no time would the gates be fully closed. They would be operated to ensure a minimum downstream flow equivalent to 5 ML/day; • Stormwater from the harvesting pond would be pumped to the 230 ML holding pond for treatment and subsequent pumping to Suma Park Dam. The capacity of the treatment and transfer system would need to be doubled to ensure the system harvesting capacity is reached; and • The gates would open when the level in the weir pool fell to a pre-determined level, similar to the Stage 1 operation.
During a harvest event, the Stage 2 system would continue to operate as described in Section 3.3.2.4.
3.3.4.3 Performance and Impact on Flow Regimes
Table 3.25 provides a summary of the performance of the combined stormwater harvesting schemes with BSCSHS Stage 3. The harvest volumes assume all schemes are operating on a 100% trigger.
Table 3.25 – Summary of harvest volumes from BSCSHS Stage 3
Catchment Average Annual Average Volume Proportion of Streamflow Harvested Streamflow Harvested ML/year ML/year
Blackmans Swamp Creek 9,479 2,521 27%
Holding Pond 209 55 26%
Ploughmans Creek 3,057 455 15%
Total – Blackmans system 9,688 2,576 27%
Total – Ploughmans system 3,057 455 15%
Total – both schemes 12,745 2,976 23%
Figure 31 shows the flow duration curves (FDC) for BSCSHS Stage 3. The difference between the BSCSHS Stage 2 line (light blue) and the Stage 3 line (green) shows the additional volume being harvested.
The reduction in the green line in the range 0% to 50% shows how stormwater harvesting would reduce these flows – this is indicated by the green line moving to the left of the red line. The reduction in storm flows (those flows occurring less than 10% of the time) would benefit the downstream creek environment through reduced erosive forces. The harvesting does not reduce the stream flow below what is estimated to be the natural flow.
Proposed operating rules that would require the release of a base flow during harvesting have the effect of increasing low flows (those occurring 80% of the time or more) – which is indicated by the green line moving to the right of the red line.
PAGE 70 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Existing BSC Stage1 BSC Stage 2 BSC Stage 3 Natural
10000
1000 Average Annual Harvest (BSC+PC) = 2976 ML/year
Extracted from BSC = 2521 ML (27%)
Harvesting reduces peak flow 100 and volume during runoff events Low flows slightly increased ML/day
10
1
0.1 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % time equalled or exceeded
Figure 31: BSCSHS Stage 3 flow duration curves
3.3.4.4 Secure Yield
Water balance modelling of the Blackmans Swamp Creek harvesting scheme estimates the Stage 3 scheme could increase secure yield of the water supply system by 1,000 ML/year.
3.3.4.5 Preliminary Cost Estimates
Preliminary capital cost estimates for the system are provided in Table 3.23.
Table 3.26 – BSCSHS Stage 3 – preliminary cost estimates
Item Cost ($’000)
Harvest weir and gates $3,250
STP access road $750
Pumps $550
Treatment system $1,700
New rising main $1,688
Power and controls $500
Approvals $250
Survey, investigation, design and project management (15%) $1,303
Contingency (15%) $1,498
Total $11,489
PAGE 71 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Annual operating costs based on an average annual harvest of 2,521 ML/year are $231,000/year as follows: • Power $113,000/year • Treatment $13,000/year • Maintenance $231,000/year
These are the additional running costs above the operating costs for BSCSHS Stage 2.
3.3.4.6 Summary
Table 3.27 summarises the option of using BSCSHS Stage 3 as part of the water supply system.
Table 3.27 – Summary of Option SH2: BSCSHS Stage 3
Measure Result
Capital cost, $ $11,489,000
Operating cost, $/year $231,000
NPV – capital cost, ($2010) $12,254,000
NPV – operating cost, ($2010) $3,410,000
Potential increase in secure yield, ML/year 1,000
Capital costs, $/ML increase in secure yield $830
Operating costs, $/ML increase in secure yield $231
Total cost of secure yield supplied, $/ML increase in secure yield $1,061
Change in TRB if adopted $44 per assessment
Greenhouse Gas Emissions (operating power only) 0.55 tonnes CO2e/ML
Issues to consider • Licensing - current issues with obtaining permanent licence • Does not promote diversification of water resources • Water quality risk assessment – may be too much stormwater • Impact on flow regimes in Blackmans Swamp Creek and Summer Hill Creek • Draft Water Sharing Plan considerations
Likely timeframe to complete 6 to 8 years
3.3.5 BLACKMANS SWAMP CREEK MAXIMUM HARVESTING 3.3.5.1 Conceptual Design
The Blackmans Swamp Creek harvesting system could be modified beyond the proposed Stage 3 to increase the harvest volume. Conceptually this would involve: • excavating the area upstream of the harvest weir to provide a larger weir pool of around 70 ML; • increasing the main harvest pumps to 600 L/s; and • reducing the low flow during harvesting from 5 ML/day to 2 ML/day.
It is considered that this arrangement would represents the maximum harvesting opportunity on Blackmans Swamp Creek as it maximises the physical area available and adopts a minimal low flow rule during harvesting.
PAGE 72 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
3.3.5.2 Performance and Impact on Flow Regimes
Table 3.28 provides a summary of the performance of the combined stormwater harvesting schemes with maximum BSCSHS. The harvest volumes assume all schemes are operating on a 100% trigger.
Table 3.28 – Summary of harvest volumes from maximum BSCSHS
Catchment Average Annual Average Volume Proportion of Streamflow Harvested Streamflow Harvested ML/year ML/year
Blackmans Swamp Creek 9,479 3,042 32%
Holding Pond 209 27 13%
Ploughmans Creek 3,057 436 14%
Total – Blackmans system 9,688 3,069 32%
Total – Ploughmans system 3,057 436 14%
Total – both schemes 12,745 3,505 28%
Figure 31 shows the flow duration curves (FDC) for the maximum BSCSHS. The difference between the BSCSHS Stage 3 line (green) and the maximum line (purple) shows the additional volume being harvested.
The larger weir pool reduces the flows through to about the 90 percentile (the purple line is lower than the green line).
Existing BSC Stage1 BSC Stage 2 BSC Stage 3 Natural BSC Maximum
10000
1000 Average Annual Harvest (BSC+PC) = 3505 ML/year
Extracted from BSC = 3042 ML (32%)
Harvesting reduces peak flow 100 and volume during runoff events Low flows slightly increased ML/day
10
1
0.1 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % time equalled or exceeded
Figure 32: Maximum BSCSHS flow duration curves
3.3.5.3 Secure Yield
Water balance modelling of the Blackmans Swamp Creek harvesting scheme estimates the maximum scheme could increase secure yield of the water supply system by 700 ML/year.
PAGE 73 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
3.3.5.4 Preliminary Cost Estimates
Preliminary capital cost estimates for the system are provided in Table 3.29.
Table 3.29 – Maximum BSCSHS – preliminary cost estimates
Item Cost ($’000)
Harvest weir excavation $1,200
Pumps $200
Power and controls $250
Approvals $250
Survey, investigation, design and project management (15%) $285
Contingency (15%) $285
Total $2,470
Annual operating costs based on an average annual harvest of 3,042 ML/year are $141,000/year as follows: • Power $64,000/year • Treatment $7,000/year • Maintenance $70,000/year
These are the additional running costs above the operating costs for BSCSHS Stage 3.
3.3.5.5 Summary
Table 3.30 summarises the option of using maximum BSCSHS as part of the water supply system.
Table 3.30 – Summary of Option SH3: Maximum BSCSHS
Measure Result
Capital cost, $ $2,470,000
Operating cost, $/year $141,000
NPV – capital cost, ($2010) $3,235,000
NPV – operating cost, ($2010) $2,077,000
Potential increase in secure yield, ML/year 700
Capital costs, $/ML increase in secure yield $313
Operating costs, $/ML increase in secure yield $201
Total cost of secure yield supplied, $/ML increase in secure yield $514
Change in TRB if adopted $14 per assessment
Greenhouse Gas Emissions (operating power only) 0.04 tonnes CO2e/ML
Issues to consider • Licensing - current issues with obtaining permanent licence • Does not promote diversification of water resources • Water quality risk assessment – may be too much stormwater • Impact on flow regimes in Blackmans Swamp Creek and Summer Hill Creek • Draft Water Sharing Plan considerations
Likely timeframe to complete 6 to 8 years
PAGE 74 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
3.3.6 DOWNSTREAM STORMWATER HARVESTING ISSUES
The term “downstream stormwater harvesting” refers to those schemes that harvest stormwater downstream of the city (as opposed to upstream schemes discussed in Section 3.3.7).
Orange City Council has demonstrated innovation through the development of the existing stormwater harvesting scheme to supplement the city’s raw water supplies. However, there are remaining issues that need to be resolved before stormwater harvesting can be considered to be a permanent part of the long term water solution. • Sections of the NSW Office of Water have stated in various discussions that they consider stormwater harvesting not to be a long term option. This concern is based on water quality considerations. It was these concerns that lead to the development of the water quality approval process (refer to Section 3.3.1.4). This process must be completed before consideration would be given to scheme expansion; • Licensing of the Blackmans Swamp Creek scheme has been a protracted process and is still not resolved. Concerns relate to the flow regime in the Sumer Hill Creek system and while it has been demonstrated that the harvesting scheme does not impact on low flows, there is still concern from downstream licence holders relating to the ability to access their water entitlement. There is also an environmental concern relating to changes in the flow regime associated not only with harvesting, but with the removal of treated effluent from the system and the impact of Suma Park Dam. All of these aspects are related and Council has commissioned a detailed environmental flow study to determine the most appropriate management strategy for the Summer Hill Creek system. This study will help identify the level to which stormwater harvesting can occur; • Informal discussions with the NSW Office of Water licensing section indicate that it may be possible to gain approval for Stage 2 however Stage 3 (and more) is very unlikely to get licensed. Concerns are based on the potential impact on the creek system (Stage 3 harvesting increases the extraction from Blackmans Swamp Creek to 27%) and the large proportion that stormwater harvesting would make up in terms of raw water supply (an average of 55% of the unrestricted water demand); and • The Draft Water Sharing Plan for the Macquarie Bogan Unregulated and Alluvial Water Sources (NSW Office of Water, 2011) applies to the Summer Hill Creek water source. Clause 54(2) states:
A water supply work approval must not be granted or amended to authorise a new in-river dam in the following water sources:
(v) Summerhill Creek Water Source
This means that the proposed larger harvesting weir for BSCSHS Stage 3 could not be approved unless Ministerial approval was obtained. Other advice is that it would require an amendment to the Water Sharing Plan. This would make the approval process for Stage 3 extremely difficult and confirms the conclusion above that it is very unlikely to get licensed.
3.3.7 UPSTREAM STORMWATER HARVESTING 3.3.7.1 Description
The term “upstream” is used to describe potential stormwater harvesting in catchments that are upstream of the city. Potential locations for stormwater harvesting upstream of Orange were identified in 2007 during the assessment of the Blackmans Swamp Creek stormwater harvesting scheme. These include: • Blackmans Swamp Creek upstream of the railway at the location of an existing retarding basin; and • Rifle Range Creek on the Department of Primary Industry (DPI) dam.
PAGE 75 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
The location of these potential stormwater harvesting sites is shown on Figure 33.
Figure 33: Upstream stormwater harvesting locations
Upstream harvesting in Blackmans Swamp Creek could be located at the existing retarding basin situated on the southern side of the Orange to Parkes railway (refer to Figure 33). This location has a catchment area of 607 ha, which currently supports rural residential development, orchards and hobby farm activities. Parts of the catchment area are zoned for future development.
Conceptually a 40 ML harvesting pond could be constructed within the retarding basin area with outlet and controls to capture water during runoff events. The water collected in the pond could then be pumped via a rising main to Spring Creek Dam and treated before discharge to the reservoir.
Upstream harvesting in Rifle Range Creek could be located at the existing DPI dam (refer to Figure 33). This location has a catchment area of 263 ha, which currently supports rural residential development, orchards and hobby farm activities. Parts of this catchment are also zoned for future development.
Conceptually, by modifying the DPI dam, a 40 ML harvesting zone could be established above its normal water level. The water collected in the pond could then be pumped via a rising main to Spring Creek Dam (same rising main as the upstream Blackmans Swamp Creek system) and treated before discharge to the reservoir.
PAGE 76 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
The schemes could operate as follows: • The harvest ponds would be constructed with an outlet control with level sensors and automated valves; • During a runoff event, the pond would commence filling as the inflow exceeds the outflow capacity; • Once a pre-determined level is reached, the outlet pipe would close down (not fully) to limit the discharge to a flow equivalent to 2 ML/day; • If the event continued and filled the harvest pond, it would spill via a controlled spillway section. • Following the event the stored water in the pond would be pumped to Spring Creek Reservoir. The Blackmans Swamp Creek scheme was modelled using a 50 L/s pump (4.3 ML/day) and the Rifle Range Creek scheme a 40 L/s pump (3.5 ML/day); • A packaged treatment plant at Spring Creek Reservoir would treat the harvested water using coagulation, settling and filtration before discharge to the storage; and • The outlet pipe on the harvest ponds would open once the pond was pumped back to its normal operating level at the end of the harvesting event.
This is a similar operating protocol as used in the Ploughmans Creek stormwater harvesting scheme.
3.3.7.2 Performance
Potential average annual harvest volumes for these schemes were determined for two catchment development cases: existing and future development. Results are summarised in Table 3.31.
Table 3.31 – Upstream harvesting results
Catchment Harvest Pond Inflow Average Harvest Proportion of ML/year Volume Streamflow ML/year Harvested
Existing
Blackmans Swamp Creek 1,008 212 21%
Rifle Range Creek 437 106 24%
Total Existing 1,445 318 22%
Future Development
Blackmans Swamp Creek 1,211 273 23%
Rifle Range Creek 744 199 27%
Total Future Development 1,955 472 24%
A disadvantage with e upstream harvesting systems is that they reduce the flows through the system which would slightly reduce downstream harvesting volumes.
3.3.7.3 Secure Yield Estimate
Water balance modelling was used to estimate the secure yield provided by the upstream harvesting options as follows: • Existing catchment conditions 200 ML/year • Future catchment conditions 400 ML/year
3.3.7.4 Preliminary Cost Estimate
Preliminary capital cost estimates for the upstream harvesting system are provided in Table 3.32. Capital replacement of structures and pumps is included in future years.
PAGE 77 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Table 3.32 – Upstream stormwater harvesting – preliminary cost estimates
Item Cost ($’000)
Ponds (x2) $1,000
Pump stations (x2) $300
Rising mains $1,683
Treatment system $850
Power and controls $350
Approvals $200
Survey, investigation, design and project management (15%) $657
Contingency (15%) $657
Total $5,697
Annual operating costs based on an average annual harvest of 318 ML/year (existing catchment development) are $113,000/year as follows: • Power $28,000/year • Treatment $5,000/year • Maintenance $80,000/year
Under future catchment development the average annual operating costs increase to $130,000/year.
3.3.7.5 Summary
Table 3.33 summarises the option of using upstream stormwater harvesting as part of the water supply system.
Table 3.33 – Summary of Option SH4: Upstream stormwater harvesting
Measure Result
Capital cost, $ $5,697,000
Operating cost, $/year $113,000 - $130,000
NPV – capital cost, ($2010) $6,465,000
NPV – operating cost, ($2010) $1,666,000 - $1,922,000
Potential increase in secure yield, ML/year 200 - 400
Capital costs, $/ML increase in secure yield $2,188 - $1,094
Operating costs, $/ML increase in secure yield $564 - $325
Total cost of secure yield supplied, $/ML increase in secure yield $2,752 - $1,419
Change in TRB if adopted $22 per assessment
Greenhouse Gas Emissions (operating power only) 0.38 tonnes CO2e/ML
Issues to consider • Licensing - current issues with obtaining permanent licence for downstream harvesting options • Water quality risk assessment – may be too much stormwater • Impact on downstream harvesting schemes • Decentralised water treatment systems • Better option when catchment are developed
Likely timeframe to complete 3 to 5 years
PAGE 78 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
3.3.8 NORTHERN SUBURBS STORMWATER HARVESTING (BEER ROAD) 3.3.8.1 Conceptual Design
Areas on the northern side of Orange are zoned for residential development. Runoff volumes will increase as these areas are developed.
The Beer Road area was identified as a possible future stormwater harvesting location (refer to Figure 34). This location has a catchment area of 134 ha, which currently supports some residential development and open space.
Figure 34: Potential northern suburbs stormwater harvesting (Beer Road)
Conceptually a 5 ML harvesting pond (constructed wetland system) could be constructed within the drainage line with outlet and controls to capture water during runoff events. The water collected in the pond could then be pumped via a rising main to join with the existing stormwater rising main that runs along the North Orange bypass. Such a system could operate in the same way as described for the upstream stormwater harvesting options.
A 5 ML harvest pond and 50 L/s pump was modelled for the assessment of this option.
3.3.8.2 Performance
Potential average annual harvest volumes for this scheme were determined for two catchment development cases as follows: • Existing catchment conditions – potential average annual harvest volume 88 ML/year • Future catchment conditions – potential average annual harvest volume 129 ML/year
PAGE 79 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
3.3.8.3 Secure Yield Estimate
Water balance modelling was used to estimate the secure yield provided by the northern suburbs harvesting option as follows: • Existing catchment conditions 60 ML/year • Future catchment conditions 100 ML/year
3.3.8.4 Preliminary Cost Estimate
Preliminary capital cost estimates for the upstream harvesting system are provided in Table 3.34. Capital replacement of structures and pumps is included in future years.
Table 3.34 – Upstream stormwater harvesting – preliminary cost estimates
Item Cost ($’000)
Pond $750
Pump station $150
Rising main $425
Power and controls $350
Approvals $200
Survey, investigation, design and project management (15%) $281
Contingency (15%) $281
Total $2,438
Annual operating costs based on an average annual harvest of 129 ML/year (future catchment development) are $63,000/year as follows: • Power $12,000/year • Treatment $12,000/year • Maintenance $40,000/year
3.3.8.5 Summary
Table 3.35 summarises the option of using northern suburbs stormwater harvesting (Beer Road) as part of the water supply system. This summary is for future catchment conditions.
Table 3.35 – Summary of Option SH5: Upstream stormwater harvesting (Beer Road)
Measure Result
Capital cost, $ $2,438,000
Operating cost, $/year $63,000
NPV – capital cost, ($2010) $3,205,000
NPV – operating cost, ($2010) $937,000
Potential increase in secure yield, ML/year 100
Capital costs, $/ML increase in secure yield $2,171
Operating costs, $/ML increase in secure yield $634
Total cost of secure yield supplied, $/ML increase in secure yield $2,805
Change in TRB if adopted $11 per assessment
Greenhouse Gas Emissions (operating power only) 0.41 tonnes CO2e/ML
PAGE 80 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Table 3.35 – Summary of Option SH5: Upstream stormwater harvesting (Beer Road)
Measure Result
Issues to consider • Licensing – current issues with obtaining permanent licence for downstream harvesting options • Water quality risk assessment – may be too much stormwater • Better option when catchment is developed • Small system in terms of secure yield
Likely timeframe to complete 3 to 5 years
3.3.9 LONG LIST RECOMMENDATIONS
The following long list of stormwater harvesting options can be derived from the above assessment: • SH0: BSCSHS Stage 1b (included in BAU); • SH1: BSCSHS Stage 2 (included in BAU); • SH2: BSCSHS Stage 3; • SH3: maximum BSCSHS; • SH4: Upstream stormwater harvesting; and • SH5: Beer Road stormwater harvesting.
Further consideration and short listing of options is presented in Section 4.
3.4 RAINWATER TANKS
3.4.1 INTRODUCTION
Rainwater tanks provide a potential alternative water source and can reduce the demand on the mains water supply. Orange City Council has a rainwater tank rebate policy in place (ST061) that has had a good take-up rate and provided many local residents extra financial incentives to install a rainwater tank. This rebate is the largest financial water saving incentive Council offers.
There are a number of constraints which need to be considered to ensure that the most appropriate sized rainwater tank is installed. These include things such as rainfall, lot size, purpose of use and cost. Although larger rainwater tanks provide a greater capacity for storage and increased potential to reduce the demand on mains water, they are more expensive and may be restricted by planning controls and space. The effectiveness of larger rainwater tanks also becomes limited by the roof catchment area.
An analysis of rainwater tank systems was undertaken to: • Assess the impact of a range of rainwater tank sizes on mains water consumption for a number of different water uses for an average household; and • Estimate the annual water supply that could be provided by rainwater tanks.
The analysis was carried out using the spread sheet based Rainwater Tank Model (Version RTM 2.1) developed by DEUS (July, 2006).
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3.4.2 RAINWATER TANK REBATE POLICY
Orange City Council has a rainwater tank rebate policy in place (ST061). A review of this policy in October 2010 showed that on average only 10% of rebate recipients plumb the tank internally to the house. The policy was reviewed to provide a greater incentive to connect the rainwater tank for internal use. The rebates provided under the current policy are shown in Table 3.36.
Table 3.36 – Tank Rebate Policy ST061 – rebate schedule
Tank Capacity, L Tank Only Rebate Plumbed Internally into Premise
2,000 – 4,999 $100 $500
5,000 and above $250 $500
3.4.3 ASSESSMENT OF RAINWATER TANKS 3.4.3.1 Household Water Demand
The NSW per-capita benchmark for water as adopted in the DoP BASIX tool was used to estimate the typical household demand. This data is summarised in Table 3.37 and extended to a typical household in Orange with an average occupancy rate of 2.48 people per household.
Table 3.37 – Household water demand profile used for rainwater tank modelling
Water Use NSW Benchmark Orange Household L/person/day L/day
Internal Shower 56.9 141.1
Toilet 35.2 87.3
Washing machine 48.5 120.3
Kitchen sink 12.0 29.8
Bathroom basin 5.9 14.6
Dishwasher 2.9 7.2
Bath 8.7 21.6
Laundry trough 5.1 12.6
Leaks 1.8 4.5
Internal sub-total 177.1 439.0
External
Garden irrigation 52.9 131.2
Pool and spa 6.5 16.1
Car washing 0.7 1.7
Cooling tower/evaporative cooling 1.2 3.0
Fire test 1.9 4.7
Other 7.3 18.1
External sub-total 70.4 174.8
TOTAL 247.5 613.8
PAGE 82 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
3.4.3.2 Rainwater Tank Modelling
The aim of the rainwater tank modelling was to assess a number of different rainwater tank scenarios for an average house in the Orange area. Model scenarios were run using a variety of tank sizes and a combination of potential home rainwater uses as follows: 1. Outside use only – garden watering and car washing; 2. Outside use as well as internal toilet use; and 3. Outside use as well as internal toilet and washing machine cold water use.
These three scenarios provide a good indication of the effectiveness of rainwater tanks under different use scenarios. Each scenario is assessed against seven different tank sizes ranging from 1,000 to 30,000 L to determine the benefit to potable water usage and average water bill saving.
The DEUS rainwater tank model uses 20 years of historical rainfall and temperature data which was attained from SILO for the period 1 January 1981 to 31 December 2000. The average annual rainfall over this period was 890 mm which is consistent with Orange area long term rainfall averages as shown below: • Airport AWS (1966 to 2011) 866 mm • Airport comparison (1968 to 2011) 894 mm • Orange Post Office (1870 to 1968) 878 mm • Agriculture Research Station (1976 to 2011) 932 mm
Assumptions adopted for the rainwater tank model are presented in Table 3.38.
Table 3.38 – Assumptions and Input to the rainwater tank model
Item Value
Roof area draining to tank (m2) 300
First flush volume per storm (L) 20
Rainfall water lost due to wetting and evaporation (mm) 0.5
Roof runoff factor (overflow from gutters etc) (%) 90
Tank starting volume when first installed (L) 1
Annual average outside use (L/day) 175
Average daily toilet use (L/day) 87
Average daily washing machine cold water use (L/day) 102
Average daily household consumption (L/day) 614
Maximum mains top-up per day (L) 1,000
Water usage charge ($/kL) 1.60
Water access charge ($/year) 170.15
3.4.3.3 Financial Modelling
Financial modelling was used to calculate the current value of the water supplied by the rainwater tank system for each scenario. This modelling adopts a net present value (NPV) approach similar to that adopted by the NSW Independent Pricing and Regulatory Tribunal (IPART) for the metropolitan water utilities. The financial modelling was based on an assumed tank life of 30 years and a 7% discount rate.
PAGE 83 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Capital costs applied in the financial modelling are summarised in Table 3.39 for Scenario 1 and Table 3.40 for Scenarios 2 and 3. The installation cost for the latter two scenarios is higher due to the need to plumb internally. The higher rebate is included for these scenarios.
Table 3.39 – Tank and installation costs – Scenario 1
Tank Tank Pressure Labour Materials 10% OCC Total Volume Including Pump and Costs Contingency Rebate Delivery Rainsaver and L Installation
1,000 $750 $1,500 $400 $300 $295 0 $3,245
2,000 $950 $1,500 $600 $400 $345 -$ 100 $3,695
5,000 $1,400 $1,500 $800 $500 $420 -$ 100 $4,520
7,500 $2,000 $1,500 $1,000 $600 $510 -$ 250 $5,360
10,000 $2,200 $1,500 $1,000 $700 $540 -$ 250 $5,690
20,000 $3,000 $1,500 $1,200 $800 $650 -$ 250 $6,900
30,000 $4,500 $1,500 $1,200 $800 $800 -$ 250 $8,550
Table 3.40 – Tank and installation costs – Scenarios 2 and 3
Tank Tank Pressure Labour Materials 10% OCC Total Volume Including Pump and Costs Contingency Rebate Delivery Rainsaver and L Installation
1,000 $750 $1,500 $800 $300 $335 0 $3,685
2,000 $950 $1,500 $1,000 $400 $385 -$ 600 $3,635
5,000 $1,400 $1,500 $1,200 $500 $460 -$ 600 $4,460
7,500 $2,000 $1,500 $1,400 $600 $550 -$ 750 $5,300
10,000 $2,200 $1,500 $1,400 $700 $580 -$ 750 $5,630
20,000 $3,000 $1,500 $1,600 $800 $690 -$ 750 $6,840
30,000 $4,500 $1,500 $1,600 $800 $840 -$ 750 $8,490
The costs derived for the supply and installation of a rainwater tank were confirmed through obtaining a quotation from a licensed installer. This is included as Appendix A and indicates a price of $6,924.50 for a 10,000 L tank with pump and $6,407.50 for a 5,000 L tank with pump. These quoted prices are slightly higher than those used in the assessment.
Annual costs assumed the following: • Annual maintenance cost of $50 per year; • Power consumed by the pressure pump based on a 0.6 kW pump operating at 0.5 L/s pumping the annual volume determined from the rainwater tank model for each tank system; • Average power cost of $0.18/kWhr; and • Potable water savings based on $1.60/kL.
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3.4.4 RESULTS 3.4.4.1 Water Saving
Figure 35 illustrates the potential water saving for the three scenarios modelled for varying tank sizes.
The results show that the amount of potable water saved for each scenario is not proportional to the tank size. For Scenario 1 (outside use only) there is little benefit gained by tank sizes greater than 10,000 L. Larger tank volumes assist when more water is used from the tank (i.e. in Scenarios 2 and 3). The average annual potable water saving using a 10,000 L tank is: • Scenario 1 60.7 kL/year • Scenario 2 85.9 kL/year • Scenario 3 109.9 kL/year
The effectiveness of rainwater tanks increases with increased use of rainwater (i.e. for Scenarios 2 and 3). It should be noted that in these cases there are greater installation costs particularly in retrofitting rainwater tanks to internal plumbing to supply toilets and washing machines.
The rainwater tank model estimates the savings for an average household. Actual households may have different roof areas and water demand which will result in different water and financial savings.
Outside use Outside and toilet use Outside, toilet and washing machine cold water use
140
120
100
80
60 Potable water saving, kL/year saving, water Potable
40
20
0 0 5 10 15 20 25 30 Tank volume, kL
Figure 35: Rainwater Tank Analysis – Potential Household Water Saving
The following figures illustrate the results of the modelled scenarios. These show the volume of water saved, the number of days the tank is full each year and the percentage of water which will need to be supplied by the mains supply for the different sized rainwater tanks.
PAGE 85 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Water saving (kL/year) Days tank full (days/year) Potable topup (% of use)
140
120
100
80
60 Units Units legend) (see
40
20
0 0 5 10 15 20 25 30 Tank volume, kL
Figure 36: Scenario 1 – Rainwater tank size comparison for outside use only
Water saving (kL/year) Days tank full (days/year) Potable topup (% of use)
140
120
100
80
60 Units Units legend) (see
40
20
0 0 5 10 15 20 25 30 Tank volume, kL
Figure 37: Scenario 2 – Rainwater tank size comparison for outside and toilet use
PAGE 86 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Water saving (kL/year) Days tank full (days/year) Potable topup (% of use)
140
120
100
80
60 Units Units legend) (see
40
20
0 0 5 10 15 20 25 30 Tank volume, kL
Figure 38: Scenario 3 – Rainwater Tank Size Comparison for Outside, Toilet Use and Washing Machine
3.4.4.2 Rainwater Tank Financial Analysis
Table 3.41 provides a summary of the rainwater tank financial analysis. For each scenario, the optimum tank size (in terms of cost of the water supplied) is 5,000 L. The larger tank sizes (7,500 L and 10,000 L) are only marginally more expensive (in terms of the cost of water supplied) for the scenarios that use more of the rainwater (i.e. in Scenarios 2 and 3).
Table 3.41 – Summary of rainwater tank financial analysis
Tank Tank and Potable Annual Annual Net Annual Rainwater Volume Installation Water Water Bill Operating Saving Cost Cost Savings Saving and Maintenance L $ kL/year $/year $/year $/year $/kL
Scenario 1 – Outside use only
1,000 $3,245 11.4 $18.27 $50.68 -$32.41 $24.07
2,000 $3,695 36.8 $58.82 $52.21 $6.61 $7.31
5,000 $4,520 54.5 $87.27 $53.27 $34.00 $5.56
7,500 $5,360 58.5 $93.67 $53.51 $40.16 $6.15
10,000 $5,690 60.7 $97.12 $53.64 $43.48 $6.27
20,000 $6,900 63.6 $101.75 $53.82 $47.93 $7.34
30,000 $8,550 63.7 $101.89 $53.82 $48.07 $9.26
Scenario 2 – Outside and toilet use
1,000 $3,685 18.9 $30.23 $51.13 -$20.90 $15.65
2,000 $3,635 47.5 $76.01 $52.85 $23.16 $5.22
5,000 $4,460 74.6 $119.29 $54.48 $64.81 $3.59
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Table 3.41 – Summary of rainwater tank financial analysis
Tank Tank and Potable Annual Annual Net Annual Rainwater Volume Installation Water Water Bill Operating Saving Cost Cost Savings Saving and Maintenance L $ kL/year $/year $/year $/year $/kL 7,500 $5,300 82.0 $131.13 $54.92 $76.21 $3.89
10,000 $5,630 85.9 $137.52 $55.15 $82.37 $3.93
20,000 $6,840 93.0 $148.73 $55.58 $93.15 $4.48
30,000 $8,490 95.0 $152.02 $55.70 $96.32 $5.65
Scenario 3 – Outside, toilet and cold water washing machine use
1,000 $3,685 27.1 $43.30 $51.63 -$8.33 $10.45
2,000 $3,635 57.2 $91.46 $53.43 $38.03 $4.07
5,000 $4,460 92.6 $148.13 $55.56 $92.57 $2.59
7,500 $5,300 103.5 $165.29 $56.21 $109.08 $2.76
10,000 $5,630 109.9 $175.80 $56.59 $119.21 $2.74
20,000 $6,840 122.3 $195.61 $57.34 $138.27 $3.04
30,000 $8,490 127.9 $204.61 $57.67 $146.94 $3.80
The data in Table 3.41 indicates that there is no financial benefit for households to install rainwater tanks. The cost of the water supplied from the system is greater than the 2010/2011 water usage charge of $1.60/kL.
3.4.5 USE OF RAINWATER TANKS AS A WATER SUPPLY OPTION
A benefit of rainwater tanks may be an increase in secure yield (through reduced demand) and possibly the postponing of major water security works.
The number of residential assessments in 2010/2011 is 14,542. If 70% of households (10,179 households) installed a 10,000 L rainwater tank connected for outdoor and toilet use, the annual supply from all the tanks in an average year would be in the order of 874 ML. However this figure is not a secure yield as it is likely to be significantly lower in dry years – which are the years that impact the most on the secure yield.
As rainwater tank systems would require potable top-up, they would be subject to water restrictions as the city’s water storages are drawn down. In these periods rainwater tanks would mainly supply internal uses with an associated reduction in potable water saving. This would further reduce the benefit of rainwater tanks system on secure yield.
Given the above, it is considered that the secure yield from 10,179 rainwater tanks would be in the order of 200 to 300 ML/year. While beneficial, it is unlikely to impact on the need for and timing of other major water security works.
The installation of rainwater tanks would reduce catchment runoff and, potentially, the yield from the two stormwater harvesting schemes. As input from the harvesting schemes is used to boost the system secure yield, a reduction in capacity of the harvesting schemes would reduce the secure yield. However, on the demand side, rainwater tanks would reduce the total water demand, so a lower secure yield may be acceptable. Without undertaking detailed modelling of this interaction, it is assumed that the potential reduction in secure yield from the harvesting schemes would be minor and the reduction in demand achieved by the rainwater tanks would represent an increase in secure yield.
Given that there is no financial benefit for households to install rainwater tanks it is likely this option would need to be funded by Council to ensure high uptake. The average cost of installing a 10,000 L
PAGE 88 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL rainwater tank system connected for outdoor and toilet use (excluding the rebate) is $6,380 which equates to a total cost of $64.94 million. Assuming the upper end of the secure yield increase from the use of rainwater tanks, and a 10 year installation timeframe, would result in a cost of $11,044 per ML increase in secure yield.
3.4.6 SUMMARY
Table 3.42 summarises the option of using rainwater tanks as part of the water supply.
Table 3.42 – Summary of Option RW1: Rainwater tanks
Measure Result
Capital cost, $ $64,942,000
Operating cost, $/year Nil
NPV – capital cost, ($2010) $45,613,000
NPV – operating cost, ($2010) Nil
Potential increase in secure yield, ML/year 300
Capital costs, $/ML increase in secure yield $11,044
Operating costs, $/ML increase in secure yield Nil
Total cost of secure yield supplied, $/ML increase in secure yield $11,044
Change in TRB if adopted $140 per assessment
Greenhouse Gas Emissions (operating power only) Negligible
Issues to consider • Level of household uptake • Water quality risks • Low secure yield
Likely timeframe to complete >10 years
3.4.7 LONG LIST RECOMMENDATION
The potential use of using rainwater tanks as part of the long term water supply is included in the long list of options.
Further consideration and short listing of options is presented in Section 4.
3.5 GROUNDWATER
3.5.1 SPRING HILL AND LUCKNOW
Spring Hill and Lucknow are supplied with water from four boreholes which are licensed under Section 12 of the Water Act, 1912 for the extraction of water for town water supply. The water is chlorinated and pumped to storage tanks from which it is distributed to the villages. The village of Spring Hill is serviced from the Spring Hill reservoir and a portion of the water is gravity fed to Lucknow reservoir. Both reservoirs service their reticulation systems through gravity feed.
The four bores have a combined capacity of 0.58 ML/day. Some peak day flow above this capacity is provided by the service reservoirs.
The volume of water extracted from the bore system for town water supply in any one year is limited by licence to 75 ML/year (licence 80BL025285). Current annual demand is within this limit being around 67 ML/year. Forecast peak day water demand remains within the capacity of the existing bores under the Business as Usual scenario. The annual water extraction for town water supply could slightly exceed the licence limit after 2038 under a high growth scenario (refer to Technical Note 3).
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The existing groundwater resource provides a consistent and reliable supply source for the villages of Spring Hill and Lucknow.
3.5.2 EXISTING GROUNDWATER RESOURCES FOR ORANGE
Table 3.43 lists existing groundwater bores that form part of the Orange water supply. The location of each bore is shown on Figure 39.
Table 3.43 – Orange town water supply bores
Bore Licence Location Licensed Annual Volume for Town Water Supply
80BL245947 Works Depot Total 280 ML/year
80BL245074 Showground
80BL245800 Clifton Grove - Shearing Shed Total 182 ML/year
80BL245805 Clifton Grove - Bore 5
Total 462 ML/year
Figure 39: Orange water supply bores
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Initially Council held a licence to extract only 75 ML/year from the Showground bore. As part of Council’s BAU scenario, bore impact management plans (BIMPs) were prepared for the bore system and licence applications lodged. These were favourably determined in March 2012 and together these bores are licensed to extract 462 ML/year.
The Clifton Grove and Showground bores are currently connected to Suma Park Reservoir. Works are required to deliver water from the Depot bore to the water supply system. This work will be undertaken.
The constant daily supply from bores equates to a direct increase in secure yield. Therefore the increased licensed extraction increases the secure yield from the bore system by 350 ML/year (i.e. from 100 to 450 ML/year).
A summary of this option is provided in Table 3.44. Capital costs are associated with minor infrastructure works (connections) and additional testing. Capital replacement cost is included in future years.
Table 3.44 – Summary of Option GW1: Bores
Measure Result
Capital cost, $ $250,000
Operating cost, $/year $285,000
NPV – capital cost, ($2010) $316,000
NPV – operating cost, ($2010) $4,213,000
Potential increase in secure yield, ML/year 350
Capital costs, $/ML increase in secure yield $61
Operating costs, $/ML increase in secure yield $815
Total cost of secure yield supplied, $/ML increase in secure yield $876
Change in TRB if adopted $12 per assessment
Greenhouse Gas Emissions (operating power only) 1.35 tonnes CO2e/ML
Issues to consider • Water quality risks • Licensing (resolved March 2012)
Likely timeframe to complete 1 to 2 years
3.5.3 POTENTIAL GROUNDWATER RESOURCES
Orange City Council and Centroc have commissioned various studies to identify potential groundwater resources in the Orange area. Three possible areas of groundwater have been investigated: • The Orange basalt areas to the south of the town; • Possible bore locations in north Orange along the north Orange bypass and harvesting pipeline route and possible bore locations in or nearby parks and reserves in Orange; and • Managed aquifer recharge (MAR).
3.5.3.1 Orange Basalt Areas
Investigations of the Orange basalt area to the south of the city are presented in the following reports: • C M Jewell & Associates (2004) Groundwater Supply Investigation, Orange. J1036.2R; • C M Jewell & Associates (2008) Review of Groundwater Assessment, Orange. J1036.4R; and • C M Jewell & Associates (2009) Orange Basalt Groundwater Resources. J1412.3R.
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The 2004 report provided a preliminary assessment of groundwater resources to supplement municipal water supply sources focusing on area to the south of Orange which overlies the Orange basalts.
The Orange Basalts refers to the area south of Orange, where basalts form an extensive series of lava plains resulting from the outpouring of several eruptions from Mount Canobolas during the Tertiary Period.
Groundwater resources are predominantly associated with the numerous basalt units that comprise the Orange basalts, hosted by secondary porosity features such as joints, voids, gravel units and fractures, whilst minor flows associated with weathered horizons and lithological contrasts are thought to contribute to the movement of groundwater within perched horizons, particularly within the weathered profile of the rock mass. They are generally favourable areas for boreholes, and are also known for their association with useful springs. Borehole depths within the basalts vary considerably, from 10 to 140 metres. The primary source of groundwater recharge in the area is the infiltration of soil-water.
The Orange basalt aquifer is used extensively for irrigation and stock and domestic purposes, and groundwater is also used for municipal water supplies.
The report highlighted that there is an embargo on new licences for groundwater extraction; however, bores for town supply are exempt.
Four regions were proposed for further investigation, on the basis of their potential to contain deep basalt aquifer zones. Quality is expected to be acceptable, although decreasing down the list. 1. Off Forest Road; 2. Near Orange Airport; 3. Between Spring Hill and Lucknow; and 4. West of Spring Creek Reservoir.
The 2008 review provided a program of the work required to take recommendations from the 2004 Groundwater Supply Investigation to the feasibility stage. It proposed six drilling targets across the four zones, to obtain hydrogeological data and set out a program of work and specification for drilling contractors.
The report also discussed resource sustainability because the Orange Basalt aquifer is already heavily used, and has been declared a water shortage area. It is likely that use of the aquifer for municipal water supply would be at the expense of existing (primarily agricultural) users. Aquifer Storage and Recover (ASR) was presented as an option for aquifer management. ASR is the practice of storing water in an aquifer when supply is plentiful through injection into a borehole and the recovery of water from the same borehole during times of need (see discussion below).
A further review of the Orange basalt groundwater resources was undertaken in August 2009. This report was prepared for MWH as technical input to the Centroc regional water security study (MWH, 2009).
3.5.3.2 North Orange Groundwater Resources
A hydrogeological assessment of the northern suburbs of Orange was undertaken to gain a clear understanding of the availability of groundwater resources in this area to supplement existing water supplies. Of particular interest are borehole locations close to the stormwater harvesting rising main, as well as within or in close proximity to a number of public parks and reserves.
Groundwater in this area is hosted in a regionally extensive fractured-rock aquifer. Units thought to be of importance to this investigation include the Oakdale Formation – which consists of Ordovician-aged volcanic sandstones, basalt, siltstone, shale, chert, conglomerate and breccia and underlies most of the area to the north of the city centre, and the unnamed grouping of ultramafic cumulates and lavas
PAGE 92 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL to the northeast of the city centre. It appears that the fractured rocks along the alignment of the Ammerdown Fault and the unnamed anticline, which runs along the eastern outskirts of Orange, offer the greatest exploration potential.
Minor alluvial aquifers are located along the alignments of locally significant waterways – including those of the Broken Shaft, Ploughmans and Blackmans Swamp creeks – but these are expected to have minimal storage and not to be of significance. The unnamed monzonite intrusives which underlie much of the Suma Park Reservoir to the north-east of the city centre are expected to offer low exploration potential, whilst the tertiary-aged basalts – which offer excellent exploration potential to the south of Orange – do not occur in the study area.
Yields throughout the area are usually no more than 1.0 litres per second (L/s), and typically less than 0.5 L/s. Quality is expected to be sufficient for general water supply purposes.
Three areas of exploration in North Orange were proposed, around the brittle deformation features associated with: 1. The Ammerdown Fault; 2. The unnamed anticlinal hinge on the eastern outskirts of Orange; and finally 3. The thrust faults and block deformation structures associated with the emplacement of the Ordovician lavas and monzonites near the Suma Park Reservoir.
Eight drilling locations in North Orange or in close proximity to a public park or reserve were proposed and pumping test procedures stipulated:
A Mitchell Highway and March Road.
B East of Clergate Road at Farrell Road.
C Eastern end of North Orange bypass on ‘Wolumla’ property.
D Kooronga Avenue Oval.
E Ploughmans Creek Reserve.
F Botanic Gardens.
G Clergate Road Reserve.
H Cook Park.
3.5.3.3 Summary of Groundwater Resource Investigations
The investigations to the south and north of the city indicate that there is some potential to utilise groundwater resources as part of the water supply system. The Orange basalt is a good aquifer, but it is difficult to predict yields and hard to control impacts on existing groundwater users. The fact that there is an embargo in place for these aquifers supports this. Despite the fact that town water extraction is exempt, there is a reasonable potential that any groundwater extraction in this source would detrimentally impact on other users.
Areas in the north of Orange also show some potential. However the typical groundwater yields are very low and would not appear to offer substantial potential to supplement town water supplies.
The conclusion from these investigations is that a groundwater options would be best used in conjunction with surface water resources through a Managed Aquifer Recharge scheme.
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3.5.3.4 Managed Aquifer Recharge
Description
Managed Aquifer Recharge (MAR) is the intentional recharge of water to aquifers to supplement natural recharge processes, in such a way that the water is available for subsequent recovery or environmental benefit. Management is provided to ensure adequate protection of human health and the environment. It is not a new concept and has been in use, formally and informally, for decades.
A wide range of MAR technologies have been developed. These include: • single-well systems, where water is injected and recovered from the same borehole; • multi-well artificial recharge systems, where water is injected and recovered from different boreholes; and • recharge augmentation using dams, contour banks, basins, channels and galleries.
Many MAR techniques are only applicable in areas where there is an upper, unconfined aquifer to which water can infiltrate from surface watercourses or engineered structures. Where aquifers are confined by low-permeability layers, as is generally the case in the Lachlan Fold Belt aquifers, only well (borehole) recharge methods can be used.
Well recharge methods are commonly divided into: • Aquifer Storage and Recovery (ASR) – where a single well is used for recharge and recovery; and • Aquifer Storage, Transfer and Recovery (ASTR) – where separate wells are used for recharge and recovery. In some cases, ASTR can involve the use of complex well-fields.
Both systems are potentially viable in Orange (C M Jewell & Associates, 2011).
For Orange, MAR would provide a means of increasing raw water storage. By itself, it does not provide an additional water source; simply a means for storage and later retrieval of water. Water for recharging the aquifer would need to be sourced from somewhere.
Business Case Managed Aquifer Recharge
A review of the feasibility of using MAR was undertaken in 2011 (C M Jewell & Associates, 2011). Information from this review was used to support the development of a business case for a trial of MAR in the Orange area (MWH, 2011b).
This project proposes a trial of MAR in the Orange area over a five year period. The purpose of the trial is to (MWH, 2011b): • increase the knowledge of using managed aquifer recharge and recovery schemes within different rock types within a fractured rock aquifer; and • provide an option to increase the city’s raw water storage capacity.
The operation of MAR would be trialled in seven bores in the Orange area. Five bores would be established in fractured rocks of Orange tertiary basalt just south of Orange. Two established bores, one at the Orange City Showground and one at the Clifton Grove shearing shed would be used to show MAR operation in other parent rock types. The operation of this trial over five years would provide sufficient knowledge to determine the capabilities, and costs of using MAR in fractured rock aquifers in the Orange area to store and retrieve up to 20 GL of water.
The business case for the trial established the key project parameters (including budget) and identified key project stakeholders.
The estimated capital cost of the trial is $2.113 million. The trial is included in Council’s BAU scenario and the cost is included in Council’s capital works program in 2013/2014.
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As noted above, MAR requires additional water sources to recharge the aquifer. Secure yield modelling was undertaken to examine the impact of MAR that provided an additional 22 GL of aquifer storage. Additional water sources in this analysis included stormwater harvesting and input from the Macquarie River. This work was undertaken in June and July 2011 and was based on the preliminary Macquarie River data that has subsequently been revised. At this time however it was determined that the MAR schemes could increase secure yield by around 1,300 ML/year.
It should be noted the secure yield modelling had many assumptions about how a MAR scheme would operate including: • the total storage available; • the recovery rate (i.e. how much water can be extracted compared to how much is put in); • the daily input and extraction rates; and • when extraction would be triggered and the relationship between the aquifer storage and surface storages.
Information gained from the MAR trial would be used to improve the modelling assumptions.
3.5.4 LONG LIST RECOMMENDATIONS
The following long list of groundwater options can be derived from the above assessment: • GW1: existing bores (included in BAU); • GW2: bores in the Orange basalt zone; • GW3: MAR trial (included in BAU); and • GW4: bores in North Orange.
Further consideration and short listing of options is presented in Section 4.
3.6 TREATED EFFLUENT
3.6.1 DESCRIPTION
Orange City Council has two sewage treatment plants (STPs): the Orange STP and the Spring Hill STP. The Orange STP services the city of Orange, and the Spring Hill STP services Spring Hill and Lucknow. All urban areas are serviced.
The majority of Orange STP treated effluent is reused under agreement by Cadia Holdings in their Cadia Valley Operations. The balance is discharged under licence to Blackmans Swamp Creek. All of Spring Hill STP effluent is reused for the irrigation of 11 ha of land at a neighbouring farm and the Orange airport.
3.6.2 VOLUME
Technical Note 3 presents an assessment of future water demands for Orange and the villages of Spring Hill and Lucknow which were derived using the DEUS Demand Management Decision Support System (DSS) version S1.1 (DEUS, 2006). The DSS model includes an estimate of the forecast effluent production based on the potable water demand and data relating to the split between internal and external water use. The DSS model calculates the: • STP annual inflow; • Average Dry Weather Flow (ADWF); and • Wet Weather Flow (WWF).
Results from this modelling are discussed below for the two STPs.
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3.6.2.1 Orange STP
Effluent Production
The forecast water demand and effluent generation for Orange was based on two growth projections: a medium rate of 0.8% pa; and a high rate of 1.1% pa. Forecast trends in annual effluent production under medium and high growth rates for the BAU scenario are shown in Figure 40 and Figure 41 respectively.
Baseline Forecast Medium Demand Management = BAU High Demand Management
6000
IWCM 30 year planning period
5000
4000
3000 STP STP Inflow ((ML/year)
2000
1000
0 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060 Year
Figure 40: Forecast total annual effluent production – city of Orange, medium growth
Baseline Forecast Medium Demand Management = BAU High Demand Management
6000
IWCM 30 year planning period
5000
4000
3000 STP STP Inflow ((ML/year)
2000
1000
0 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060 Year
Figure 41: Forecast total annual effluent production – city of Orange, high growth
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The Orange STP has a capacity of 60,000 EP or an approximate ADWF of 14 ML/day. The STP has capacity to provide full treatment up to approximately 43.2 ML/day (500 L/s). The existing STP therefore has sufficient capacity to meet the forecast effluent production over the next 50 years under the BAU scenario.
Effluent Availability
Cadia Holdings Pty Limited undertake mining operations in or around Cadia (Cadia Valley Operations – CVO). Cadia Holdings is under contract with Orange City Council to receive recycled water from the Orange STP. This agreement gives CVO access to a minimum 10 ML/day with the ability to take up to 13 ML/day (the capacity of the transfer system) if the excess above 10 ML/day is not required by Council. The agreement provides CVO with access to at least 3,650 ML/year of treated effluent.
The water supply agreement started in December 1997 and was set to continue for the life of the mine. A recently approved expansion of mining operations has extended the life of the mine, and the need for the supply of treated effluent, until at least 2030. OCC and Cadia Holdings are currently negotiating a new water supply agreement including possibly placing a financial value on the recycled water.
This agreement reuses the majority of the treated effluent produced at the Orange STP. Data for the period 2001 to 2011 is provided in Table 3.45 and shows an average of 72% of the effluent produced over this period was transferred to CVO. The annual transfer ranged from 28% to 94% and averaged 8.2 ML/day over this period. The low transfer year corresponded with a very high rainfall period and on site water sources for the mine were at or near capacity which reduced the need for effluent.
During large wet weather flows to the Orange STP the transfer to CVO is closed down, because effluent that bypasses the primary and secondary treatment contaminates the treated effluent in the chlorination tank (MWH, 2007). The only other time the transfer to CVO is closed down is when the mine has a shutdown period or the effluent cannot be utilised. Shutdown happens every six months for a few days.
The annual STP inflow from an annual water production of 5,400 ML/year is 3,481 ML/year (refer to Technical Note 3). This indicates that with the reduced water production there is less effluent available and it is unlikely that CVO will transfer 10 ML/day. Modelling was used to estimate the average transfer over the next 20 years (to 2030) based on the forecast water production for the BAU scenario. This assessment determined an average transfer of 9.5 ML/day (3,467 ML/year).
The availability of spare treated effluent after meeting an average supply of 9.5 ML/day is indicated on Figure 42 for the BAU scenario. It should be noted that there are some treated effluent discharges above the volumes shown due to bypass events or mine shutdown that are not accounted for in the modelling. However, the modelling indicates that there is unlikely to be any consistent quantities of spare treated effluent until about 2025 under the medium growth rate and 2020 under the high growth rate.
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Table 3.45 – Annual effluent transfer to CVO
STP Inflow Export to CVO Year % Reuse ML/year ML/year
2001-2002 4,866 3,104 64%
2002-2003 4,011 3,033 76%
2003-2004 4,652 3,362 72%
2004-2005 4,445 3,360 76%
2005-2006 4,197 3,121 74%
2006-2007 2,847 2,665 94%
2007-2008 3,629 3,367 93%
2008-2009 3,565 3,063 86%
2009-2010 3,310 3,026 91%
2010-2011 5,924 1,674 28%
Ten year totals 41,446 29,775 72%
BAU effluent production medium growth BAU effluent production high growth
Spare effluent medium growth Spare effluent high growth
6000
IWCM 30 year planning period 5000
4000
3000 STP STP Inflow ((ML/year)
2000
1000
0 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060 Year
Figure 42: BAU treated effluent production and availability
As noted above, Council and Cadia Holdings Pty Limited are currently negotiating a new water supply agreement given that the mine has recently gained approval to operate through to 2030. Cadia Holdings Pty Limited is viewed by Council as a customer using one of the available water sources.
Construction and operation of the effluent transfer system has not cost the Orange community anything as these costs are fully met by Cadia Holdings under the terms of the agreement. The water supply agreement benefits Council by saving an average of around $50,000 per year in load based licence fees that would be incurred if the effluent was discharged to Blackmans Swamp Creek.
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It is Council’s intent that the water supply agreement continues into the future (subject to the current negotiations) as it provides a substantial and secure supply for the mine operations which are seen as an important component of the Orange economy. Therefore, apart from the minor amounts that bypass during wet weather and STP flow that CVO do not take, there is only a small amount of treated effluent available for at least the next 20 years. The small and inconsistent volume makes it difficult to justify installing (for example) treatment systems to allow some form of reuse. These types of options become more viable once the full treated effluent stream is available.
Despite this, one option considered for the effluent stream was Indirect Potable Reuse (IPR). This was done on the assumption that the effluent would be available (i.e. the water supply agreement was terminated) so that this potential water supply technology could be compared to other options.
Other options considered examined minor uses of the treated effluent for alternate water supplies or supplementing environmental flow in Blackmans Swamp Creek.
3.6.2.2 Spring Hill STP
Effluent Production
The forecast water demand and effluent generation for Spring Hill and Lucknow was based on two growth projections: zero growth; and a high rate of 0.8% pa.
Effluent production results for the BAU demand management scenario at 10 year intervals are summarised in Table 3.46.
The DSS model results show that annual effluent production is forecast to range between 28 and 41 ML/year with ADWF ranging between 0.06 to 0.09 ML/day for the BAU scenario.
The Spring Hill STP has a capacity of 1,000 EP or an approximate ADWF of 0.28 ML/day. The STP has capacity to provide full treatment up to approximately 2.3 ML/day. The existing STP therefore has sufficient capacity to meet the forecast effluent production over the next 50 years.
Table 3.46 – Spring Hill and Lucknow effluent production forecast Scenario Measure Growth 2010 2020 2030 2040 2050 2060 BAU Annual inflow Zero 34 30 28 28 28 28 (ML/year) 0.8% 34 32 33 35 38 41 ADWF (ML/day) Zero 0.08 0.07 0.06 0.06 0.06 0.06 0.8% 0.08 0.07 0.07 0.08 0.08 0.09 WWF (ML/day) Zero 0.23 0.22 0.22 0.21 0.21 0.21 0.8% 0.23 0.24 0.25 0.27 0.29 0.32
Treated effluent from the Spring Hill STP is reused across an 11 hectare irrigation area. The average annual application rate remains less than 4 ML/ha/year which is low and considered to be sustainable. The STP produces only a modest amount of treated effluent and the current management is considered to be the most appropriate use of the treated effluent.
No other options for the use of the treated effluent from the Spring Hill STP are considered in this review.
3.6.3 INDIRECT POTABLE REUSE 3.6.3.1 Description
An option for future water supply is to develop an indirect potable reuse (IPR) scheme. This would entail advanced treatment of the municipal wastewater to a very high standard with this reclaimed water then being transferred to Suma Park Reservoir where it would mix with raw water. The advanced treatment stage must address both the acute and chronic risks associated with introducing the reclaimed water into a drinking water supply.
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As noted above, the consideration of this option is based on the assumption that the current water supply agreement with CVO is terminated (refer to Section 3.6.2.1).
Council commissioned a report in 2009 that examined and scoped the treatment systems required for various water reuse schemes including IPR (IBL Solutions, 2009). This report was updated in 2011 focusing on the options for IPR (IBL Solutions, 2011). Both reports are attached as Appendix B.
A review of technology identified three possible treatment systems for an IPR scheme: • Non-membrane – these systems use coagulation, filtration and disinfection; • Membrane system without brine treatment – these systems use micro and reverse osmosis filtration and disinfection. The reject from the filtration process is discharged to the environment; and • Membrane systems with brine treatment (zero liquid discharge system) – these systems treat the brine reject from the filtration process so that there is not discharge to the environment.
Further detail of these systems is provided in Appendix B.
The volume of reclaimed water produced by the non-membrane plant is greater compared to the membrane systems due to the concentrate produced from the reverse osmosis (RO) in the membrane systems. The concentrate from RO, which can amount to 15% to 25% of the flow to the RO unit, requires disposal. It is generally disposed of to the ocean in the case of coastal cities while evaporation basins, deep well injection or concentration followed by crystallisation are considered for inland locations.
Two IRP schemes were assessed: • E1: non-membrane IPR plant treating 10 ML/day; and • E2: membrane IPR plant with brine treatment treating 10 ML/day.
3.6.3.2 Non-membrane IPR Scheme
Description
The typical treatment process for a non-membrane plant is shown in Figure 43. These systems use coagulation, filtration and disinfection to remove pathogens and organics. The surface water reservoir in this treatment train would be Suma Park Reservoir.
Source: IBL Solutions (2009)
Figure 43: IPR non-membrane treatment train
Potential Secure Yield
A non-membrane system treating 10 ML/day would deliver about 9.4 ML/day to Suma Park Reservoir. As this is a constant inflow, it would equate to an equivalent increase in secure yield. Therefore the secure yield provided by the non-membrane IPR system is around 3,400 ML/year.
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Preliminary Capital and Operating Costs
The works required for Option E1 would include: • the IPR treatment plant ($22 million) (refer to Appendix B); and • a pump station and pipeline system to transfer treated effluent to Suma Park Reservoir ($2.86 million).
The annual operating costs for the membrane plant with zero liquid discharge are $4.4 million/year (refer to Appendix B). Additional operating costs are required for the effluent transfer system estimated at $418,000/year.
Summary
Table 3.48 summarises the option of using a non-membrane IPR scheme as part of the water supply system.
Table 3.47 – Summary of Option E1: Non-membrane IPR scheme Measure Result Capital cost, $ $24,860,000 Operating cost, $/year $4,818,000 NPV – capital cost, ($2010) $25,657,000 NPV – operating cost, ($2010) $66,322,000 Potential increase in secure yield, ML/year 3,400 Capital costs, $/ML increase in secure yield $511 Operating costs, $/ML increase in secure yield $1,321 Total cost of secure yield supplied, $/ML increase in secure yield $1,832 Change in TRB if adopted $261 per assessment
Greenhouse Gas Emissions (operating power only) 2.40 tonnes CO2e/ML Issues to consider • Effluent not currently available due to contract with Cadia Mines – unlikely before 2031 • Water quality risk assessment • Non-membrane plant unlikely to be accepted by NOW • Approvals/licensing process • Community acceptance • Additional Council resources required due to higher level technology Likely timeframe to complete 5 to 8 years
3.6.3.3 Membrane IPR Scheme
Description
The third IPR treatment system above (membrane plus brine treatment) includes a zero liquid discharge treatment system to treat the concentrate from the RO unit. This would be required for Orange as there are no opportunities for deep well injection and evaporation systems would be very marginal due to climate.
The treatment process for a membrane plant is shown in Figure 44. The NSW Office of Water advised that they are unlikely to accept a non-membrane system if IPR was being considered as a long term water security option due to public health risks. Therefore Option E2 (membrane plant) would be the preferred IPR option.
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Source: IBL Solutions (2009) Figure 44: IPR membrane treatment train
Potential Secure Yield
A membrane system treating 10 ML/day would deliver about 9.1 ML/day to Suma Park Reservoir. As this is a constant inflow, it would equate to an equivalent increase in secure yield. Therefore the secure yield provided by the membrane IPR system is around 3,300 ML/year.
Preliminary Capital and Operating Costs
The works required for Option E2 would include: • the IPR treatment plant ($55 million) (refer to Appendix B); and • a pump station and pipeline system to transfer treated effluent to Suma Park Reservoir ($2.86 million).
The annual operating costs for the membrane plant with zero liquid discharge are $3.9 million/year (refer to Appendix B). Additional operating costs are required for the effluent transfer system estimated at $402,000/year.
Summary
Table 3.48 summarises the option of using a membrane IPR scheme as part of the water supply system.
Table 3.48 – Summary of Option E2: Membrane IPR scheme
Measure Result
Capital cost, $ $57,860,000
Operating cost, $/year $4,302,000
NPV – capital cost, ($2010) $54,212,000
NPV – operating cost, ($2010) $51,441,000
Potential increase in secure yield, ML/year 3,300
Capital costs, $/ML increase in secure yield $1,112
Operating costs, $/ML increase in secure yield $1,056
Total cost of secure yield supplied, $/ML increase in secure yield $2,168
Change in TRB if adopted $318 per assessment
Greenhouse Gas Emissions (operating power only) 2.40 tonnes CO2e/ML
Issues to consider • Effluent not currently available due to contract with Cadia Mines – unlikely before 2031 • Water quality risk assessment • Approvals/licensing process • Community acceptance • Additional Council resources required due to higher level technology
Likely timeframe to complete 5 to 8 years
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3.6.3.4 Supplementing flow in Blackmans Swamp Creek
It was suggested at PRG Meeting 3 that treated effluent could be used to supplement flow in Blackmans Swamp Creek/Summer Hill Creek to offset the potential impacts of additional stormwater harvesting. This option in itself does not provide an additional water source or increase the secure yield unless it enables mores harvesting to occur. It may assist getting approval/licensing for current or future harvesting stages.
Council’s BAU scenario includes Stage 2 of the Blackmans Swamp creek stormwater harvesting scheme. Council would only pursue the second stage once full licensing of Stage 1 has been granted and the water quality approval process outlined by the NSW Office of Water has been successfully completed. This is likely to be a 3 to 5 year process.
Stage 2 harvesting is estimated to increase the secure yield by 900 ML/year and increases the average annual extraction from Blackmans Swamp Creek from 8% to 17%. This additional volume could be compensated by using some treated effluent; however doing so would not change the secure yield provided by the second stage of harvesting. An average daily discharge of treated effluent of around 2.4 ML/day would be required to compensate the increased extraction by going from Stage 1 to Stage 2 of harvesting.
Some increase in harvest capacity could be gained using the Stage 2 infrastructure by increasing pump capacities and reducing the base flow released from the harvest weir during harvest events4. This could potentially add 300 to 400 ML/year in secure yield and would increase the average annual extraction from Blackmans Swamp Creek to around 21%. To fully compensate this extraction volume (i.e. the increased extraction going from Stage 1 to the enhanced Stage 2) would require an average treated effluent release of 3.5 ML/day; or 1.1 ML/day to compensate the extra extraction compared to the current Stage 2.
Conceptual systems to further increase the harvesting capacity (i.e. Stage 3 and maximum harvesting) are described in Section 3.3. These rely on increasing the volume of on-line storage to increase the capture of runoff during storm events. As discussed in that section, successfully obtaining approval and licensing for these works is unlikely. Therefore it is considered that stormwater harvesting on Blackmans Swamp Creek will be limited to Stage 2. These works are included in Council’s BAU scenario and do not rely on compensatory effluent discharge.
The conclusion from this is that the amount of stormwater harvesting that can occur on Blackmans Swamp Creek is limited more by engineering and licensing constraints than creek flow regime constraints. Using treated effluent to compensate harvesting would not provide an additional water source or significantly increase the secure yield from stormwater harvesting.
Treated effluent could be used to supplement creek flow for environmental reasons. This is being considered as part of the environmental flow study currently underway.
Other factors to consider for this option are discussed below: • Treated effluent is currently supplied under agreement to Cadia Holdings Pty Limited. Using a portion of the effluent flow to supplement creek flow would require changes to this agreement. This is not insurmountable, but it is very likely that Cadia Holdings would wish to retain the current supply agreement; • The average daily volume of treated effluent produced at the Orange STP is lower now than it has been in the past due to lower water consumption. Forecasts of water demand indicate that this is not likely to change significantly over the next 10 years as demand is expected to remain at or around the same levels. Therefore a high proportion of the treated effluent will be reused under the existing water supply agreement with Cadia Holdings Pty Limited. Modelling has indicated that apart from the minor amounts that bypass during wet weather and STP flow that Cadia Holdings Pty Limited do not take, there is only a small amount of treated effluent available for at least the next 20 years;
4 For this analysis it was assumed the low flow pump would increase to 100 L/s, PS1 would increase to 600 L/s and the base flow released during harvesting would reduce to 2 ML/day.
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• Discharge of treated effluent would incur load based licence fees; • Relying only on increased stormwater harvesting to meet forecast water demands removes diversity from the water supply system. Council is seeking a diverse system to improve reliability and to lessen the impact on one particular water source; and • It would not be practicable to hold the effluent volume for release during harvesting events as the volume of storage required would be large. The most practicable means would be a constant daily release to compensate the average annual volume removed through harvesting. This would provide a permanent low flow in the creek system. Whether this is an appropriate way to manage the creek system is unknown at this stage. Council has commissioned an environmental flow study that will examine these aspects.
3.6.3.5 Dual Reticulation
Dual Water Supply Area
In 2002 Orange City Council investigated the feasibility of providing a dual water supply system for the Ploughmans Valley and North Orange (PVNO) development areas; a scheme that would ultimately supply non-potable water to 4,500 homes in the north and west of the city. The original intent of the system was to supply treated municipal sewage effluent to residential properties for toilet flushing and outdoor use. The system has been partially constructed and, by the start of 2011, around 1,000 properties had been connected. Connection to the non-potable alternate water supply for toilet and outdoor use was deemed by the Department of Planning (DoP) to satisfy the criteria as a reticulated alternative water supply under BASIX.
The system is currently is charged with potable water as treated effluent is not available due to the water supply agreement with Cadia Holdings. As discussed above, there is unlikely to be an adequate supply of treated effluent for some time under this agreement.
Council undertook a review of this system in early 2011 and considered a range of alternate water sources for the dual water system to ensure ongoing compliance with BASIX requirements in the PVNO area (Geolyse, 2011). These options included: • ensuring development of low-water use gardens; • retro-fitting rainwater tanks to houses; • use of raw water from Suma Park Reservoir to supply the dual water system; • use of treated effluent to supply the dual water system; and • using harvested stormwater to supply the dual water system – five (5) options utilising harvested stormwater were considered.
It was recommended from this study that the system be supplied with harvested stormwater. This was approved by the DoP and the required capital works are underway and scheduled for completion in the last quarter of 2012.
Therefore, treated effluent is unlikely to be required for the dual water supply system.
Parks and Gardens
An option raised during consultation was to supply treated effluent as a non-potable source of water for parks and gardens. Issues to be considered for this option are: • It is a relatively low volume (estimated to be less than 100 ML/year); • There would be very high reticulation costs as most parks and gardens are located within established areas of the city. This issue was highlighted in the review undertaken by IBL Solutions (2009); • A very high level of treatment would be required to minimise public health risks as most parks and gardens have unrestricted public access. The option was included on the long list.
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3.6.3.6 Storm Flow Storage at Orange STP
Orange City Council commissioned a feasibility study into the provision of storm flow storage at the Orange STP (Hunter Water Australia, 2006). The aim of this project was to investigate the feasibility of constructing structures to store some or all of the stormwater affected high flows experienced at the STP which are normally discharged to Blackmans Swamp Creek partially treated. These storm bypass flows could then be returned to the treatment process when the high flows have abated.
The main aim of providing storage was to improve the ability of the system to meet recycled water demand which at the time of the study included the dual reticulation area (PVNO area described above) and the CVO water supply agreement. As noted above, the use of treated effluent in the dual reticulation system is no longer proposed. However the greatest demand for recycled water in the assessment was the water supply agreement with CVO.
The study examined three options: • upstream storage – storage constructed upstream of the STP that would collect storm bypass flows and balance high flows into the plant; • downstream storage – storage constructed downstream of the STP that would collect excess treated effluent (i.e. the excess flow above what the recycling system could take) that would otherwise discharge to the creek; and • a combination of upstream and downstream storage systems.
The preferred options that met minimum design criteria were: • downstream storage (20 ML or larger); or • combined upstream storage (25 ML or larger) and downstream storage (20 ML or larger).
Modelling was used to determine the volume of effluent discharged to Blackmans Swamp Creek due to lack of storage. Comparing the results for the existing system (minimal storage) with those for various sizes of upstream and downstream storages provides an indication of how much effluent could be recovered using this system. These results are summarised in Table 3.49 and show that between 54 and 194 ML/year of effluent could be recovered through a storage system. The downstream system performed better than the combined upstream and downstream system in terms of reducing discharge to Blackmans Swamp Creek.
Table 3.49 – Orange STP storm flow storage
Case Measure 2006 2016 2026
Existing Effluent discharged due to lack of storage, ML/year 639 721 788
Effluent recovered, ML/year - - -
20 ML downstream storage Effluent discharged due to lack of storage, ML/year 519 597 651
Effluent recovered, ML/year 120 124 137
35 ML downstream storage Effluent discharged due to lack of storage, ML/year 484 561 612
Effluent recovered, ML/year 155 160 176
50 ML downstream storage Effluent discharged due to lack of storage, ML/year 466 542 594
Effluent recovered, ML/year 173 179 194
25 ML upstream storage Effluent discharged due to lack of storage, ML/year 585 645 731 20 ML downstream storage Effluent recovered, ML/year 54 76 57
Source: Hunter Water Australia (2006) Tables 4.2, 4.8 and 4.10
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Several aspects have changed since this study: • The area nominated for the location of the downstream storage is now occupied by the 230 ML stormwater holding pond. Therefore a different location would need to be used; • STP inflow has dramatically reduced due to lower water consumption – caused not only by restrictions but by changes in water consumption behaviour. The modelling used in the report adopted an average inflow of 12.14 ML/day in 2006 increasing to 14.56 ML/day in 2026. Modelling for the IWCM Evaluation Study (refer to Technical Note 3) shows an average inflow of 9.5 ML/day in 2010 increasing to around 11 ML/day in 2030. Analysis discussed above shows that the majority of this will be transferred to CVO; and • It is no longer proposed to use treated effluent in the PVNO dual water supply scheme.
Despite these changes, data from the storm flow study was used to conceptualise a system that could capture potential excess flow which would then be treated and used to supplement the water supply system. Adopting the best performing system from the analysis (50 ML downstream storage) the data indicates that it could recover around 170 to 190 ML/year of effluent. Based on these result, if this system was constructed and the recovered effluent was treated and used to supplement the water supply, it would equate to a secure yield of around 150 ML/year.
Preliminary capital cost for this scheme is estimated at $3.67 million which is summarised in Table 3.50.
Table 3.50 – STP storm flow capture – preliminary cost estimates
Item Cost ($’000)
Preliminaries $150
Pond $750
Pumps, controls and pipework $400
Treatment system $1,100
Power and controls $225
Approvals $200
Survey, investigation, design and project management (15%) $424
Contingency (15%) $424
Total $3,673
Annual operating costs based on an average annual volume of 150 ML/year are $184,000/year as follows: • Power $9,000/year • Treatment $150,000/year • Maintenance $25,000/year
Table 3.51 summarises the option of using a storm flow recovery scheme at the Orange STP as part of the water supply system.
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Table 3.51 – Summary of Option E5: STP storm flow recovery scheme
Measure Result
Capital cost, $ $3,673,000
Operating cost, $/year $184,000
NPV – capital cost, ($2010) $3,673,000
NPV – operating cost, ($2010) $2,720,000
Potential increase in secure yield, ML/year 150
Capital costs, $/ML increase in secure yield $1,658
Operating costs, $/ML increase in secure yield $1,228
Total cost of secure yield supplied, $/ML increase in secure yield $2,886
Change in TRB if adopted $18 per assessment
Greenhouse Gas Emissions (operating power only) 0.14 tonnes CO2e/ML
Issues to consider • Effluent flow reduced – volumes unlikely to be available • Water quality risk assessment • Approvals/licensing process • Additional Council resources required due to higher level technology
Likely timeframe to complete 5 to 8 years
3.6.3.7 Decentralised STPs with Local Reuse
It was suggested at Project Reference Group meeting 3 that consideration could be given to decentralised STPs with local reuse. These would be located in new development areas, for example in the south and north of the city.
This option is a longer term solution and does not provide any short term benefit or improvement in secure yield as the areas are not developed. It is also noted that the existing Orange STP has sufficient capacity to meet forecast loads through for at least the next 30 years. Constructing and operating decentralised STPs would represent underutilisation of an existing asset.
Water quality risks would also need to be addressed.
3.6.3.8 Greywater Reuse
Household greywater reuse was suggested at Project Reference Group meeting 3. This would involve household capturing, treating and reusing wastewater from the laundry and shower/bath.
A typical household water use profile for Orange was developed as part of the assessment of alternative water supply options for the PVNO dual water supply area (Geolyse, 2011). This is shown in Figure 45.
This shows an average consumption of around 92 kL/year for the laundry and bath/shower, and an outside use of 82 kL/year. It the greywater was used to replace the outside use, the potential potable water saving could be around 82 kL/year per household.
Assuming 30% of existing households adopt greywater reuse, this would equate to an annual saving of around 350 ML/year.
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Figure 45: Average household water use, kL/year
There is some potential for greywater reuse to reduce potable water demand. It does however rely on households installing and managing an appropriate treatment system, and would rely on a reasonable uptake by the community to achieve any substantial benefit.
The need to reduce effluent loads on existing infrastructure is not a driver for this option as the existing Orange STP has sufficient capacity to meet forecast loads through for at least the next 30 years.
3.6.4 LONG LIST RECOMMENDATIONS
The following long list of effluent options can be derived from the above assessment: • E1: non-membrane IPR scheme; • E2: membrane IPR scheme; • E3: supplementing flow in Blackmans Swamp Creek; • E4: dual water to parks and gardens; • E5: storm flow storage at Orange STP; • E6: decentralised STPs with local reuse; and • E7: greywater reuse.
Further consideration and short listing of options is presented in Section 4.
3.7 REGIONAL WATER RESOURCES
3.7.1 CENTROC STUDY
Central NSW Regional Organisation of Councils (Centroc) undertook a Water Security Study to investigate and recommend solutions to improve water security across 17 LGA’s (MWH, 2009). The study included an audit of existing bulk water supply infrastructure (Component 1) and an assessment of options to improve water supply security (Component 2).
Water demand forecasts were developed for each town for the next 50 years (until 2059). The forecasts took into account projected population growth, surface water and groundwater resources, climate sequence and climate change. The study identified that 29 towns were at risk, and required substantial water security improvements, Orange being one of these towns at risk.
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It was determined that an integrated program of water conservation and demand management measures, coupled with new and upgraded water supply and storage infrastructure was required. The recommended region-wide town water security strategy is described as 2a: Lake Rowlands Regional Network + Local Options + Cadia Hill (MWH, 2009, p45). This strategy recommended the following infrastructure: • Lake Rowland augmentation to a capacity of 26,500 ML; • Lake Rowlands to Millthorpe pipeline (CTW Truck Mains D and F duplication); • CTW to Orange pipeline via Millthorpe; • Lake Rowlands to Gooloogong pipeline (CTW Trunk Mains P and C duplication); • Gooloogong to Forbes pipeline (including connection to Parkes); • Woodstock to Cowra pipeline; • Orang to Molong Creek Dam pipeline (lower priority action resulting from the level of surety around the security of Molong. There is an existing pipeline from Molong Creek Dam into which this new pipeline would connect); • New minor storage and water treatment facilities at Cumnock; • New minor storage and water treatment facilities at Yeoval; • New minor storage at Condobolin (off-stream from Lachlan river); • New pipeline replacing the existing channel and minor storage at Lake Cargelligo; • Burrendong to Wellington pipeline; • Chifley to Bathurst pipeline; • Chifley to Oberon pipeline; and • Belubula Creek to Cadia Hill pipeline (already available).
The above infrastructure would be combined with continued best practice management across the region.
The study also recommended contingency actions for emergency situations which included: • The emergency development of the groundwater resources of Forbes, Wellington, Condobolin and Lake Cargelligo; and • The construction of a pipeline connection between Orange and the Macquarie River.
3.7.2 LAKE ROWLANDS 3.7.2.1 Description
In terms of infrastructure, an augmented Lake Rowlands was the key to the Centroc recommended region-wide town water security strategy. In the immediate term, there is insufficient capacity in Lake Rowlands for it to play a significant regional water security role. Enlarging the dam to a capacity of 26,500 ML would increase the system secure yield and provide additional water to the regional network.
Coupled with the augmentation of Lake Rowlands was a series of pipeline connections to distribute water to Centroc centres. A pipeline to Orange was one of these proposed connections (refer to Figure 46).
The need to enlarge Lake Rowlands before adequate water could be available means that this is a longer term project (10 to 15 years).
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Figure 46: Potential pipeline from Lake Rowlands to Orange
3.7.2.2 Potential Secure Yield
Since the Centroc study, further secure yield assessment was undertaken for Lake Rowlands. This estimate indicated that under a climate change scenario the secure yield from Lake Rowlands is 4,600 ML/year5. This is much lower than the previous assessment of 8,000 ML/year.
5 In early 2012 the Minister for Primary Industries instructed the New South Wales Office of Water (NOW) to undertake an independent review of the secure yield analysis of the augmented Lake Rowlands on the 5/10/10 rule and considering the Federation Drought. The Lake Rowlands yield study was completed in November 2011. This study indicates that under a climate change scenario the secure yield from Lake Rowlands is 3,150 ML/year, which is lower than the previous estimate of 4,600 ML/year. This revised assessment indicates that there is unlikely to be significant “spare” secure yield to supply Orange, particularly when climate change is considered. Furthermore, the Draft Water Sharing Plan for Lachlan Unregulated and Alluvial Water Sources places limitations on water access entitlements. This data was not available at the time of undertaking the comparison of options for the IWCM Evaluation Study. Therefore the assessment presented in this report is based on the previous secure yield of 4,600 ML/year and assumptions derived from this value.
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With the yield of the augmented Lake Rowlands significantly reduced it is difficult to determine the likely share of water that could be directed to Orange. For the purpose of this assessment it is assumed that Orange will be able to access 972 ML/year from Lake Rowlands as follows: • a Lake Rowlands secure yield of 4,600 ML/year3; • Central Tablelands Water baseline demand of 2,750 ML/year, of which 400 ML/year is supplied by bores; and • there is a commitment to supply Cowra with 1,278 ML/year in drought periods, which would reduce the amount available during the critical drought in terms of secure yield modelling.
3.7.2.3 Preliminary Capital and Operating Costs
It terms of water supply, it is estimated that Orange may be able to secure around 972 ML/year. This represents 21% of the system secure yield and forms the basis of the capital cost apportionment for Orange as the dam augmentation would be a joint initiative. Therefore the capital costs assume: • Orange contributes 21% of the dam capital costs (total estimated cost $150 million); and • Orange pays for the pipeline and transfer system (total estimate cost $53 million).
This is a total capital cost of $84.5 million.
Operating costs assume a 300 kW pump system transferring and average of 3.24 ML/day power and maintenance estimated as follows (based on an average annual transfer of 972 ML/year): • Power $376,000 • Maintenance $200,000
3.7.2.4 Summary
Table 3.52 summarises the option of using a pipeline from an augmented Lake Rowlands as part of the water supply system.
Table 3.52 – Summary of Option R1: Pipeline from augmented Lake Rowlands
Measure Result
Capital cost, $ $84,500,000
Operating cost, $/year $576,000
NPV – capital cost, ($2010) $73,918,000
NPV – operating cost, ($2010) $6,420,000
Potential increase in secure yield, ML/year 972
Capital costs, $/ML increase in secure yield $5,150
Operating costs, $/ML increase in secure yield $447
Total cost of secure yield supplied, $/ML increase in secure yield $5,597
Change in TRB if adopted $246 per assessment
Greenhouse Gas Emissions (operating power only) 1.72 tonnes CO2e/ML
Issues to consider • Revised secure yield estimates may indicate sufficient water is not available to make this a viable option • Environmental approval process for a new dam could be protracted • Management of regional water scheme
Likely timeframe to complete 10 to 15 years
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3.7.3 MOLONG CREEK DAM
Molong Creek Dam was identified as a potential water source in the Centroc regional water security study (MWH, 2009). The option included augmenting the dam and providing a pipeline connection to Orange. Cabonne Council estimates that raising the existing dam wall by 1.0 m doubles the current dam capacity (MWH, 2009).
The net present value of the capital costs for the dam augmentation and pipeline to Orange were estimated in the Centroc study as $18 million (MWH, 2009).
The current yield of this dam is 300 ML/year and after augmentation the secure yield can be increased to around 450 ML/year. Assuming a climate change reduction of around 25% (based on the climate change pilot study, Samra and Cloke (2010)), this secure yield reduces to 337 ML/year.
The baseline demand forecast for Molong when extrapolated sees only 17 ML/year available in 2060. This would appear not to be a viable source of water for the city.
3.7.4 LONG LIST RECOMMENDATIONS
The following long list of regional options can be derived from the above assessment: • R1: pipeline from an augmented Lake Rowlands (continued support to Centroc for this project is included in BAU); and • R2: pipeline from Molong Creek Dam.
Further consideration and short listing of options is presented in Section 4.
3.8 OTHER
3.8.1 LUCKNOW MINE – REFORM SHAFT
The Reform shaft is a disused mineshaft, with an estimated depth of over 100 m and a headframe still intact. It is located in the town of Lucknow, approximately nine kilometres south-east of Orange. The mine contains groundwater which during operation of the mine would have been managed through pumping.
Orange City Council has commissioned two studies examining the use of groundwater from the mine: • Groundwater sampling, Reform shaft, Lucknow, New South Wales (C M Jewell & Associates, 2004) – this study presents results of groundwater quality sampling and analysis; and • Overview of potential hydrogeological and geotechnical issues relating to the extraction of water from the former Lucknow Mine, New South Wales (C M Jewell & Associates, 2009).
Quality
Two water samples were collected from the mine shaft at depths of six and eight metres. Analyses of the samples were compared to threshold analyte concentration levels as specified by the Australian Drinking Water Guidelines. The results show that arsenic concentrations within the water samples exceed the recommended maximum health-based level which is of concern as arsenic concentrations above this guideline value can be toxic to humans and animals. Arsenic can be removed from drinking water supplies using conventional coagulation processes.
Results also indicated that that manganese concentration exceeded the aesthetic-based guideline. Manganese concentrations above this guideline value can cause taste and other problems.
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Quantity
The 2009 report presented an overview of some of the potential hydrogeological and geotechnical issues relating to dewatering of the mine.
The groundwater resource intercepted by the shaft is interpreted as being a ‘fractured rock’ aquifer type. Fractured rock aquifers can have high yields. However, the long-term yield is controlled by the continuity and extent of the fracture system. In natural fractured systems, storage is often low, but where mine voids or stoped areas are present, these may provide significant storage.
It was concluded that that useable quantities of relatively good quality water may be able to be abstracted from the mine. Dewatering of the mine has shown that it may have a sustainable yield of about 2 ML per week (around 100 ML/year) – which equates to a borehole with a yield of about 3.3 L/s being continuously pumped for the same duration.
The report discussed potential impacts including: • disturbance of groundwater equilibrium, lowering of water table and redirection of flow; • reduced borehole yields and drying of boreholes; • groundwater provides hydraulic support to natural and artificial structures that exist from when the mine was active. Removal of groundwater may result in collapse; • geochemical changes are likely as rock surfaces and minerals are again brought into contact with atmosphere – this may affect water quality; • the connectivity between surface and groundwater in the area is expected to be high, so some loss of base flow in Summer Hill Creek is likely - so groundwater extraction from the Reform shaft may impact on Suma Park Reservoir’s water resources; and • subsidence including opening of new fractures and damage to property.
Based on these concerns, it is likely that a comprehensive hydrogeological and geotechnical investigation would be required prior to an abstraction licence being granted, whilst ongoing monitoring, administration and reporting are also expected to be required.
Lucknow Gold, who has exploration leases for the Lucknow area, may also have a claim on the water.
3.8.2 BROWNS CREEK MINE 3.8.2.1 Overview
The Department of Commerce completed a desktop study on the feasibility of transferring water from the abandoned Browns Creek Mine at Blayney for Orange drinking water needs (Department of Commerce, 2008). This study considered transferring water from the mine to Orange for both short- term and long-term water security options. In the short term, mine water would be used as an emergency supply whilst in the long term the transfer system would possibly integrate with other future augmentation works through Blayney in Millthorpe such as a pipeline from Lake Rowlands as proposed in the Centroc study (MWH, 2009).
Browns Creek gold mine was in operation in the 1980s and 1990s with deep mining continuing through to late 1999. The mine was closed after major water ingress from an underlying aquifer occurred in December 1999. The mine pit now contains an estimate 4,700 ML of water with groundwater inflow causing a constant overflow into Cowriga Creek at a rate of between 0.4 to 1.0 ML/day. The NSW Office of Water advised the most likely allowable maximum long term pumping rate of mine water would be around 2.2 ML/day (up to 800 ML/year) (Department of commerce, 2008).
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3.8.2.2 Conceptual Transfer System
The Browns Creek mine to Orange pipeline transfer system would require: • a floating intake pump station (low lift pumps) – a floating pump station required to suit the changing level conditions in the mine pit; • a treatment system and balance tank; • a high lift pump station; and • a pipeline to connect the high lift pump station to Spring Creek Reservoir – three options were considered ranging from 26 km to 36 km in length.
The feasibility study considered three pipeline routes (Figure 47): • Option 1: along Browns Creek Road to Blayney and then long Orange Road to Millthorpe and then along the railway to Spring Creek Reservoir (31 km); • Option 2: along Browns Creek Road to Blayney and then long Orange Road to Millthorpe and then along roads to Spring Creek Reservoir (36 km); or • Option 3: shortest route from Browns Creek mine to Spring Creek Reservoir along roads (26 km).
Options 1 and 2 were sized to convey 5 ML/day to Blayney and then 10 ML/day through to Spring Creek Reservoir to allow for the possible integration with other future augmentation works. Option 3 was sized to convey 5 ML/day and would not provide the option to integrate with other future augmentation works.
3.8.2.3 Water Quantity
It was estimated that the mine pit contains 4,700 ML of water. Groundwater ingress causes the pit to maintain a full supply level with overflow discharging to Cowriga Creek at a rate of 0.4 to 1.0 ML/day.
The NSW Office of Water undertook a desktop study to assess the feasible pumping rate from which it was determined that permission could be granted for an initial extraction of up to 800 ML/year (2.2 ML/day) subject to various special conditions due to the unknown characteristics of the groundwater source. These conditions included (Department of Commerce, 2008): • monitoring surrounding groundwater levels; • reducing the pumping rate if adverse impacts occur; and • providing a minimum environmental flow release to Cowriga Creek.
It was identified that in a drought situation Orange was likely to require up to 5 ML/day which would require about 1,800 ML/year. This extraction rate would exceed the recharge rate and would draw down the stored water by around 24 m (Department of Commerce, 2008). It is unlikely this extraction rate could be sustained over the long term. Further it would prevent the overflow of water from the pit to Cowriga Creek, therefore requiring a lift pump system to maintain environmental flow.
It was identified that further work and negotiation with the NSW Office of Water would be required to establish a sustainable extraction rate.
3.8.2.4 Water Quality
Arsenic and antimony have been consistently detected in the mine water above the relevant health related drinking water guideline values. Cyanide has also previously been detected, but not in the mine water since 2002 (Department of Commerce, 2008). It was suggested that the cyanide may be present in the bottom of the water body and there was a risk that it may rise to the top during storage turnover or may become present if the storage is drawn down.
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A treatment system would be required consisting of oxidation, chemical coagulation and filtration to remove arsenic and some antimony. A reverse osmosis treatment system would be required to remove cyanide.
Source: Department of Commerce (2008)
Figure 47: Browns Creek mine to Orange pipeline route options
3.8.2.5 Secure Yield
Secure yield modelling was not undertaken for this option. However, an estimate of the potential secure yield can be derived by considering how much additional water the transfer system could provide through the critical drought period.
The NSW Office of Water informed the feasibility study and advised the most likely allowable maximum long term pumping rate of mine water would be around 2.2 ML/day (Department of commerce, 2008). This would provide an average input of around 800 ML/year. As this is a constant input, it would equate to a secure yield of around 800 ML/year.
The feasibility study identified that short term extraction of up to 5 ML/day could be possible in emergency situations by drawing on stored water in the pit as well as the groundwater recharge. This would provide around 1,800 ML/year and would again equate to a secure yield of similar magnitude as the average annual extraction. However this is unlikely to be a sustainable, particularly over the critical drought period for the Orange water supply system that lasts for around 6 years.
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Therefore it was assumed that the potential secure yield from this option would be around 1,000 ML/year.
3.8.2.6 Preliminary Capital and Operating Costs
Estimated capital costs are summarised in Table 3.53. These costs do not include land acquisition and costs associated with approvals (Department of Commerce, 2008).
Table 3.53 – Estimated capital costs for Browns Creek mine to Orange water transfer system
Option Design Capacity Capital Cost
Option 1 5 ML/day to Blayney and then 10 ML/day to Spring $32 million Creek Reservoir
Option 2 5 ML/day to Blayney and then 10 ML/day to Spring $35 million Creek Reservoir
Option 3 5 ML/day $24 million
Source: Department of Commerce (2008)
The capital costs do not include a reverse osmosis treatment system for cyanide removal. This system has estimated capital costs of $4 million (Department of Commerce, 2008). It was assumed that this unit would be required due to the risk of cyanide being present.
As discussed in Section 3.7.2, the recent study for Lake Rowlands indicates that it is unlikely to be used as the major water supply dam for regional water security strategy. Therefore it is unlikely that a pipeline connection from Lake Rowlands through to Orange (via Blayney) will be required. As such, Options 1 and 2 are not required and the shortest route (and cheapest option) would be adequate for the transfer of water from Browns Creek mine to Orange.
The long term average annual operating costs for the system were estimated based using the following assumptions: • an average daily transfer rate of 2.2 ML/day (800 ML/year); • total system power demand of 630 kW (pump stations and treatment system); • average 9.5 hours per day pumping; • average power cost of $0.22/kWhr; • water treatment costs of $0.80/kL; and • maintenance and monitoring costs of $75,000 per year.
Based on the above, the operating costs for the average annual transfer of 800 ML/year are $1,194,000/year.
3.8.2.7 Summary
Table 3.54 summarises the option of using Browns Creek mine as part of the water supply system.
Table 3.54 – Summary of Option O2: Browns Creek mine water transfer
Measure Result
Capital cost, $ $28,000,000
Operating cost, $/year $1,194,000
NPV – capital cost, ($2010) $28,000,000
NPV – operating cost, ($2010) $16,435,000
Potential increase in secure yield, ML/year 1,000
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Table 3.54 – Summary of Option O2: Browns Creek mine water transfer
Measure Result Capital costs, $/ML increase in secure yield $1,896
Operating costs, $/ML increase in secure yield $1,113
Total cost of secure yield supplied, $/ML increase in secure yield $3,009
Change in TRB if adopted $127 per assessment
Greenhouse Gas Emissions (operating power only) 2.65 tonnes CO2e/ML
Issues to consider • Water quality • Groundwater impacts • Sustainability of groundwater extraction
Likely timeframe to complete 3 to 5 years
3.8.3 WATER CARTING
Water carting options were investigated in 2009 as the city’s water supplies fell to very low levels. This investigation was undertaken by NSW Water Solutions and assessed the broad feasibility of a range of options for water cartage to Orange to meet immediate and essential demand (NSW Water Solutions, 2009).
Supply options investigated included Molong Dam and Burrendong Dam, Browns Creek mine and the town water supplies at Blayney and Bathurst. Road and rail transport options were considered for the delivery of 4.8 ML/day. Road transport options for the delivery of 4.8 ML/day would require 178 tanker loads each day equating to a tanker load every eight minutes. This would require up to 25 tankers each making at least nine trips a day for a 24 hour, seven day a week carting operation. Rail transport options for the delivery of 4.8 ML/day would require about seven train loads each day equating to a train every 110 minutes.
Table 3.55 summarises the supply and delivery options investigated and the potential volume supplied from each source.
Table 3.56 presents a summary of the capital and operating costs for each option along with the cost per ML for a three month supply. These costs include the purchase of the water from the relevant authority.
The study concluded that water cartage to Orange to meet the minimum demand would be an expensive exercise (refer to Table 3.56) and that “prior to considering cartage, Orange City Council should exhaust all other reasonable options for ensuring the continuity and efficient long term management of its water supply” (NSW Water Solutions, 2009: ix).
The final recommendation was “that any further contingency planning proceed on the basis of road/rail cartage from Blayney based on water from Lake Rowlands and from Bathurst based on water from Ben Chifley. At least 6-month lead-time should be allowed for detailed planning for water cartage by road or rail” (NSW Water Solutions, 2009: ix).
It was highlighted that if water cartage of 4.8 ML/day was required for six months or longer, other permanent options such as pipelines from Browns Creek mine or Burrendong Dam would warrant consideration.
The report identifies the measures required to implement a water cartage operation. The cost of the water is extremely high and as such greater emphasis should be placed on other permanent water security measures.
As such, water cartage is not seen as a viable long term solution to improve Orange’s water security and is not considered further in the IWCM Evaluation Study.
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Table 3.55 – Water cartage options
Water Source Supply Transport Delivered to Road Rail
Molong Dam raw water – 2 ML/day na Road: sourced from a filling point at • Icely Road WTP the intersection of Bruce Road • Stormwater harvesting holding pond and the Mitchell Highway
Molong Dam and Borenore 2 ML/day na Road: Creek Dam raw water – • Icely Road WTP sourced from a filling point at • Stormwater harvesting holding pond Fairbridge Park
Blayney town water (Lake 3 ML/day Road: Rowlands filtered water) – • Icely Road WTP road filling sourced from a • Elsham Avenue – Leewood Park Industrial Estate filling point at the intersection • Bloomfield Park – Gosling Creek Reservoir of Orange Road and Palmer • Gosling Creek at Mitchell Highway Street. Rail filling near Plumb Rail: Street • McNeilly Avenue, north of Ash Street • Dane Lane, south of Ash Street
Browns Creek mine raw water 4.8 ML/day Road: - sourced from a filling point at • Icely Road WTP the intersection of Orange • Elsham Avenue – Leewood Park Industrial Estate Road and Palmer Street • Bloomfield Park – Gosling Creek Reservoir • Gosling Creek at Mitchell Highway Rail: • McNeilly Avenue, north of Ash Street • Dane Lane, south of Ash Street
Bathurst town water (Ben 4.8 ML/day Road: Chifley Dam filtered water) – • Icely Road WTP road filling sourced from a • Elsham Avenue – Leewood Park Industrial Estate filling point at the intersection • Bloomfield Park – Gosling Creek Reservoir of Bradwadine Road and the • Gosling Creek at Mitchell Highway Mitchell Highway. Rail filling at Rail: Bathurst Railway Station • McNeilly Avenue, north of Ash Street • Dane Lane, south of Ash Street
Bathurst town water (Ben 4.8 ML/day na Road: Chifley Dam filtered water) – • Icely Road WTP road filling sourced from a • Elsham Avenue – Leewood Park Industrial Estate filling point at Hereford Street. • Bloomfield Park – Gosling Creek Reservoir • Gosling Creek at Mitchell Highway
Burrendong Dam raw water – 4.8 ML/day na Road: sourced from a filling station at • Icely Road WTP Mumbil • Stormwater harvesting holding pond
Source: NSW Water Solutions (2009)
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Table 3.56 – Water cartage summary of capital and operating costs
Water Source Supply Transport Capital Daily Cost for 3 Operating Month Supply $M $ $/ML
Molong Dam raw water 2 ML/day Road $3.19 $35,166 $35,667
Molong Dam and Borenore 2 ML/day Road $3.04 $40,326 $37,500 Creek Dam raw water
Blayney town water (Lake 3 ML/day Road $4.35 $59,608 $36,444 Rowlands filtered water)
Browns Creek mine raw water 4.8 ML/day Road $14.51 $73,560 $49,236
Bathurst town water (Ben 4.8 ML/day Road $7.35 $113,217 $41,111 Chifley Dam filtered water)
Bathurst town water (Ben 4.8 ML/day Road $4.13 $123,142 $35,764 Chifley Dam filtered water)
Burrendong Dam raw water 4.8 ML/day Road $14.5 $114,714 $58,009
Blayney town water (Lake 3 ML/day Rail $6.87 $153,983 $77,889 Rowlands filtered water)
Browns Creek mine raw water 4.8 ML/day Rail $19.25 $272,282 $102,546
Bathurst town water (Ben 4.8 ML/day Rail $8.51 $416,650 $108,426 Chifley Dam filtered water)
Source: NSW Water Solutions (2009)
3.8.4 LONG LIST RECOMMENDATIONS
The following long list of potential other options can be derived from the above assessment: • O1: Lucknow Mine – Reform shaft; • O2: Browns Creek Mine; and • O3: Water carting.
Further consideration and short listing of options is presented in Section 4.
3.9 DEMAND MANAGEMENT
3.9.1 INTRODUCTION
Assessment of potential demand management options was based on two approaches: 1. Adjusting the water restriction rules used for secure yield modelling relating to the frequency and duration of restriction periods. This provided a theoretical increase in secure yield; and 2. Using the DEUS Demand Management Decision Support System (DSS) version S1.1 (DEUS, 2006) to estimate the potential water saving provided by conservation water pricing. This is where the pricing of water is based on the quantity available for consumption. Lower quantities will demand higher prices to discourage excessive consumption.
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3.9.2 RESTRICTION FREQUENCY AND DURATION Secure yield is the annual demand that can be supplied from a water supply system while satisfying the following conditions:
a) Duration of restrictions does not exceed 5% of the time;
b) Frequency of restrictions does not exceed 1 year in 10 on average; and
c) Severity of restrictions does not exceed 10%. Systems must be able to meet 90% of the unrestricted water demand (i.e. 10% average reduction in consumption due to water restrictions) through a repetition of the worst recorded drought, commencing with the storage drawn down to the level at which restrictions need to be imposed to satisfy a) and b) above. This is referred to in the IWCM Evaluation Study as the 5/10/10 rule.
If the duration of restriction periods is increased and they occur more often, the secure yield for a system increases. This is because the community is accepting restrictions more often and for longer periods, which saves stored water.
Three variations to the 5/10/10 rule were examined: • Longer and more frequent restriction periods i.e. 10/5/10 rule; • More frequent restriction periods i.e. 5/5/10 rule; and • Much longer and more frequent restriction periods i.e. 20/2/10 rule.
It should be noted that the adoption of these secure yield rules does not meet best practice or Orange City Council’s agreed level of service. They have been analysed to provide a sensitivity analysis relating to the secure yield modelling assumptions.
Finally, it is noted that when this assessment was undertaken, the secure yield modelling was adopting the 5/10/20 rule (this has subsequently been changed to the 5/10/10 rule in accordance with best practice). It is expected that the incremental change provided by each rule change would be the same regardless of the severity of restriction rule adopted. Therefore only the incremental secure yield is reported, rather than the total secure yield value.
The secure yield modelling was based on the natural water supply system (Spring Creek Reservoir and Suma Park Reservoir and their catchments).
3.9.2.1 Longer and More Frequent Restriction Periods
The potential increase in secure yield gained by accepting longer and more frequent restrictions was examined assuming a 10/5/10 rule; that is: a) Duration of restrictions does not exceed 10% of the time; b) Frequency of restrictions does not exceed 1 year in 5 on average; and c) Severity of restrictions does not exceed 10% (as above).
The increase in secure yield by adopting longer and more frequent restrictions is 300 ML/year.
3.9.2.2 More Frequent Restriction Periods
The potential increase in secure yield gained by accepting longer and more frequent restrictions was examined assuming a 5/5/10 rule; that is: a) Duration of restrictions does not exceed 5% of the time; b) Frequency of restrictions does not exceed 1 year in 5 on average; and c) Severity of restrictions does not exceed 10% (as above).
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There was no change in the secure yield value by adopting this rule (noting that the secure yield modelling is based on increments of 50 ML/year).
3.9.2.3 Much Longer and More Frequent Restriction Periods
The potential increase in secure yield gained by accepting longer and more frequent restrictions was examined assuming a 20/2/10 rule; that is:
a) Duration of restrictions does not exceed 20% of the time;
b) Frequency of restrictions does not exceed 1 year in 2 on average; and
c) Severity of restrictions does not exceed 10% (as above).
The increase in secure yield by adopting longer and more frequent restrictions is 800 ML/year.
3.9.2.4 Discussion
The above analysis demonstrates how assumptions relating to the duration and frequency of restriction periods can alter the secure yield. It is noted that these changes do not meet State Government best practice requirements and therefore should not be considered as part of the water security solution for Orange. The analysis does however provide an indication of the sensitivity of the secure yield calculation to restriction assumptions.
Issues associated with the changes in secure yield model assumptions are: • it does not meet State Government best practice and Orange City Council’s agreed level of service; and • it would require community acceptance which would raise issues relating to equity between communities across the region.
3.9.3 CONSERVATION WATER PRICING
Technical Note 3 presents an assessment of current and future water demand and the impact of the various measures Orange City Council uses to manage demand. The BAU scenario includes the following demand management measures: • user pay pricing structure; • BASIX compliance; • community education/public awareness campaigns; • showerhead exchange program; • non-residential water audits; • water restriction implementation; • system loss management; • permanent water conservation measures; and • an alternative water supply for the dual reticulation area.
The forecast water demand at 10 year intervals derived for the BAU scenario are summarised in Table 3.57.
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Table 3.57 – Orange forecast water demand – BAU
Demand Growth 2010 2020 2030 2040 2050 2060
Per Capita Water Demand (L/p/d) na 404 370 362 357 351 346
Average Annual (ML/a) Medium: 0.8%pa 5,403 5,349 5,681 6,058 6,478 6,948
High: 1.1%pa 5,403 5,515 6,045 6,655 7,347 8,135
Peak Day Water Demand (ML/d) Medium: 0.8%pa 32.5 32.7 35.5 38.0 40.6 43.5
High: 1.1%pa 32.5 33.9 37.9 42.0 46.4 51.4
The total per capita water demand includes non-residential use (i.e. commercial, industrial, public and open space water)
High level demand management would include the introduction of conservation pricing for residential users (on top of the BAU scenario). The assumptions used to assess the market penetration and demand reduction potential of this option are provided in Technical Note 3. Results are reproduced in Table 3.58. It shows that the introduction of conservation water pricing could reduce potable water demand in 2040 by 220 to 245 ML/annum from the BAU scenario.
Table 3.58 – Orange forecast water demand – high level demand management
Demand Growth 2010 2020 2030 2040 2050 2060
Per Capita Water Demand (L/p/d) na 404 356 349 344 339 334
Average Annual (ML/a) Medium: 0.8%pa 5,407 5,157 5,474 5,838 6,244 6,698
High: 1.1%pa 5,407 5,316 5,824 6,410 7,078 7,838
Peak Day Water Demand (ML/d) Medium: 0.8%pa 32.5 30.5 33.1 35.4 37.9 40.6
High: 1.1%pa 32.5 31.6 35.4 39.2 43.3 47.9
The total per capita water demand includes non-residential use (i.e. commercial, industrial, public and open space water)
A review of conservation water pricing (scarcity pricing) undertaken as part of the Centroc study concluded there is inadequate support to recommend an independent scarcity pricing arrangement for the Council members of Centroc (MWH, 2009).
3.9.4 LONG LIST RECOMMENDATIONS
The following long list of demand management options can be derived from the above assessment: • D1: Longer and more frequent restriction periods i.e. 10/5/10 rule; • D2: More frequent restriction periods i.e. 5/5/10 rule; • D3: Much longer and more frequent restriction periods i.e. 20/2/10 rule; and • D4: conservation water pricing.
Further consideration and short listing of options is presented in Section 4.
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Assessment of Options
4.1 INTRODUCTION
Orange City Council adopted a comprehensive Strategic Water Supply Strategy at its meeting of 19 November 2009. The strategic objective of the strategy is:
To establish a broad based water supply strategy for the next 50 years and beyond which focuses on ongoing water conservation, quality and demand management and the provision of key water supply infrastructure at least 10 years in advance of projected demand.
The ultimate aim of the strategy is to see fewer restrictions, improved security, and capacity for ongoing growth.
The strategy outlined a number of actions aimed at meeting its strategic objective. These actions addressed the following elements: • Water conservation and quality and demand management; • Provision of infrastructure – priority local options, priority regional options and alternative options; • Management, promotion and lobbying; and • Funding.
A key element of the strategy is that it is based on delivering water supply infrastructure up to 10 years prior to the projected demand. This responsible strategic approach to water supply planning avoids short term and often costly decisions made under emergency conditions.
This section examines water security for Orange in line with the adopted strategy. Specifically it: • examines if the water infrastructure works proposed as Council’s BAU scenario will meet the stated water security objective; and • identifies the preferred options to meet any future shortfall.
This review applies to the Orange water supply only. The villages of Spring Hill and Lucknow are supplied from groundwater sources and modelling of this system (as presented in Technical Note 3) indicates adequate supplies for the next 50 years.
4.2 WATER SECURITY
4.2.1 COMPARING SECURE YIELD WITH DEMAND
Section 3 presents details of the various water sources considered by Orange City Council to provide long term water security including: surface water, stormwater, rainwater, groundwater, treated effluent, regional supplies, other emergency solutions and demand management.
Some components have been successfully implemented such that the existing water supply system includes: • Gosling Creek, Spring Creek and Suma Park Reservoirs and their catchments; • input from the approved stormwater harvesting schemes in Blackmans Swamp Creek (Stage 1a) and Ploughmans Creek; and • a system of four bores.
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The secure yield of this system based on the 5/10/10 rule is 4,750 ML/year as summarised in Table 4.1.
Table 4.1 – Existing water system secure yield
Secure yield from Total secure yield Water source source ML/year ML/year
Gosling Creek, Spring Creek and Suma Park Reservoirs 3,400 3,400
Approved harvesting schemes: 900 4,300 Blackmans Swamp Creek system operating on 50% trigger; Ploughmans Creek system operating on 100% trigger.
Licensed bore extraction: 450 4,750 Four bores supplying 462 ML/year
Technical Note 3 presents an assessment of the current and future water demand for Orange. This assessment shows that the current unrestricted annual water demand in 2010 is 5,400 ML/year. Therefore, the existing secure yield of 4,750 ML/year is 650 ML/year short of the current unrestricted demand. As the community grows, so too will the gap between demand and supply. This is illustrated in Figure 48.
This mismatch between demand and supply will not be evident in average or wet conditions; only in prolonged drought. Best practice water supply design requires the system to be designed and built now to get Orange through such a drought.
Orange City Council has adopted a 50 year planning horizon to ensure long-term water supply security the city. In addition, the strategy adopts the approach of having a water supply scheme capable of meeting projected water demands at least 10 years in advance. This is a prudent measure to provide sufficient lead time should the gap between secure yield and demand be smaller than forecast and further system augmentation is required sooner than expected.
This is illustrated in Figure 48 where the solid dark blue line represents the medium growth in water demand and the dotted dark blue line a high water demand growth. The red dotted line represents the secure yield which needs to be provided in each year if the supply system to meet high demand projections is available 10 years in advance and the solid red line if medium demand is to be met 10 years in advance.
The gap between the red lines and the horizontal blue band that represents the total existing secure yield shows the increment in secure yield which is required to be in place in any year to meet the target of being able to match demand 10 years in advance. Using Council’s 50 year adopted planning horizon, Figure 48 shows that in increment of 2,700 ML is needed to meet projected medium demand growth or 4,300 ML/year to meet the high demand growth.
To provide water security over the 30 year IWCM planning period the secure yield targets are 6,480 ML/year and 7,350 ML/year for the medium and high growth respectively (these values represent the forecast demand in 2050). Over this period an increment of 1,700 ML/year is needed to meet projected medium demand growth or 2,600 ML/year to meet the high demand growth.
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Natural Catchment Secure Yield Bores @ 462 ML/year Secure Yield Approved Stormwater Harvesting Secure Yield Water Demand Medium Growth (BAU) Water Demand High Growth (BAU) High growth secure yield target Medium growth secure yield target 10000
9000
Shortfall high growth 8000 = 4,300 ML
7000 Shortfall medium growth = 2,700 ML 6000 ML/year
5000
4000
3000
2000
1000
0 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060 Year
Figure 48: Water security for existing water supply infrastructure – no climate change
4.2.2 SENSITIVITY OF PROJECTIONS 4.2.2.1 Climate Change
The NSW Government has undertaken a pilot study to see how changes in climate might affect water supply secure yield and provided a guideline on how changes in secure yield by 2030 can be assessed (Samra and Cloke, 2010). The intention of the guideline is to strike a balance between prudent provision of water supply infrastructure which can accommodate a potential reduction in yield over the next 20 years without over investing in assets which may not be required.
Orange City Council was one of the utilities used in the pilot study to define the methodology for the assessment of climate changed secure yield (Samra and Cloke, 2010). Results from this pilot study indicate that a climate change reduction factor of 26% applies to the existing catchment and storage system (i.e. the existing catchment and storages without additional sources).
Climate changed secure yield was assessed using the procedures described by Samra and Cloke (2010) for the BAU water supply components (excluding Blackmans Swamp Creek Stage 2 harvesting). This assessment included the addition of input from the stormwater harvesting schemes, bores and the Macquarie River to Orange pipeline operating on the proposed 12/34 operating rule.
A summary of this assessment is provided in Appendix C and shows a reduction factor of 6% to 8% can be applied to the best estimate of secure yield. This indicates that by diversifying and augmenting the water sources, the water supply system has become more resilient to the potential impacts of climate change (i.e. the climate change reduction factor has reduced from 26% to 6%).
The current secure yield is made up of three water sources: existing catchments; approved harvesting; and bores. Therefore the climate change reduction factor for the existing system would lie somewhere between 6% and 26%. For the purposes of this assessment, a climate change reduction factor of 10% was adopted for the existing system. The method assumes that secure yield is reduced by 10% by 2030 and there is a linear reduction between now and then.
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Such changes in climate might not only result in a reduction in yield but a hotter or drier climate or more variable rainfall may also result in an increase in demand. The Centroc water security study provided an assessment of the possible impact of climate change on water demand. For Orange this assessment indicated the potable water demand could increase by around 7% or about 400 ML per year in 2050 (MWH, 2009).
As shown in Figure 49, the gap between current supply and future demand will widen in this climate change scenario with the shortfall for the 50 year planning horizon being between about 3,900 to 5,500 ML/year.
To provide water security over the 30 year IWCM planning period the secure yield targets are 6,950 ML/year and 7,880 ML/year for the medium and high growth respectively (these values represent the forecast demand in 2050). Over this period an increment of 2,670 ML/year is needed to meet projected medium demand growth or 3,600 ML/year to meet the high demand growth.
Natural Catchment Secure Yield Bores @ 462 ML/year Secure Yield Approved Stormwater Harvesting Secure Yield Water Demand Medium Growth (BAU) Water Demand High Growth (BAU) High growth secure yield target Medium growth secure yield target 10000
Shortfall high 9000 growth= 5,500 ML
8000 Shortfall medium growth = 3,900 ML
7000
6000 ML/year
5000
4000
3000
2000
1000
0 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060 Year
Figure 49: Water security for existing water supply infrastructure – with climate change
4.2.2.2 Additional Demand Management
As discussed in Section 3.9.3 and detailed in Technical Note 3 there are limited options for further demand management in addition to those which are already adopted as part of the BAU scenario. With the introduction of conservation pricing, it might be possible to reduce medium growth water demand to 5,474 ML/year by 2030 and 5,824 ML/year in the same year should growth rates be high, a reduction of between 210 and 220 ML/year.
This does not significantly change the shortfall. It is evident that additional water sources are required to provide long term water security.
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4.3 BUSINESS AS USUAL WATER SECURITY
The 2009 Strategic Water Supply Strategy forms the basis of Orange City Council’s business as usual (BAU) scenario. The water demand elements of the BAU scenario have been incorporated into the water demand forecasting that is presented in Technical Note 3 and shown on Figures 47 and 48.
The local and regional water supply infrastructure components identified in the BAU scenario and their current status are summarised in Table 4.2.
Table 4.2 – Water supply management strategy infrastructure options
Component Comment Status
Priority local options
Fast tracking the development and construction Construction of the Ploughmans Creek Complete of the Ploughmans Creek Stormwater stormwater harvesting scheme was completed Harvesting scheme as an emergency water in mid-2011. A licence was granted under supply project, subject to compliance with Section 10 of the Water Act 1912 (Licence appropriate environmental and regulatory 80SL96331) for the permanent operation of the requirements, for completion in the first half of scheme in August 2011. The scheme has not 2010 been operated to date due to adequate water storages levels.
Commissioning of bores at the Orange Licensing grated in March 2012 for the Complete Showground, Clifton Grove and Endeavour extraction of a combined 462 ML/year from the Field (following agreement with existing users) Showground, OCC depot and Clifton Grove as an emergency water supply project, subject bores. The endeavour Field bore will no longer to compliance with appropriate environmental be considered as part of the water supply and regulatory requirements, for connection to system. the water supply system in the first half of 2010.
Completion of safety upgrading works at Suma Investigation and design work in progress. This In progress Park Dam including the adoption of operational work includes examining the option of raising rules which do not require the dam to be raised the dam. Environmental flow studies are also above its existing full supply level but enable being undertaken. the existing storage to be utilised more efficiently through the development of additional points of supply, such as stormwater harvesting.
Priority regional options
Undertake a detailed feasibility analysis Macquarie Pipeline: In progress immediately into the establishment of an • Feasibility study completed May 2010. emergency water supply pipeline connection • Concept study completed January 2011. from the Macquarie River downstream of • Statutory approval process commenced Bathurst to Orange, and as a secondary option, March 2011. from Lake Rowlands to Orange (subject to the availability of suitable water volumes and Lake Rowlands Pipeline: agreement on business arrangements with • Lake Rowlands yield study completed Central Tablelands Water(CTW)), to confirm November 2011. concepts and, if suitable, undertake the • Secure yield results indicate that there is necessary statutory assessments to prepare for unlikely to be significant “spare” secure construction in order to optimise delivery of yield to supply Orange, particularly when project/s, ideally within 2 years. climate change is considered.
Pursue State and Federal Government funding State and Federal Government funding totalling Complete for regional pipelines in the priority order of both $38.2 million approved in March 2011 for the the Macquarie River and Lake Rowlands Macquarie pipeline project. pipeline (subject to agreement with CTW) firstly, failing which, the Macquarie River pipeline only.
Failing State and Federal Government funding State and Federal Government funding totalling Complete of the Macquarie/Rowlands pipeline options, $38.2 million approved in March 2011 for the the Macquarie River pipeline be targeted to be Macquarie pipeline project. secured in the medium term and the CTW connection in the medium/long-term (again subject to agreement with CTW on suitable volumes and business arrangements).
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Table 4.2 – Water supply management strategy infrastructure options
Component Comment Status Support the outcomes of the Centroc Water Council has continued to work with Centroc to In progress Security Study including promotion of the progress this strategy. expansion of Lake Rowlands and associated pipelines in principle for the pursuit of State and Federal funding and for the negotiation of suitable access, volume, water charges and business arrangements and for full feasibility analysis
Alternative options (to be pursued following the above options or in lieu of the priority options if they cannot be achieved in the short term
Connection of Lake Canobolas into the city’s • Investigations completed in March 2011. Investigation complete water supply network, subject to compliance • Recommended as emergency connection with appropriate environmental and regulatory to be used when main storage levels fall to requirements including the establishment of less than 25%. appropriate operating rules to regulate operation of this system.
Direct connection from Gosling Creek Dam into • Maintaining storage levels and using stored Investigation complete the city’s water reticulation network, including water when the main storage levels fall to provision of appropriate water treatment less than 25% by transfer through to Spring infrastructure, subject to compliance with Creek Reservoir now considered to be appropriate environmental and regulatory more appropriate than direct connection. requirements including the establishment of appropriate operating rules to regulate operation of this system.
Development of the second stage of the • Council is participating in a process to Waiting outcome of Blackmans Swamp Creek Stormwater resolve objections to the licensing of Stage Blackmans Swamp Harvesting Scheme generally as outlined in the 1. Until this is resolved, Stage 2 will not be Creek Stormwater original approval for this project. pursued. Harvesting Scheme • Further, Council needs to comply with a Stage 1 licence water quality approval process before application. expansion of the stormwater harvesting schemes will be considered.
Investigation into the feasibility of developing a • Managed Aquifer Recharge (MAR) In progress Managed Aquifer Recharge system in business case prepared June 2011. conjunction with the Federal Government. • Recommended MAR trial to establish operational information relating to aquifer storage and reuse.
Source: Orange City Council (2009)
In summary the BAU water supply components include the existing system of catchments and dams plus: • bores adding 462 ML/year; • Ploughmans Creek stormwater harvesting scheme operating on a 100% trigger; • full licensing of Blackmans Swamp Creek Stage 1 (i.e. operating on a 100% trigger); • raising Suma Park Dam by 1.0 m in conjunction with dam safety upgrade works; • the Macquarie River to Orange pipeline; and • Blackmans Swamp Creek Stage 2 stormwater harvesting.
The water security provided by the BAU scenario is demonstrated in Figure 50. This shows that the proposed BAU water supply infrastructure components provide water security for 50 years.
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Water Demand (BAU) Water Demand High Growth (BAU) Water Demand Medium Growth (BAU) Secure Yield Historical Water Demand Estimated Water Demand Without Restrictions 10000
BSC Stage 2 9000
Macquarie River 12/34 8000
7000
6000
ML/year Blackmans Swamp Ck harvesting fully licenced + raise Suma Park Dam 5000
4000 Approved stormwater harvesting + bores @ 462 ML/yr 3000 Natural Catchment
2000 Existing water supply components
1000 Water supply components (subject to approval)
0 1995 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060 Year
Figure 50: Water security with BAU water supply infrastructure – no climate change
As detailed in Section 4.2.2.1, climate changed secure yield was assessed using the procedures described by Samra and Cloke (2010) for the BAU water supply components (excluding Blackmans Swamp Creek Stage 2 harvesting). This assessment showed a climate change reduction factor of 6% to 8% can be applied to the best estimate of secure yield (refer to Appendix C).
The water security picture adopting an 8% reduction in secure yield through to 2030 due to climate change and a 7% increase in demand is illustrated on Figure 51. If these changes eventuate, the construction/commissioning of Blackmans Swamp Creek Stage 2 stormwater harvesting would need to be brought forward by about 10 years. Further water supply options would be required beyond about 2043 to remain 10 years in front of the high demand. Medium growth water demand can be met for the next 50 years.
Figure 51 demonstrates that even under climate change assumptions, the BAU water supply components provide water security for at least the next 30 years. It is therefore concluded that the BAU actions will address the IWCM target of providing water security in accordance with the 5/10/10 secure yield rule.
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Water Demand (BAU) Water Demand High Growth (BAU) Water Demand Medium Growth (BAU) Secure Yield Historical Water Demand Estimated Water Demand Without Restrictions 10000
9000 BSC Stage 2 Macquarie River 12/34 8000
7000
6000
ML/year Blackmans Swamp Ck harvesting fully licenced + raise Suma Park Dam 5000
4000 Approved stormwater harvesting + bores @ 462 ML/yr 3000 Natural Catchment
2000 Existing water supply components
1000 Water supply components (subject to approval)
0 1995 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060 Year
Figure 51: Water security with BAU water supply infrastructure – with climate change
4.4 FUTURE WATER SUPPLY OPTIONS
4.4.1 UPDATE SINCE PRG MEETING 3
The preceding section demonstrates that Council’s current BAU water supply actions will provide water security for at least the next 30 years, which satisfies the IWCM planning period.
It is noted that this is not the position that was presented to PRG Meeting 3 in December 2011. At that time, the secure yield determined for the Macquarie River to Orange pipeline project was 1,600 ML/year and this coupled with other BAU water supply components did not provide security beyond about 2030.
Therefore the PRG was advised that additional water security options (i.e. in addition to the BAU water supply components) would be required to meet forecast water demand to 2040 and comply with the 5/10/10 design standard for imposing water restrictions.
The PRG reviewed the long list table and worked through a quadruple bottom line (QBL) process to identify the preferred water supply options from the short listed options.
While this process was valuable in identifying some underlying preferences and did identify a preferred order for the short listed options, it is no longer required.
Of course, all future BAU water supply components are subject to gaining the required environmental planning approvals and licences. During this process the scope of the component may change, or indeed, it may not gain approval. In this case other options would need to be investigated. It is considered that the short listed options and the QBL process has identified the preferred options that should be considered next if elements of the BAU do not eventuate.
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The short listing and QBL process is described in the following sections to provide a record of the process.
4.4.2 LONG LIST OF OPTIONS
Table 4.3 provides the long list of options derived from the review presented in Section 3. The long list was screened at a high level by the IWCM steering committee and short-listed based on consideration of the secure yield, the cost effectiveness of the option and issues associated with gaining approval. Items that were already part of Council’s BAU scenario were not short listed as options as these options have already been committed to by resolution of Council.
Considerations for not short-listing are summarised in Table 4.3. The long list and short list was reviewed at PRG Meeting 3.
Table 4.3 – Long list options
Potential $ per ML Impact on Increase Short ID Option Secure in Considerations for not Short-listing listed? Yield Secure ML/year Yield SW1 Raising Suma Park Dam 100 - 200 $1,202 to No Included in BAU scenario $2,404
SW2 Lake Canobolas 100 $2,474 No • Marginal secure yield increase (~100 ML/year). • Impact on recreational lake. • Licencing and approval issues. • Considered not to be a permanent solution, but available as an emergency supply with connection via Cargo Road Reservoir.
SW3 Macquarie River to 2,800 $1,190 No Included in BAU scenario Orange pipeline ($396 with grants)
SW4 Burrendong pipeline 2,800 $2,017 Yes ($1,681 with grant)
SW5 Mulyan Creek Dam 430 $5,588 Yes
SW6 Cadia Valley Operations unknown n/a No • Acknowledged as a long term option. water infrastructure • Other options available at the end of the mine life (i.e. treated effluent).
SW7 Manage evaporation ~ 800 $14,494 No • Very high cost per ML of secure yield from surface water increase storage • Better options available. • Risk of floating structure to dam integrity.
SW8 De-silting Spring Creek < 100 n/a No • Estimated only to increase the available Dam storage by 148 ML. • No significant impact on the secure yield. • High costs and challenging logistics.
SH0 Blackmans Swamp 200 $428 No Included in BAU scenario Creek SHS Stage 1b
SH1 Blackmans Swamp 900 $812 No Included in BAU scenario Creek SHS Stage 2
SH2 Blackmans Swamp 1,000 $1,061 Yes Creek SHS Stage 3
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Table 4.3 – Long list options
Potential $ per ML Impact on Increase Short ID Option Secure in Considerations for not Short-listing listed? Yield Secure ML/year Yield
SH3 Maximum Blackmans 700 $514 No • Extremely unlikely to gain Swamp Creek SHS approval/licensing due to large extraction volume in the Summer Hill Creek water source. • Issues related to the difficult in getting approval for Stage 3. • Non-diversification of water sources.
SH4 Upstream stormwater 200 - 400 $1,419 to No • Modelling indicated these systems could harvesting $2,752 realise a secure yield increase in the (Blackmans/Rifle Range order of 200 to 400 ML/year once the Creeks south of railway) catchment areas are fully developed. • The runoff from these catchments contributes to the downstream harvesting system. • Better considered as a longer term option that could tap into the additional runoff created when these areas are developed. • Systems could be combined as stormwater management devices at that time to help manage stormwater. • Disadvantage is that upstream harvesting would require de-centralised water treatment systems to deliver treated harvested stormwater to Spring Creek dam.
SH5 Beer Road stormwater 100 $2,805 No • Modelling indicated this system could harvesting realise a secure yield increase in the order of 100 ML/year once the catchment areas are fully developed. • Better considered as a longer term option that could tap into the additional runoff created when these areas are developed. • Systems could be combined as stormwater management devices at that time to help manage stormwater. • Small system that does not meet current secure yield deficit.
RW1 Rainwater tanks 300 $11,044 Yes
GW1 Increasing bore licence 350 $876 No Included in BAU scenario by 387 ML/year to a total of 462 ML/year
GW2 New bores in Orange Unknown n/a No • Orange basalt is a good aquifer, but basalt zone difficult to predict yields and hard to control impacts. • Potential impact on existing users. • Groundwater option best used in conjunction with surface water resources through a Managed Aquifer Recharge scheme (see GW3).
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Table 4.3 – Long list options
Potential $ per ML Impact on Increase Short ID Option Secure in Considerations for not Short-listing listed? Yield Secure ML/year Yield
GW3 Managed Aquifer Depends on n/a No • Trial MAR investigation included in the Recharge inputs BAU scenario. • Information gained from the trial will be used to further assess MAR options. • MAR on its own does not increase secure yield – additional inputs are required from other sources i.e. stormwater harvesting, Macquarie River pipeline.
GW4 New bores in north Unknown n/a No • Low yielding groundwater system. Orange • Potential impact on existing users. • Groundwater option best used in conjunction with surface water resources through a Managed Aquifer Recharge scheme (see GW3).
E1 IPR 1: Non-membrane 3,400 $1,832 No • NSW Offie of Water very unlikely to system treating 10 support an Indirect Potable Reuse (IPR) ML/day scheme without membrane technology as a barrier for public health reasons. Note: IPR = Indirect • Sufficient effluent not available until at Potable Reuse least 2030 (current estimated mine life).
E2 IPR 2: Membrane 3,300 $2,168 Yes • Option for beyond 2030 as insufficient system treating effluent available due to existing effluent 10 ML/day supply agreement.
E3 Using treated effluent to n/a n/a No • Insufficient information available at this supplement flow and stage on the impact of using effluent to increase harvesting on supplement creek flows. Blackmans Swamp • Draft Water Sharing Plan prohibits Creek construction of Stage 3 weir. • Environmental flow requirements in Blackmans Swamp Creek and Summer Hill Creek are subject to investigation. • Potential impact on effluent availability for the CVO agreement. • Incurs load based licence fees.
E4 Third pipe system to < 100 n/a No • Very high reticulation costs into already parks and gardens developed areas. • Public health risk requires high level of treatment. • Not large volumes of potable water saved.
E5 Wet weather flow < 100 $2,886 No • Only captures around 80 to 150 ML/year capture at STP of effluent. • Low secure yield potential. • Moderate cost per ML. • Need to treat effluent before reuse.
E6 Decentralised STPs with Unknown n/a No • The existing STP has sufficient capacity local reuse to meet forecast loads through to 2040. • Would represent an underutilisation of assets. • Water quality risk issues.
E7 Greywater reuse ~ 300 n/a No • Would require decentralised/individual treatment systems. • The existing STP has sufficient capacity to meet forecast loads through to 2040.
R1 Lake Rowlands 970 $5,597 Yes
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Table 4.3 – Long list options
Potential $ per ML Impact on Increase Short ID Option Secure in Considerations for not Short-listing listed? Yield Secure ML/year Yield
R2 Molong Creek Dam Nil n/a No • Secure yield of Molong Dam approximately equal to the existing baseline demand. Therefore no spare capacity to provide a supply to Orange.
O1 Lucknow Mine < 100 n/a No • Low yield – estimated at 2 ML/week (~100 ML/year). • Risk of shaft collapse due to de- watering. • Possible impact on surrounding groundwater tables. • Would require comprehensive hydrogeological and geotechnical investigation prior to an abstraction licence being granted.
O2 Browns Creek Mine 1,000 $3,009 No • Estimated to provide up to 2 ML/day, which would equate to an approximated secure yield increase of 1,000 ML/year. • Expensive option per ML due to treatment and transfer costs > $3,000/ML increase in secure yield. • Possible impacts on surrounding groundwater tables and existing licence holders.
O3 Water carting n/a – short n/a No • Very expensive option with cost ranging term option between $35,000 to $108,000 per ML only for a 3 month supply. • Considered to be a “last resort” option.
D1 Longer and more 300 n/a Yes • This option was short listed but it is frequent restriction noted that it does not meet NSW Office periods i.e. 10/5/10 rule of Water best practice guideline of adopting the 5/10/10 rule for water security planning. • Does not meet Council’s LOS.
D2 More frequent restriction 100 n/a No • Does not meet NSW Office of Water periods i.e. 5/5/10 rule best practice guideline of adopting the 5/10/10 rule for water security planning. • Does not meet Council’s LOS.
D3 Much longer and more 800 n/a No • Does not meet NSW Office of Water frequent restriction best practice guideline of adopting the periods i.e. 20/2/10 rule 5/10/10 rule for water security planning. • Does not meet Council’s LOS.
D4 Conservation water 200 - 250 n/a No • Not supported in the Centroc Water pricing Security Study • Better options available • Needs link to regional demand management plan (Centroc)
4.4.3 SHORT LIST OPTIONS
Table 4.4 provides the short-list of potentially feasible options for water security improvements following screening from the long list. This includes results from a desk top feasibility assessment of each option (Section 3). It should be noted that most cost estimates provided in this document are strategic planning level assessments that would require further refinement during the concept and detailed design phases. As such, they should only be relied upon for the purposes of making comparisons between options.
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Table 4.4 – Short-listed water security options
Increase Capital Annual $/ML Change in TRB in Secure Costs Operating (1) increase if adopted ID Option Yield Costs in secure
yield $/assessment ML/year $’000 $‘000/year
D1 More frequent and longer 300 nil nil n/a nil restriction periods i.e. 10/5/10 rule
SW4 Burrendong pipeline (2) (3) 2,800 $84,486 $734 $1,681 +$213
SW5 Mulyan Creek Dam 430 $43,163 $151 $5,588 +$109
SH2 Blackmans Swamp Creek Stage 3 1,000 $11,489 $231 $1,061 +$44
RW1 Rainwater tanks 300 $64,942 Nil $11,044 +$140
E2 IPR 2: Membrane system treating 3,300 $57,860 $4,302 $2,168 +$318 10 ML/day
R1 Lake Rowlands 972 $84,500 $576 $5,597 +$246
(1) The calculation of TRB assumes the option is implemented within expected timeframes commencing 2010/11. These values are different to those presented at the PRG Meeting 3 due to changes in the way the residential TRB is calculated. The relative performance of each option remained the same. Likewise there have been slight changes in the capital and operating costs as assessment of each option is refined. (2) Includes $18.2 million grant. Change in TRB without grant is $256 per assessment. (3) The secure yield of the Burrendong pipeline option is different to that presented at PRG Meeting 3 (where it was 3,400 ML/year). Modelling of this option was adjusted to reduce the annual operating costs and make it comparable in a secure yield sense to the Macquarie River to Orange pipeline option.
4.4.4 EVALUATION OF SHORT LISTED OPTIONS
Orange City Council has adopted a Quadruple Bottom Line (QBL) process to assist with identifying preferred options. This process is the same as Triple Bottom Line (TBL) assessment, but includes one extra criterion: governance.
The process involves identifying the best value for money after taking account of the social, environmental, governance and economic considerations. The evaluation method presented in the following sections assists the decision making process by indicating the relative merits of each scheme.
4.4.4.1 Environmental, Social and Governance Performance
The environmental, social and governance performance of each scheme was estimated using criteria developed through the IWCM consultation process. The process involved: • Selecting criteria for each of the environmental, social and governance impacts (PRG Meeting 2); • Assigning a weighting representing the relative importance of each criteria for each of the environmental, social and governance impacts (PRG Meeting 3); • Assigning a relative performance score for each criterion for each scheme (PRG Meeting 3); and • Calculating the total weighted performance and then the total environmental, social and governance score (ESGS).
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The process of undertaking the QBL involves: • Scoring the criterion (using a 1 to 5 rating – 1 is least important; 5 is critical indicator) to obtain criteria weightings; • Scoring each option against the criterion using a score of 0 to 10 (1 = worst; 10 = best); and • Summing the weight scores to provide an Environmental, Social and Governance score (ESGS); and • Dividing the ESGS by the Net Present Value of the option to obtain a final score and ranking.
The assessment methodology is consistent with the NSW Office of Water’s method for the evaluation of IWCM scenarios (NSW Office of Water, 2010).
Scoring of the criterion and options was done through consensus at the PRG meetings.
The criteria were as derived from the PRG Meeting 2 (December 2010). During the process two criteria were removed from the analysis as follows: • Equity and acceptability (social criteria); and • Ability to commit to scheme in business model (governance criteria).
Criteria that could be quantified were assessed by scaling the relevant measure between 1 and 10 on a linear basis. This was done for: • Security and reliability of urban water service (used increase in secure yield); • Level of service (used increase in secure yield); • Carbon (GHG emissions); and • Change in TRB.
4.4.4.2 Economic Evaluation
The Net Present Value (NPV) of capital and operating costs were determined for each scheme (refer to Section 3).
4.4.4.3 Results
The final QBL results from PRG Meeting 3 are attached as Appendix D.
The ranking from the environmental, social and governance scores was: 1. Longer restriction periods;
2. IPR membrane plant;
3. Burrendong pipeline; 4. Rainwater tanks;
5. BSC Stage 36;
6. Mulyan Creek dam; and 7. Lake Rowlands.
6 The Draft Water Sharing Plan prohibits licensing of the proposed Stage 3 weir without Ministerial consent. This was not known at the time of PRG Meeting 3.
PAGE 136 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
Overall QBL ranking was:
1. Longer restriction periods;
2. BSC Stage 36;
3. Rainwater tanks;
4. Mulyan Creek Dam; 5. Burrendong pipeline;
6. IPR membrane plant; and
7. Lake Rowlands.
Key messages from the QBL were: • Dams (Mulyan and Rowlands options) did not score well from an environmental, social and governance perspective; • The demand management measure (with no cost) will always come out as the highest ranked option; and • High cost options such as IPR and Burrendong pipeline are lower in the ranking, although they score relatively well in against the ESG criteria.
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Conclusions and Recommendations
5.1 CONCLUSIONS
This report presents a review the various water sources considered by Orange City Council to provide long term water security including: surface water, stormwater, rainwater, groundwater, treated effluent, regional supplies, other emergency solutions and demand management. Thirty five potential water supply options were considered. Six of these options are included in Council’s BAU scenario: • bores adding 462 ML/year; • Ploughmans Creek stormwater harvesting scheme operating on a 100% trigger; • full licensing of Blackmans Swamp Creek Stage 1 (i.e. operating on a 100% trigger); • raising Suma Park Dam by 1.0 m in conjunction with dam safety upgrade works; • the Macquarie River to Orange pipeline; and • Blackmans Swamp Creek Stage 2 stormwater harvesting.
Secure yield modelling of the BAU scenario shows that the proposed BAU water supply infrastructure components provide water security for 50 years. Even under climate change assumptions, the BAU water supply infrastructure components provide water security for at least the next 30 years. It is therefore concluded that the BAU actions will address the IWCM target of providing water security in accordance with the 5/10/10 secure yield rule.
BAU water supply components are subject to gaining the required environmental approvals and licences. During this process the scope of the component may change, or indeed, it may not gain approval. In this case other options would need to be investigated.
The long list of water supply options was screened to develop a short list of seven. These were considered by the PRG using a Quadruple Bottom Line (QBL) process to identify the relative merits of each scheme. The overall QBL ranking was: 1. Longer restriction periods 2. BSC Stage 3; 3. Rainwater tanks; 4. Mulyan Creek Dam; 5. Burrendong pipeline; 6. IPR membrane plant; and 7. Lake Rowlands.
It is considered that the short listed options and the QBL process has identified the preferred options that should be considered next if elements of the BAU do not eventuate
5.2 RECOMMENDATIONS
It is recommended that: • The information in this report is used to inform future IWCM reviews; • This information is updated as further data or options become available; and • The identified short list is used to identify alternate sources if elements of the BAU scenario do not eventuate.
PAGE 138 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
References
Cloke P (undated) Notes on secure yield. Unpublished paper.
C M Jewell & Associates (2004a) Groundwater sampling, Reform shaft, Lucknow, New South Wales. Report prepared for Orange City Council.
C M Jewell & Associates (2004b) Groundwater Supply Investigation, Orange. Report prepared for Orange City Council.
C M Jewell & Associates (2008) Review of Groundwater Assessment, Orange. Report prepared for Orange City Council.
C M Jewell & Associates (2009a) Overview of potential hydrogeological and geotechnical issues relating to the extraction of water from the former Lucknow Mine, New South Wales. Report prepared for Orange City Council.
C M Jewell & Associates (2009b) Orange Basalt Groundwater Resources. Report prepared for Orange City Council.
C M Jewell & Associates (2009c) Hydrogeological Assessment, North Orange. Report prepared for Orange City Council.
C M Jewell & Associates (2011) Feasibility study Managed Aquifer Recharge. Report prepared for MWH.
Department of Commerce (2008) Browns Creek Mine Water Supply to Orange. Transfer system desk top study. Report prepared for Orange City Council.
Entura (2011a) Suma Park Dam Upgrade – Concept Design Report. Report prepared for Orange City Council.
Entura (2011b) Suma Park Dam Upgrade – Options Assessment for Raising FSL. Report prepared for Orange City Council.
Department of Energy, Utilities and Sustainability (2006) Integrated Water Cycle Management Demand Side Management Decision Support System - Simplified (Version S1.1). New South Wales Government.
Department of Energy, Utilities and Sustainability (2006) Integrated Water Cycle Management Rainwater Tank Model (Version RTM 2.1) Manual. New South Wales Government.
Geolyse Pty Ltd (2007) Spring Creek Dam De-silting – Preliminary Feasibility Assessment. Report prepared for Orange City Council.
Geolyse Pty Ltd (2008a) Review of Environmental Factors Blackmans Swamp Creek Stormwater Harvesting Scheme. Report prepared for Orange City Council.
Geolyse Pty Ltd (2008b) Blackmans Swamp Creek Stormwater Harvesting Scheme – Revised Harvesting Weir Operational Plan. Report prepared for Orange City Council.
Geolyse Pty Ltd (2009a) Review of Environmental Factors Gosling Creek Reservoir – Water Transfer. Report prepared for Orange City Council.
Geolyse Pty Ltd (2009b) Review of Environmental Factors Ploughmans Creek Stormwater Harvesting Scheme. Report prepared for Orange City Council.
Geolyse Pty Ltd (2011) Technical Note 5 - Options for Reticulated Alternative Water Supply in the PVNO Area. Report prepared for Orange City Council.
Geolyse Pty Ltd (2012) Macquarie River to Orange pipeline project – Hydrology and water security assessment. Report prepared for Orange City Council.
Gilbert & Associates Pty Ltd (2009) Cadia East project surface water assessment. Report prepared for Cadia Holdings Pty Limited.
Government of NSW (2002) Advice to water management committees. No. 6 daily extraction management in unregulated rivers (2002 version). NSW Government.
Hunter Water Australia (2006) Orange Wastewater Treatment Plant Storm Storage Feasibility Study. Report prepared for Orange City Council. http://greenhousegas.nsw.gov.au/documents/FS-Comp-PoolCoeff-Oct11.pdf http://www.statewater.com.au/_Documents/Dam%20brochures/Burrendong%20Dam%20brochure.pdf
IBL Solutions (2009) Orange City Council Report on Development of Alternative Water Supplies. Report prepared for Orange City Council
IBL Solutions (2011) An update on indirect potable reuse. Report prepared for Orange City Council.
PAGE 139 OCC_IWCM_TECHNICAL NOTE 2_FINAL.DOCX TECHNICAL NOTE 2 ORANGE WATER RESOURCES ORANGE CITY COUNCIL
MWH (2007) Orange Integrated Water Cycle Management Concept Study. Report prepared for Orange City Council.
MWH (2009) Centroc water security study component 2: Options paper
MWH (2010) Emergency Water Supply Further Feasibility Assessment. Report prepared for Orange City Council.
MWH (2011a) Emergency Water Supply Concept Report. Report prepared for Orange City Council.
MWH (2011b) Business Case Managed Aquifer Recharge. Report prepared for Orange City Council.
NSW Water Solutions (2009) Orange Water Supply Scheme Water Cartage Contingency Plan Options.
NSW Office of Water (2010) Information Sheet 6: Evaluation of IWCM Scenarios.
NSW Office of Water (2011) Draft Water Sharing Plan for the Macquarie Bogan Unregulated and Alluvial Water Sources.
Orange City Council (2009) Water projects update report – November 2009. Report to Council Meeting – 19 November 2009. 2009/1066.
Orange City Council (2010) Water strategy update report – December 2010. Report to Council Meeting – 2 December 2010. 210/1233.
Orange City Council (2011) Orange emergency drought connection Macquarie pipeline update. Report to Council Meeting – 18 August 2011. 2011/791.
Samra S and Cloke P (2010) “NSW Response for Addressing the Impact of Climate Change on the Water Supply Security of Country Towns.” Proceedings of Practical Responses to Climate Change, National Conference 2010, 29 September - 1 October 2010 Melbourne. Institution of Engineers, Australia.
SMEC (2003) Suma Park Dam Augmentation Environmental Impact Statement. Report prepared for Orange City Council, Ministry of Energy and Utilities and NSW Department of Commerce.
Swan Environmental (2011) Water Security Options – Water from Lake Canobolas. Report prepared for Orange City Council.
Watts Dr P J (2005) Scoping study – reduction of evaporation from farm dams. Final report to the National Program for Sustainable Irrigation. Feedlot Services Australia Pty Ltd, Toowoomba.
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Appendix A QUOTE FOR RAINWATER TANK INSTALLATION
PO Box 8524, East Orange NSW 2800 Shed 3, 37 Peisley Street, ORANGE NSW 2800
atf SD & NK Adams Family Trust Phone: 02 6363 1445 Fax: 02 6363 1446 [email protected] ACN 124 639 130 ABN 53 925 411 704
Estimate #354 2 December, 2011
Orange City Council PO Box 35 Orange NSW 2800
Attn: Wayne Beatty Fax: 02 6393 8199
WATER TANK INSTALL ESTIMATE – WITH PUMP AND CHARGED LINES
We are pleased to submit this estimate to supply and install either a 5,000L or 10,000L rain water tank (standard height Bushmans tank), one Onga Rainband pump (S-MHW450C) including hook up to town water supply, allowance of two downpipe installs (through a charged stormwater system), a first flush diverter and two garden taps on outlet side. 10,000L Tank Labour and Materials: 6,295.00 629.50 (GST) $6,924.50
5,000L Tank Labour and Materials: 5,825.00 582.50 (GST) $6,407.50
Any services hit during excavation will be charged to the client. Price does not include any concrete cutting or removal of pathways. Maximum stormwater run is approximately 24 meters and maximum tap pipework is also 24 meters. New downpipes will be in PVC. Price down not include any painting or electrical works. NB: one outdoor GPO will be required for pump. Pump cover is included in this price. Price does not include any leaf catchers. Price does not allow for turf or re- seeding. This price has no allowance for crane hire if tank access in restricted. - 2 -
Town water will be required during commissioning stage. Price allows for level surface area for tank placement. If you have any questions regarding this report, or require further information, please do not hesitate to contact me on my mobile 0411 128 088.
Yours sincerely,
Steve Adams STEVE ADAMS PLUMBING PTY LTD
PO Box 8524, East Orange NSW 2800 Shed 3, 37 Peisley Street, ORANGE NSW 2800
atf SD & NK Adams Family Trust Phone: 02 6363 1445 Fax: 02 6363 1446 [email protected] ACN 124 639 130 ABN 53 925 411 704
Estimate #355 2 December, 2011
Orange City Council PO Box 35 Orange NSW 2800
Attn: Wayne Beatty Fax: 02 6393 8199
WATER TANK INSTALL ESTIMATE – WITHOUT PUMP OR CHARGED LINES
We are pleased to submit this estimate to supply and install either a 5,000L or 10,000L rain water tank (standard height Bushmans tank) adjacent to the house and feed tank with one aerial downpipe (through a first flush diverter) and return overflow to existing stormwater supple and supply one gravity fed tap – with maximum of 5m pipework. 10,000L Tank Labour and Materials: 3,320.00 332.00 (GST) $3,652.00
5,000L Tank Labour and Materials: 2,790.00 279.00 (GST) $3,069.00
Price allows for level surface area for tank placement. Price does not include any painting works. Price does not include any leaf catchers. This price has no allowance for crane hire if tank access is restricted. Town water will be required during commissioning stage. If you have any questions regarding this report, or require further information, please do not hesitate to contact me on my mobile 0411 128 088. - 2 -
Yours sincerely,
Steve Adams STEVE ADAMS PLUMBING PTY LTD
Appendix B IBL SOLUTIONS REPORTS
ORANGE CITY COUNCIL An Update on Indirect Potable Reuse
6 October 2011 Ian Law IBL Solutions
2 IBL Solutions
ORANGE CITY COUNCIL
REPORT ON DEVELOPMENT OF ALTERNATIVE WATER SUPPLIES
1. Introduction
Ian Law of IBL Solutions submitted a report in November 2009 on a preliminary assessment of alternative water supplies for Orange. This report covered:
A raw water scheme for outdoor and toilet flushing use only; Package plant treatment of bore water for injection into the potable supply system; A third pipe system for new developments for outdoor and toilet flushing use only, and An indirect potable reuse scheme.
Indicative capital and annual operating costs for the schemes were developed, based on flow and quality data provided by Orange City Council staff.
The last option, Indirect Potable Reuse (IPR), was further discussed at a meeting in Orange on 29 September 2011 and an update on this option together with associated costs was requested.
2. IPR applications and technologies involved
2.1 IPR Applications
An indirect potable reuse (IPR) scheme entails advanced treatment of a municipal wastewater treatment plant (WWTP) effluent to a very high standard, with this reclaimed water then being transported to a dam, in which it mixes with raw water and then is further treated in a water treatment plant (WTP) before distribution to the community.
The advanced treatment stage must address both the ‘acute’ and the ‘chronic’ risks associated with introducing a reclaimed water into a drinking water supply.
There are many examples of schemes that produce a potable quality of water from a municipal WWTP around the world – in Europe, the US, South Africa, Namibia and Singapore.
IPR has been considered in Goulburn, NSW, the Australian Capital Territory, South Caboolture and Toowoomba, both in Queensland. The need for the IPR project in Goulburn was obviated by the NSW’s government decision to construct a water transfer pipeline instead; the IPR project for the ACT did not proceed past the planning study while that proposed for South Caboolture was constructed but not implemented. In the case of Toowoomba, the project moved through the planning phase and attracted
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support from the Australian Government for $22.9m of the $67.8m total project cost, subject to community support in a referendum. However, the community voted 61% to 38% against the project and the IPR project was abandoned.
The only IPR project that has been built in Australia to date is the Western Corridor Recycled Water Scheme in South East Queensland that produces drinking quality water suitable for release into the Wivenhoe dam, Brisbane’s principal water storage. The $2.6 Billion scheme consists of three advanced water treatment plants located at Bundamba, Gibson Island and Luggage Point which draw feedwater from six nutrient removal wastewater treatment plants. Each of the three water recycling plants incorporate microfiltration (MF) and reverse osmosis (RO) followed by an advanced oxidation system using ultraviolet light and hydrogen peroxide to remove specific disinfection by-products and non- specific low molecular weight organics.
The residual brine stream from the Bundamba advanced water treatment plant is nitrified and denitrified to reduce nitrogen concentrations before discharge into the Brisbane River that flows to Moreton Bay. The project has a production capacity of 232 ML/d, over 200km of interconnecting and product water delivery pipelines and was delivered using 5 fast track alliances over a 2 year period.
However, a perceived reduction in public support for IPR prior to Queensland’s November 2008 election resulted in the introduction of policy by the State Government not to augment drinking water supplies until dam levels fall below 40%. The Scheme is currently operating at reduced capacity supplying reclaimed water to two major power stations.
In Western Australia, the Water Corporation is operating a demonstration project investigating the feasibility of reclaiming water from the Beenyup WWTP using membrane filtration, reverse osmosis and UV disinfection prior to injection into the Leederville aquifer. If successful a full-scale facility could provide an additional 1.5GL/a supply to the aquifers supplying Perth’s drinking water.
The technologies that are used in such potable reuse schemes have all been applied in Australia. The membrane systems are now well proven as are the ozone/activated carbon alternatives – the latter processes having been installed at a number of installations in Australia on municipal WWTP effluents; South Caboolture and Dalby in Queensland, Gerringong-Gerroa in NSW would be good examples of operational plants. Melbourne Water is currently augmenting its 800 ML/d Eastern Treatment Plant with the ozone/activated carbon technology with completion due by the end of 2012.
2.2 IPR Treatment Trains
The primary treatment objectives for IPR plants are the removal of pathogens and organics by implementing a multiple-barrier treatment process or train that typically includes some of the following technologies: coagulation and sedimentation for particle and organics removal, filtration (conventional or membranes) for particle and pathogen removal, reverse osmosis (RO) or granular
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activated carbon (GAC) for organics removal, advanced oxidation (AOP) for removal of micro- contaminants and disinfection for inactivation of pathogens.
Examples of two treatment trains that find application in such schemes are shown in Figures 1 and 2 below. Both Figures show the reclaimed water being discharged into a surface reservoir before being further treated in a conventional water treatment plant (WTP). It should be noted that these two treatment trains are indicative only – detailed design may well show that different unit process combinations may be more appropriate. For example, it may be more appropriate to install an Ultrafiltration (UF) stage after the Granular Activated Carbon (GAC) stage rather than install the Chemical Clarification stage in the Figure 1 train.
The treatment train shown in Figure 1 is ideal for inland plants as it does not produce a sidestream (the concentrate flow from the reverse osmosis step in the train shown in Figure 2) but it will not produce a reclaimed water with as low an organic content – in terms of total organic carbon (TOC) – as the train in Figure 2.
The treatment train shown in Figure 2 relies on membrane systems followed by an advanced oxidation. The concentrate from the RO – which can amount to some 15-25% of the flow to the RO unit – is generally disposed of to the ocean in the case of coastal cities while evaporation basins, deep well injection or concentration followed by crystallization (the Zero Liquid Discharge (ZLD) option) are considered for inland locations.
Figure 1: IPR Treatment Train without Membranes
Figure 2: IPR Treatment Train with Membranes
3. Cost Estimates
The cost estimates prepared for the IPR option have been based on the following:
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A WWTP effluent feed flow of 10 ML/d;
The pumpstation and pipeline required to transfer the reclaimed water to Suma Park Dam are not included;
All associated non-construction costs, including contingencies, are not included.
Table 1 summarises the capital cost estimates for an 10 ML/d plant with two different configurations; one as per Figure 1 and the second as per Figure 2 but including a Zero Liquid Discharge (ZLD) treatment system for the brine or concentrate flow from the RO unit.
Table 1: Summary of capital Cost Estimates
Item Non-Membrane Membrane System System (Figure 1) (Figure 2) + Brine Treatment (ZLD)
Capital Cost ($M) 22 55
$M/ML feed 2.2 5.5
Table 2 summarises the annual operating costs for the two systems presented in Table 1 above, with the costs presented including for labour, maintenance, membrane replacement (in the case of the Figure 2 train), spent carbon regeneration (in the case of the Figure 1 train), chemicals, and power – capital is excluded.
Table 2: Summary of Annual Operating Cost Estimates
Item Non-Membrane Membrane System System (Figure 1) (Figure 2) + Brine Treatment (ZLD)
Annual Operating Cost 4.4 3.9 ($M/annum)
Daily Flow of Reclaimed 9.4 9.1 Water (ML/d) to Dam
$/kL product 1.3 1.2
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The Table shows that the non-membrane option has the highest annual operating cost, but if the GAC regeneration reduces to once a year in lieu of the assumed three times a year, the annual operating cost of this option reduces to $0.6/kL product or $2.1M/annum.
3.1 Operating Cost Make-up
An indication of the percentage split of the operating cost for the Membrane + ZLD treatment train (Figure 2) would be:
Labour : 6% Power : 19% (typically 1.9kWh/kL) Chemicals : 20% Maintenance : 45% Others : 10% (membrane replacement, laboratory analyses, lamp replacement etc)
A make-up for the non-membrane option is more plant specific and can only be established through a more detailed design assessment.
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ORANGE CITY COUNCIL Report on Development of Alternative Water Supplies
1 November 2009 IBL Solutions
2 IBL Solutions
ORANGE CITY COUNCIL
REPORT ON DEVELOPMENT OF ALTERNATIVE WATER SUPPLIES
1. Introduction
Ian Law of IBL Solutions was appointed to provide a brief overview and comparison of the levels of treatment that would be required to achieve the following reuse applications for the City of Orange in the future:
A raw water scheme for outdoor and toilet flushing use only; Package plant treatment of bore water for injection into the potable supply system; A third pipe system for new developments for outdoor and toilet flushing use only, and An indirect potable reuse scheme.
In addition, indicative capital and annual operating costs for the schemes are to be developed, based on flow and quality data provided by Orange City Council staff.
The Report discusses levels of treatment required for each of the schemes before presenting the cost estimates.
2. Level of Treatment
The development of any water supply scheme must follow the guidelines set out in the Australian Drinking Water Guidelines and the Australian Guidelines for Water Recycling, in that the level of treatment must be considered within a risk management framework that takes into account the quality of the raw water and the intended end use, be it for drinking or solely for outdoor and toilet use.
The risks addressed by the Guidelines are in two categories – ‘acute’ which are short term risks that are associated with microorganisms such as bacteria, viruses and protozoa and ‘chronic’ which are long term, carcinogenic risks and are associated with a range of organic micro‐contaminants.
This risk assessment requirement can be a long process and given that this report has to be produced in a very short timeframe, the level of treatment discussed for each of the four schemes is based on the following considerations:
The format of similar schemes elsewhere in Australia and overseas that have met with relevant Regulatory approval, and
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The experience of the author.
2.1 Raw Water Scheme
The level of treatment required for a raw water domestic non‐potable scheme is generally based on turbidity and pathogen removal and in the event of the raw water being shown to be corrosive to concrete lined pipes, it may be necessary to implement a degree of stability correction to the water by means of lime or caustic addition.
A typical treatment train would be:
Conventional filtration Disinfection (chlorination), and pH adjustment using lime or caustic.
It should be noted that a raw water scheme for non‐potable purposes will not necessarily lead to any reduction in overall water usage by consumers and as such this option does not fall into the alternative water supply category. Essentially all that is being achieved is a reduced level of treatment, and hence reduced annual operating cost, for a portion of the daily extract from the same raw water source that is then used for domestic non‐potable purposes.
2.2 Bore Water Scheme
The level of treatment required for direct injection of bore water into the potable supply system will depend on the following quality factors:
Total dissolved solids (TDS); Hardness pH and alkalinity Iron – both soluble and suspended Microbial content
The quality of the water to be injected must, as a minimum, comply with the requirements of the Australian Drinking Water Guidelines (ADWG). However, consideration must also be given to the quality of the water into which the bore water is to be injected so as to avoid quality variation at the consumer taps when the bore water is introduced.
Ignoring this latter consideration for the moment, and assuming that the bore water exceeds the ADWG for hardness (in the ‘temporary’ form) and iron content and that it also occasionally contains a presence of pathogens, a typical treatment train would be:
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Aeration (to precipitate iron) Lime softening Conventional filtration Disinfection (chlorination), and possibly pH control
In the event of the bore water also having TDS at levels above that of the drinking water, then the treatment train will be built around a salt reduction stage which could be either nano‐filtration (NF) or reverse osmosis (RO). Incorporation of these membrane systems will simplify the overall train as they will also remove hardness and iron but the disinfection and pH adjustment stages will still be required.
These salt removal technologies will give rise to a saline concentrate that could amount to some 10‐ 15% of the total feed flow and this in turn will have to handled and disposed of in a responsible manner.
Bore water yields are generally such that small package treatment plants are appropriate forms of treatment.
It should be noted that these treatment trains could be simplified if the bore water was not to be introduced directly into the drinking water distribution system but rather into the Suma Park Dam where it would blend in with the raw water. A further advantage of this point of discharge is that of risk management, in that any sub‐quality water produced by the package plants due to equipment malfunction is further treated not only in the Dam but also in the Water Treatment Plant.
Discharge of the bore water to the stormwater harvesting scheme and then to the Dam would add a further treatment barrier to the overall scheme.
2.3 Third Pipe System
The level of treatment required for third pipe systems for new development areas is generally only associated with minimizing the acute risk to health of the customers in the houses or on the properties.
NSW was the first State in Australia to publish a set of guidelines for domestic non‐potable reuse – in 1993. These Guidelines were based on the Californian Title 22 Standards in that they outlined an acceptable treatment train as a means of ensuring the supply of reclaimed water that would minimize the acute risk to consumers.
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The ‘approved’ treatment train for a municipal WWTP effluent, as outlined in the 1993 Guidelines, is chemical clarification, dual media filtration and free chorine disinfection. With the introduction of the Australian Guidelines for Water Recycling in 2006 and the rapid development in membrane systems, most third pipe systems installed in recent times in Australia incorporate a membrane filtration stage in lieu of the conventional filtration stage as well as, in most cases, the upfront chemical clarification stage, followed by an ultraviolet light (UV) disinfection stage.
A typical advanced treatment plant for achieving a reclaimed water of suitable quality for a third pipe system can be summarized as shown in Figure 1 below.
Figure 1: Typical Treatment Train for Third Pipe System
WWTP Effluent Membrane UV Chlorination Filtration Disinfection
This development in membrane systems has also spawned a new biological treatment technology, the ‘membrane bioreactor (MBR)’, that uses either MF or UF membranes and replaces the more conventional activated sludge system for the treatment of municipal wastewaters. The MBR is a very compact system and produces a secondary effluent that is vastly superior to that produced by the conventional plants.
The development of the MBR technology has opened the door for ‘sewer mining’ applications within the urban area; be it for open area irrigation or indeed for providing water to office buildings for toilet flushing and/or fire fighting facilities. The compact nature of the membrane plant, together with the fact that all residuals and by‐ products are returned to the main trunk sewer, means that the actual plant can be located out of sight and/or completely covered. This development is receiving increasing attention around the world, including Australia where a recent example of the application is the plant located in the Botanic Gardens in Melbourne.
Third pipe systems are being installed in many parts of Australia, with Victoria and Queensland leading the way in this regard. Many lessons have been learnt since the first system was installed at Rouse Hill in Sydney in 1990 with perhaps the most salient ones being:
Introducing the Third Pipe System: Third pipe systems are generally not retrofitted to existing developments on account of costs but are considered for new developments, with the additional costs being included in the head works charges that the developers pay. It is an expensive option, with the distribution system generally making up the major portion of the capital cost.
Reclaimed Water Pricing:
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Pricing must be such that use of the water is not excessive, leading to demand exceeding supply and the provider having to ‘top up’ with potable water.
Cross‐Connections: Special plumbing regulations are often promulgated to ensure that cross‐connections between the third pipe and potable water systems are avoided by only allowing skilled plumbers to carry out the internal house plumbing; but they do still occur – Rouse Hill and Newington in Sydney are prime examples of this. Identification of cross connections can only be discovered through a programme of regular audits of each house connected to the third pipe system and this can be a significant cost to the provider.
Aesthetic Quality: Users of these systems often complain about the ‘colour’ of the reclaimed water in the toilet bowl and indeed, there have also been complaints over ‘smell’ in some locations. While these complaints are by no means widespread or ‘deal breakers’, they do take time to resolve.
2.4 Indirect Potable Reuse
An indirect potable reuse (IPR) scheme entails advanced treatment of a municipal wastewater treatment plant (WWTP) effluent to a very high standard, with this reclaimed water then being transported to a dam, in which it mixes with raw water and then is further treated in a water treatment plant (WTP) before distribution to the community.
The advanced treatment stage must address both the ‘acute’ and the ‘chronic’ risks associated with introducing a reclaimed water into a drinking water supply.
There are many examples of schemes that produce a potable quality of water from a municipal WWTP around the world and now in Australia with the Western Corridor Scheme in Brisbane. The oldest potable reuse scheme is that in Windhoek, Namibia that has been operational since 1968.
The primary treatment objectives for IPR plants are the removal of pathogens and organics by implementing a multiple‐barrier treatment process or train that typically includes some of the following technologies: coagulation and sedimentation for particle and organics removal, filtration (conventional or membranes) for particle and pathogen removal, reverse osmosis (RO) or granular activated carbon (GAC) for organics removal, advanced oxidation (AOP) for removal of micro‐ contaminants and disinfection for inactivation of pathogens.
Examples of two treatment trains that find application in such schemes are shown in Figures 2 and 3 below. Both Figures show the reclaimed water being discharged into a surface reservoir before being further treated in a conventional water treatment plant (WTP).
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The treatment train shown in Figure 2 is ideal for inland plants as it does not produce a sidestream (the concentrate flow from the reverse osmosis step in the train shown in Figure 2) but it will not produce a reclaimed water with as low an organic content – in terms of total organic carbon (TOC) – as the train in Figure 3.
The treatment train shown in Figure 3 relies on membrane systems followed by an advanced oxidation. The concentrate from the RO – which can amount to some 15‐25% of the flow to the RO unit – is generally disposed of to the ocean in the case of coastal cities while evaporation basins, deep well injection or concentration followed by crystallization are considered for inland locations.
Figure 2: IPR Treatment Train without Membranes
Figure 3: IPR Treatment Train with Membranes
3. Cost Estimates
The cost estimates presented in this Section of the Report are indicative only but should be adequate to identify the likely range of costs for the various options.
3.1 Raw Water Scheme
As mentioned in Section 2.1 above, the raw water scheme for domestic non‐potable purposes will not reduce overall water consumption or indeed serve as an alternative water source. While it will incur reduced operating cost due to the level of treatment not being as extensive as that that already exists to produce the drinking water in Orange, it will incur additional capital expense for the raw water distribution system to the new developments – much as the third pipe system also does.
As mentioned in Section 2.1 above, treatment will comprise conventional filtration, disinfection and pH adjustment.
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The capital cost estimate for this train for a flow of 8.5 ML/d is $3.5M and to this must be added the cost of the distribution system. The annual operating cost estimate, excluding capital, is $0.37M/annum ($0.12/kL).
3.2 Bore Water Scheme
Orange CC staff have indentified three bores that could be connected directly to the drinking water distribution system; Clifton Grove, Showground and Emu’s. Each is estimated to have a safe yield of some 0.5 ML/d, giving rise to a total flow of 1.5 ML/d being available for the drinking water supply from the three bores. Note that if a salt reduction system such as NF or RO is required (refer to Section 2.2 above) then the volume of water injected into the distribution system will reduce to some 1.3 ML/d.
Indicative quality of the water the Clifton Grove and Showground bores is summarized in Table 1 below and that of the drinking water is included for comparison. Emu is not included as the quality data for this bore was not available at the time of compiling this report.
Table 1: Comparison of Bore Water with Drinking Water
Parameter Clifton Grove Showground Drinking Water (Average) (Average) (average)
pH 7.0 7.0 7.7
Turbidity (NTU) ‐ 2.55 <0.001
TDS (mg/L) 260 355 110
Total Hardness 140 313 78
(mg/L as CaCO3)
Iron (mg/L) 1.5 0.24 0.03
Manganese (mg/L) 2.3 0.02 0.001
Total Coliforms <1 74 2 (MPN/100 mL)
n/a = not available
The table shows that it will be necessary to remove salt if the bore water is to be injected directly into the drinking water distribution system and thus the treatment plant will include either an NF or a RO stage, in addition to disinfection and pH adjustment (refer to Section 2.2 above). Pretreatment for either of the membrane systems will be by conventional sand filtration followed by cartridge filtration.
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The capital cost estimate for such a plant for a flow of 0.5 ML/d is $1M while the operating cost (excluding capital) is $0.18M/annum ($0.38/kL, assuming that the concentrate stream form the NF or RO stage is collected and tinkered away for separate disposal).
3.3 Third Pipe System
Orange CC staff estimate that the third pipe system should cater for some 4,500 new house connections, which with a demand of 1,500 L/d/household equates to a flow of 6.8 ML/d of reclaimed water to use outdoors and for toilet flushing.
As it may take some time for all the 4,500 new houses to be built, it would be appropriate to stage the construction of the advanced treatment plant in an attempt to balance demand with supply as well as cash flow.
The cost estimate has been based on the following:
construction of a plant for a reclaimed water flow of 3.5 ML/d that will in itself be modularized and capable of being readily expanded to the full 6.8 ML/d as demand increases;
the cost of the pump station and transfer pipework are excluded as they will be developed by Council staff, and
the treatment train will comprise membrane filtration followed by UV disinfection and chlorination (the latter in order to maintain a residual in the distribution system) – Figure 1 refers.
The Capital cost of the proposed treatment train that is sized for 3.5 ML/d and which is expandable to 6.8 ML/d is $2.6M, with the annual operating cost (excluding capital) being $0.18M ($0.15/kL of reclaimed water produced).
3.4 Indirect Potable Reuse
The cost estimates prepared for the IPR option has been based on the following:
A WWTP effluent flow, of the quality summarized in the spreadsheet forwarded on 21 October, of 8.5 ML/d;
The pumpstation and pipeline required to transfer the reclaimed water to Suma Park Dam have been excluded and will be prepared by Orange CC staff;
Costs of similar projects from around the world and recently from within Australia, noting that costs of specialty pipe material has increased by some 30‐40% over the last few years.
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Table 2 summarises the capital cost estimates for an 8.5 ML/d plant with three different configurations; two with the membranes (as per Figure 2) but with one including a Zero Liquid Discharge (ZLD) treatment system for the brine or concentrate flow from the RO unit and one without the membranes (as per Figure 2) and with four regenerations of the GAC per year.
It will be appreciated that the volume of reclaimed water produced by the non‐membrane train will be greater than that produced by the membrane based train – due to the concentrate produced from the RO system in the latter train. This flow could vary from 1.25 to 2.15 ML/d and will be dependent upon the actual design of the RO system. It could also have an impact on the cost of the transfer system up to Suma Park Dam.
Table 2: Summary of capital Cost Estimates
Item Non‐Membrane Membrane System Membrane System + System (Figure 2) (Figure 3) Brine Treatment (ZLD)
Capital Cost ($M) 14.45 19.55 37.40
$M/ML feed 1.7 2.3 4.4
Table 3 summarises the annual operating costs for the three systems presented in Table 1 above, with the costs presented including for labour, maintenance, membrane replacement, chemicals, and power – capital is excluded.
Table 3: Summary of Annual Operating Cost Estimates
Item Non‐Membrane Membrane System Membrane System + System (Figure 2) (Figure 3) Brine Treatment (ZLD)
Annual Operating Cost 2.63 0.99 2.11 ($M/annum)
Daily Flow of Reclaimed 8.0 6.8 7.7 Water (ML/d) to Dam
$/kL product 0.90(i) 0.40 0.75
Notes:
(i) This cost reduces to some $0.3/kL if the frequency of regeneration of the GAC is reduced to twice a year in lieu of the four times a year.
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The Table shows that the non‐membrane option has the highest annual operating cost, but if the GAC regeneration reduces to twice a year, the annual operating cost of this option reduces to $0.3/kL or $0.79M.
4. Summary of Costs
A summary of capital and annual operating costs for the four options is presented in Table 4.
Table 4: Summary of Cost Estimates
Option Design Flow (ML/d) Capital Cost ($M) Operating Cost ($M/annum)
Raw Water 8.5 3.5 0.37
Bore Water 1.5 (3x0.5) 3.0 0.18
3rd Pipe System(i) 3.5(ii) 2.6 0.18
IPR – non membrane(iii) 8.5 14. 5 0.9 ‐ 2.6
IPR – membrane(iii) 8.5 19.6 – 37.4 1.0 – 2.1
(i) Excludes the distribution system (ii) 1st stage of a final capacity of 6.8 ML/d (iii) Excludes the transfer pipeline to the dam
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐
Oct 09 Report Page 11
Appendix C CLIMATE CHANGE MODELLING RESULTS
NSW RESPONSE FOR ADDRESSING THE IMPACT OF CLIMATE CHANGE ON THE WATER SUPPLY SECURITY OF COUNTRY TOWNS
Sam Samra 1, Peter Cloke 2 1. Senior Manager, Water Utility Performance, NSW Office of Water Sydney, NSW 2000 [email protected] 2. Principal Hydrologist, NSW Water Solutions, NSW Public Works Sydney, NSW 2000 [email protected]
ABSTRACT Under the NSW Government’s Best-Practice Management of Water Supply and Sewerage Guidelines, local water utilities in non-metropolitan NSW are required to prepare and implement a comprehensive 30-year integrated water cycle management (IWCM) strategy. The IWCM strategy is prepared for the utility’s water supply, sewerage and stormwater businesses, including the water supply headworks, and is effectively a 30-year rolling strategy, which must be reviewed and updated by each utility every 6 years.
For the past 25 years most urban water supply headworks in country NSW have been sized on a robust Security of Supply basis. This security of supply basis has been designed to cost-effectively provide sufficient dam storage capacity to allow the water utility to effectively manage its water supply in future droughts of greater severity than experienced over the past 100 or more years. ‘Secure Yield’ is the water demand that can be expected to be supplied with only moderate water restrictions during a significantly more severe drought than had been experienced historically. The required water restrictions must not be too severe, not too frequent, nor of excessive duration. Recent analysis for the severe 2001-2007 drought has confirmed the continuing robustness of the NSW Security of Supply basis.
To understand the potential impact of climate change on the security of urban water supplies, results are presented from a pilot study for 11 non-metropolitan NSW water supplies utilising 112 years of downscaled daily hydrometeorological data from 15 global climate models for climate change projections for the year 2030 using the A1B medium warming emissions scenario. This analysis enabled determination of the impact of climate change on the Year 2030 secure yield for each water supply.
Future 30-year IWCM strategies in NSW will need to include assessment of the secure yield of the utility’s water supply in accordance with the analysis reported for the pilot study. Implementation of these strategies, together with the required 6-yearly updates, will address future water security.
INTRODUCTION The NSW Government is tackling the challenge of the impact of climate change on non-metropolitan urban water utilities in a multi-pronged approach through comprehensive best practice management requirements, as noted below.
The key element of the NSW response to climate change is that the utilities will be required to determine their urban water supply security along the lines of the analysis reported in this paper for the pilot study for 11 NSW water supplies. Reporting of such water supply security analysis will need to be documented in each utility’s 30-year IWCM strategy.
Background The NSW Government’s Best-Practice Management of Water Supply and Sewerage Guidelines (Dept Water and Energy, 2007) is the key driver for reform of planning and management and performance improvement in non-metropolitan NSW. 106 NSW local water utilities provide piped water supply and sewerage services to the 1.8 million people in NSW country towns (97.9% water supply coverage). The 19 requirements of the guidelines include:
• Annual performance monitoring by each utility; • Current 20 year strategic business plan and financial plan; • Regulation of water supply, sewerage and trade waste (including pay-for-use water pricing, full cost recovery, commercial sewer usage, trade waste and developer charges, trade waste approvals for all dischargers and a sound trade waste regulation policy by each utility); • Demand management; • Drought management ; and S. Samra, P. Cloke • Integrated Water Cycle Management (IWCM) - comprehensive 30 year strategy required for the utility’s water supply, including headworks, sewerage, and where cost-effective, stormwater businesses. A full range of scenarios must be evaluated on a rigorous triple bottom line (TBL) basis, with extensive community involvement. The IWCM Strategy is effectively a 30-year rolling strategy, which must be reviewed and updated by each utility every 6 years.
The non-metropolitan NSW utilities have annual revenue of $950 million and an asset base with a current replacement cost of almost $20 billion (NSW Office of Water, 2010 (1) : vii). Overall, the utilities had met 82% of the requirements of the Best-Practice Management Guidelines by June 2009. The Best-Practice Management Guidelines, the IWCM Guidelines, the 7 IWCM Information Sheets and the annual NSW Water Supply and Sewerage Performance Monitoring Reports and Benchmarking Reports are available on the NSW Office of Water website (www.water.nsw.gov.au).
NSW Security of Supply Basis 45 local water utilities have surface water supplies with storage dams in non-metropolitan NSW. Such utility storages have in the main been sized on the NSW Security of Supply basis since the mid–1980s (NSW Public Works, 1986; Samra & French, 1988 and Cloke, 1995).
The purpose of the NSW Security of Supply basis is to determine the cost-effective storage volume and transfer capacities required to enable each water utility to operate its system with only moderate water restrictions in the event of occurrence of droughts of similar severity to those in the historical record, generally back to at least 1895. The utility would also be able to cope with significantly more severe droughts albeit with more severe water restrictions. Effectively, each water supply system would be able to cope with approximately a ‘1 in 1000 year drought’ (Cloke & Samra, 2009 :13).
Under the NSW Security of Supply basis (commonly referred to as the ‘5/10/20 rule’), water supply headworks systems are normally sized so that: a) Duration of restrictions does not exceed 5% of the time; and b) Frequency of restrictions does not exceed 10% of years (ie. 1 year in 10 on average); and c) Severity of restrictions does not exceed 20%. Systems must be able to meet 80% of the unrestricted water demand (ie. 20% average reduction in consumption due to water restrictions) through a repetition of the worst recorded drought, commencing with the storage drawn down to the level at which restrictions need to be imposed to satisfy a) and b) above.
This enables the utilities to operate their systems without restrictions until the volume of stored water approaches the trigger level determined by a) and b) above (typically about 50% to 60% of the storage capacity). If at this trigger level, the utility imposes drought water restrictions which reduce demand by 20%, the system would be able to cope with a repeat of the worst recorded drought, commencing at that time, without emptying the storage.
‘Secure yield’ is defined as the highest annual water demand that can be supplied from a water supply headworks system while meeting the above ‘5/10/20 rule1’.
The robustness of the NSW Security of Supply basis has been demonstrated by Cloke & Samra (2009 :7) who showed that for the 10 NSW urban water supplies studied, the very severe 2001 to 2007 drought resulted in a reduction in the secure yield of up to 7% for 7 of the water supplies and a reduction of about 15% for the other 3 supplies.
The first paragraph in footnote 2 below2, which is a quote from page 3 of the 2008-09 NSW Water Supply and Sewerage Performance Monitoring Report shows that for the 15 years from 1986, the frequency of drought water restrictions by the non-metropolitan NSW water utilities was consistent with the implied target of no restrictions in 90% of years in b) above.
The 2008-09 NSW Water Supply and Sewerage Benchmarking Report shows each utility’s drought water restrictions over each of the last 6 years (page 56).
1 As noted at the top of page 3, this has been superseded by a ‘5/10/10 rule’ since February 2009. 2 ‘For the 15 years from 1986 to 2000/01, on average, the NSW utilities did not apply any drought water restrictions for 87% of the years, which include the severe 1993 to 1994 drought. This is consistent with the implied target of no restrictions in 90% of years in the NSW Security of Supply basis (commonly referred to as the ‘5/10/10 rule’).
For the 23 years from 1986 to 2008/09, on average, the NSW utilities did not apply any drought water restrictions for 75% of the years. However, this period includes both the above 1993 to 1994 drought and the very severe 2001 to 2008/09 drought.’
S. Samra, P. Cloke The 2008-09 Performance Monitoring Report (page 8) also shows ‘there has been a 47% reduction in the volume of average annual residential water supplied per property in non-metropolitan NSW over the last 18 years (from 330 to 175kL per connected property)’. It is therefore considered that it will now be much more difficult to achieve a 20% reduction in consumption than it was 20 years ago as there has been a large reduction in outdoor water use. Accordingly, in February 2009 the NSW Office of Water agreed to basing future planning in non-metropolitan NSW on being able to achieve an average of only a 10% reduction in consumption through a repetition of the worst drought commencing with the storage already drawn down to satisfy the restriction duration and frequency criteria in a) and b) on page 2. Thus the NSW ‘5/10/20 rule’ has been superseded by a ‘5/10/10 rule’.
Accordingly, a pilot study has been undertaken to examine the impacts climate changed hydrometeorological data has on water security for 11 surface water supplies and to develop a methodology suitable for application for this purpose by the other NSW water utilities.
PILOT STUDY A Climate Change Steering Group has been formed to oversee a climate change pilot study for 11 urban NSW water supplies and development of NSW guidelines for local water utilities on assessing the impact of climate change on the secure yield of their water supplies. The Steering Group members are: • Peter McLoughlin (National Water Commission) • Jai Vaze (NSW Office of Water/CSIRO) • Peter Cloke (NSW Public Works - commissioned to carry out the pilot study) • Sascha Moege (Local Government and Shires Associations) • Wayne Franklin (NSW Water Directorate) • Sam Samra, Mike Partlin, Peter Ledwos (NSW Office of Water)
As indicated above, the purpose of the pilot study was to provide insights on the impacts of climate changed hydrometeorological data on the water security of the 11 water supplies in the pilot study and to then develop a suitable methodology and guidelines for application by the other NSW water utilities.
The pilot study (Samra & Cloke, 2010 :10) involved undertaking hydrological and system modelling to determine the impact of climate change on secure yield. The pilot study incorporates the scientific logic of the CSIRO’s Murray Darling Basin Sustainable Yields Project (Chiew et al, 2008), which used daily historical data from 1895 to 2006 and applied the relevant global climate models (GCMs) to provide projected (~2030) climate changed data for each GCM for this period.
The pilot study uses daily values of rainfall and evapotranspiration from the NSW Office of Water’s 2008 data sets3 (Vaze et al, 2008) for 15 GCMs. These future climate change series for ~2030 were obtained by Vaze et al by scaling the historical 1895-2006 daily rainfall and evapotranspiration data using the methods detailed in Chiew et al ,2008.. These data sets involve extension of the CSIRO data for the Murray Darling basin to cover all of NSW and are based on the Year 2030 A1B warming scenario4; a mid range emissions scenario.
The study essentially involved two modelling steps: • Daily rainfall and evapotranspiration data were inputted into existing calibrated rainfall-runoff models to produce climate changed daily streamflows5 • The daily climate changed streamflows, rainfall and evapotranspiration were inputted into water supply system simulation models6 to determine climate changed secure yields. The climate changed secure yields were compared with the secure yields for a repeat of the historical data set as noted on page 5.
3 This comprehensive data set provides projections of down scaled daily climate changed data for the Year 2030 for all of NSW. It is the best such data set available at present, and was therefore used for the pilot study. As noted on page 10 this data set now covers all of NSW, Victoria and the Murray Darling Basin, including Adelaide. As noted on page 10 improved and longer term projections of climate changed data are expected to be developed in the future and these should be applied by water utilities when they become available. 4 It is noted that there is little difference in the impacts of the various warming scenarios considered by the IPCC for the Year 2030. Such impacts diverge in longer term projections such as for the Year 2050 or 2070. 5 Use of a locally calibrated daily rainfall-runoff model for each water supply is essential. The analysis carried out in the pilot study demonstrated that use of generalised streamflow estimates available from the NSW Office of Water data sets is inappropriate for security of water supply analysis. In NSW, such a local daily rainfall-runoff model is routinely developed for any water supply secure yield study. 6 Similarly, a suitable system simulation model is routinely developed in NSW for any water supply secure yield study. S. Samra, P. Cloke Table 1 lists the 15 GCMs that were used to produce the data sets Table 1: The 15 Global Climate Models Climate Data Series GCM Modelling Group Country 1 CCCMA T47 Canadian Climate Centre Canada 2 CCCMA T63 Canadian Climate Centre Canada 3 CNRM Meteo-France France 4 CSIRO-MK3.0 CSIRO Australia 5 GFDL 2.0 Geophysical Fluid Dynamics Lab USA 6 GISS-AOM NASA/Goddard Institute for Space Studies USA 7 IAP LASG/Institute of Atmospheric Physics China 8 INMCM Institute of Numerical Mathematics Russia 9 IPSL Institut Pierre Simon Laplace France 10 MIROC-M Centre for Climate Research Japan Meteorological Institute of the University of Bonn, Germany 11 MIUB Meteorological Institute of KMA Korea 12 MPI-ECHAMS Max Planck Institute for Meteorology, DKRZ Japan 13 MRI Meteorological Research Institute Japan 14 NCAR-CCSM National Center for Atmospheric Research USA 15 NCAR-PCMI National Center for Atmospheric Research USA
It is noted that to maintain relativity and ensure consistency in the pilot study, modelled streamflow data was used throughout. However in practice in determining 'historical' secure yield, best use is made of the observed data for each utility. Thus the historical estimates in Table 2 differ slightly from the current best estimates of secure yield, which include consideration of the observed data. Thus the Steering Group recommends applying the percentage change in secure yield in column (9) of Table 2 to the utility’s current best estimate of secure yield in order to obtain the climate changed secure yield estimate.
Table 2: Comparison of Secure Yield Estimates# Estimated Secure Yield (ML) % Change in Secure Yield From Historical Data Set Historical Median of Lowest Lowest Median of 15 Lowest GCM Lowest GCM Adopted % Water Data 15 Global GCM GCM GCMs with severity of Change in Year Utility Set* Climate with [(4) – (2)]×100 25% 2030 Secure Models 25% [(3) – (2)]×100 (2) Yield due to (GCMs) severity (2) [(5) – (2)]x100 Climate Change (2) [lesser of (6) & (8)] (%)
(1) (2) (3) (4) (5) (6) (7) (8) (9) 1 21,500 20,000[14] 17,500 [9] 19,500 -7% -19% -9% -9% 2 3,400 3,500 [1] 3,200 [9] 3,600 +3% -6% +6% +3% 3 12,400 12,200 [1] 11,400 [6] 12,600 -2% -8% +2% -2% 4 7,700 7,200 [13] 6,700 [3] 7,200 -6% -13% -6% -6% 5 5,200 4,900 [4] 4,500 [9] 4,800 -4% -13% -8% -8% 6 495 450 [12] 400 [3] 435 -9% -19% -12% -12% 7 4,850 4,150 [4] 3,250 [3] 3,600 -14% -33% -26% -26% 8 3,600 3,600 [8] 2,900 [3] 3,400 0% -19% -6% -6% 9 480 360 [8] 220 [4] 240 -25% -54% -50% -50% 9+ 1500 1260 [7] 880 [4] 1060 -16% -41% -29% -29% 10 185 175 [4] 115 [9] 135 -5% -38% -27% -27% 11 16,900 15,300 [4] 14,300 [13] 15,700 -9% -15% -7% -9% # On the basis of '5/10/10 rule' in ML/a, except for columns (5) and (8), which involve a severity of 25% (ie. a ‘5/10/25 rule’). * 111 years of data (1896 to 2006) from the “Future climate and runoff projections (in 2030) for NSW and ACT” Database. + Enlarged storage for proposed augmentation. In columns (3) and (4), the relevant GCM is shown within square brackets, eg. for Utility 10 the secure yield shown in column (3) is based on GCM 4.
11 Figure 1 shows the general location of the 11 NSW water supply systems examined which covered a range of attributes: large, small, on-stream storage, off-stream storage, coastal, inland and multi-sources.`
Figure 1: Map of NSW showing location of the utilities in the pilot study S. Samra, P. Cloke
RESULTS OF THE PILOT STUDY Climate Change
The projected impacts of climate change in ~2030 on the average annual rainfall, streamflow and evapotranspiration 8 for each utility’s water supply, in comparison with the 4 historical data sets are shown in Figures 2, 3 and 4 respectively. Note that there is a tendency towards drying 0 in NSW. -4 % Change in Rainfall in Change % Following determination of the average annual rainfall for -8 each of the 15 GCMs for each utility, the GCM with the highest average annual rainfall is shown as ‘Highest’ in -12 1 2 3 4 5 6 7 8 91011
Figure 2, expressed as a percentage change in Median Utility comparison with the historical average annual rainfall. Lowest Highest Similarly, the GCM with the lowest average annual rainfall for a utility is shown as ‘Lowest’ and the GCM with the Figure 2: % Change in the Average Annual median average annual rainfall from the 15 GCMs is Rainfall for the Global Climate Models (GCMs) shown as ‘Median’ in Figure 2. shown compared with the result for the Historical Data Set
60 4
40
20 2 0
% Change in Streamflow in Change % -20 % Change in Evapotranspiration in Change %
-40 0 1 2 3 4 5 6 7 8 91011 1 2 3 4 5 6 7 8 91011
Median Utility Median Utility Lowest Lowest Highest Highest
Figure 3: % Change in the Average Annual Figure 4: % Change in the Average Annual Streamflow for the Global Climate Models (GCMs) Evapotranspiration for the Global Climate Models shown compared with the result for the Historical (GCMs) shown compared with the result for the Data Set Historical Data Set
Figure 2 shows that the changes in the average annual rainfall for the GCM with the median change range from no change (Utility 6) to a reduction of 3% (Utility 11) (median is a 2% reduction). For the GCM with the lowest change, the range is reductions of 5% (Utility 3) to 10% (Utility 9) (median is an 8% reduction). For the GCM with the highest change, the range is increases of 3% (Utility 11) to 7% (Utilities 1, 2, 6 and 7) (median is a 5% increase).
Figure 3 shows that the changes in the average annual streamflow for the GCM with the median change range from an increase of 13% to a reduction of 22% (median is a 7% reduction). For the GCM with the lowest change, the range is reductions of 5% to 34% (median is a 25% reduction). For the GCM with the highest change, the range is increases of 5% to 49% (median is an 18% increase).
Figure 4 shows that for the GCM with the median change, the change in the average annual evapotranspiration is a 2% increase in each case. For the GCM with the lowest change, the range is increases of nil to 2% (median is a 1% increase). For the GCM with the highest change, the range is increases of 3% to 4% (median is a 3% increase).
Secure Yield
The results of the pilot study with respect to secure yield are shown in Table 2. Columns (2), (3) and (4) show the secure yield for each of the 11 utilities in the pilot study for the historical data, the median of 15 GCMs and the lowest GCM on the basis of the ‘5/10/10 rule’.
Columns (6) and (7) show the changes in secure yield for the median of 15 GCMs and the lowest GCM in percentage terms. For the median GCM (column (6)) the change in secure yield varies from an increase of 3% (Utility 2) to a reduction of 25% (Utility 9). For the lowest GCM (column (7)) the change in secure yield varies from a 6% reduction (Utility 2) to a reduction of 54% (Utility 9). S. Samra, P. Cloke
As discussed in Samra & Cloke (2010 :5) the Steering Group considers that a balanced approach to determining the secure yield after climate change would be to adopt the lesser of: a) secure yield for the median of 15 GCMs on the basis of the ‘5/10/10 rule’ b) secure yield for the GCM with the lowest secure yield on the basis of a ‘5/10/25 rule’; the 25% severity of restrictions under this rule amounts to being able to ‘survive’ occurrence of the lowest GCM, albeit with relatively harsh water restrictions to cope with the reduced availability of water.
Thus a utility’s core planning under a) above would be on the basis of the ‘5/10/10 rule’. However, under b) above, the utility would also need to ensure its system would be able to survive the lowest GCM under the severe restrictions involved in a ‘5/10/25 rule’.
Column (5) of Table 2 shows the secure yield of the lowest GCM on the basis of 25% severity of restrictions 11 -9% (ie. a ‘5/10/25 rule’). For comparison purposes, the -12% -9% percentage change in secure yield is shown in +3% column (8). -2%
The above approach is considered to provide a -26% reasonable balance between avoiding excessive capital expenditure by the utilities and avoiding very harsh -6% future drought water restrictions. The 25% severity for -50% -6% the GCM with the lowest secure yield is considered to be acceptable in view of the low probability of occurrence of -27% such a GCM and is informed by the outcomes of at least -8% 35% reduction in consumption achieved by several NSW Figure 5: Map of NSW showing adopted % change utilities in the current drought, including Goulburn, in Year 2030 Secure Yield due to climate change Orange and the Central Coast (Samra & Cloke, 2010: for each utility in the pilot study 5). Note: The adopted change in the Year 2030 secure yield due For Utility 9, the changes in secure yield for the existing small to climate change for each utility is shown in column (9) storage dam and for the proposed enlargement of the dam of Table 2 and Figure 5. This is identical with the values were -50% and -29% respectively. shown in column (6), for 4 utilities (2, 3, 4 and 11). The adopted changes for the other 7 utilities are on the basis of 25% severity of restrictions for the lowest GCM, and are up to 25 percentage points lower than for the median GCM.
The 3 utilities with a reduction in the adopted secure yield of over 25% are inland utilities in mid and southern NSW. This finding is consistent with the Victorian expectation of increasing drought severities.
Storage behaviour diagrams for each utility are shown in Figures A1 to A12 in Appendix A on page 11. These show the storage behaviour (expressed as % of full storage capacity) while delivering an annual demand77equivalent to the secure yield determined for the historical data for a repeat of: • the historical climate conditions and • for a repeat of the climate changed conditions that produced the o highest, o median and o lowest climate changed secure yield for each utility.
Using the climate changed inflows, Figures A1 to A12 show that except for Utility 10 (Figure A11), the storages did not empty while supplying a demand equivalent to the historic secure yield for each utility. This includes the results in Figures A9 and A10 for Utility 9 which had the largest reduction in secure yield. It is important to note that the existing small storage capacity for Utility 9 results in a 50% reduction in secure yield (column 9 of Table 2). However after the proposed augmentation of the storage dam, there would be only a 29% reduction in the secure yield, which demonstrates that the impact of climate change is system dependent.
7 Unrestricted demand was supplied until the storage volume fell to the restriction volume for each utility (typically about 50% to 60% of full capacity). Thereafter 90% of the demand was supplied until there was a significant recovery in the storage volume, when the unrestricted demand was resumed. As it was necessary to use the first year of each dataset to initialise the daily rainfall-runoff models, each simulation was generally carried out with the remaining 111 years of daily hydroclimate data. S. Samra, P. Cloke
30% 5% 20% 0% 10% -5% 0% -10% -10% -20% -15% -30% -20%
% Change in Secure Yield Secure in Change % -40% % Change in Secure Yield Secure in Change % -25% -50% -30% -60% 1 2 3 4 5 6 7 8 9 10 11 1 2 3 4 5 6 7 8 91011
Utility Utility Median of 15 GCMs Lowest GCM yield Highest GCM yield Figure 6: Median % Change in the Secure Yield from the 15 Global Climate Models compared with Figure 7: % Change in the Secure Yield for the the result for the Historical Data Set Global Climate Models (GCMs) shown compared with the result for the Historical Data Set
Figure 6 provides a graphical representation of the percentage change in secure yield for the GCM with the median secure yield, in comparison with the historical data set. These results are as shown in column (6) of Table 2 and range from an increase of 3% to a reduction of 25%.
Figure 7 also provides a graphical representation of this percentage change for the GCM with the lowest secure yield (from column (7) of Table 2) and that for the GCM with the highest secure yield, in comparison with the historical data set. As also noted above, the results for the GCM with the lowest secure yield range from a reduction of 6% to a reduction of 54% (column (7) of Table 2). The results for the GCM with the highest secure yield range from an increase of 22% to a reduction of 2%.
The GCMs which provided the median, lowest and highest changes in the average annual rainfall, streamflow and evapotranspiration8 (refer to Figures 2 to 4) are not necessarily those which resulted in the median, lowest and highest changes in secure yield (refer to Figure 7).
A report on the pilot study will be published on the NSW Office of Water website in 2010 in order to disseminate the results and findings of the study.
Tables 3 and 4 show the key characteristics of the 4 simulations shown for each utility in Figures A1 to A12 on page 12, Table 3 provides a comparison of the resulting minimum storage volume for each simulation and indicates that the minimum storage volume for the historical data set ranges from 31% to 49% of the full storage capacity (column (3)). For the median of GCMs, the minimum storage volume ranges from 23% to 49%, with 3 utilities having a minimum storage volume of 23% to 25% of capacity (column (4)). However, for the lowest GCM, 4 utilities have a minimum storage of under 15% of capacity (Utilities 7, 9, 10 and 11), with the storage volume for the small Utility 10 emptying for a period of 6 months (column (5)). For the highest GCM, the minimum storage volume ranges from 32% to 51% of capacity (column (6)).
Table 3: Comparison of Minimum Storage Volumes
Storage Minimum Storage Volume (%) while supplying the Historical Secure Yield Water Capacity Historical Data Set Median of 15 Global Lowest GCM Highest GCM Utility (ML) Climate Models (GCMs)
(1) (2) (3) (4) (5) (6) 1 35,600 39 30 20 40 2 5,500 31 33 27 41 3 4,500 43 49 31 51 4 4,900 46 44 42 46 5 3,780 49 34 24 37 6 460 34 31 22 42 7 22,500 37 23 10 43 8 15,500 38 38 23 46 9 850 37 25 9 37 9+ 2,470 37 30 14 42 10 100 31 29 0 for 6 months 32 11 14,800 33 23 14 39 + Enlarged storage
8 Eg. for Utility 1, the median rainfall, streamflow, evapotranspiration and secure yield resulted from GCMs 5, 5 , 9 and 14 respectively. S. Samra, P. Cloke Table 4: Comparison of Storage Drawdowns
% of the time storage is drawn down below volumes shown while supplying the Historical Secure Yield Water Historical Data Set Median of 15 Global Climate Lowest GCM Highest GCM Utility Models (GCMs)
(1) (2) (3) (4) (5) 60% 40% 20% 60% 40% 20% 60% 40% 20% 60% 40% 20% 1 1.4 0.1 0.0 1.5 0.5 0.0 3.1 0.7 0.1 1.2 0.0 0.0 2 3.7 0.8 0.0 2.8 0.7 0.0 5.0 0.8 0.0 1.1 0.0 0.0 3 0.7 0.0 0.0 0.8 0.0 0.0 1.3 0.1 0.0 0.5 0.0 0.0 4 1.5 0.0 0.0 2.1 0.0 0.0 2.9 0.0 0.0 1.6 0.0 0.0 5 0.2 0.0 0.0 1.1 0.2 0.0 2.1 0.3 0.0 0.7 0.0 0.0 6 1.4 0.2 0.0 1.1 0.2 0.0 2.3 0.4 0.0 0.7 0.0 0.0 7 5.0 0.4 0.0 9.5 1.4 0.0 18 5.2 0.8 2.5 0.0 0.0 8 7.0 0.2 0.0 6.1 0.3 0.0 16 2.9 0.0 1.0 0.0 0.0 9 1.4 0.2 0.0 1.7 0.6 0.0 2.5 0.8 0.2 0.8 0.1 0.0 9+ 1.4 0.2 0.0 1.5 0.4 0.0 2.4 0.5 0.1 1.0 0.0 0.0 10 2.0 0.5 0.0 2.7 0.8 0.0 4.3 1.4 0.7 1.5 0.4 0.0 11 1.5 0.3 0.0 3.4 0.7 0.0 4.9 1.3 0.4 1.6 0.1 0.0 + Enlarged storage
In summary, Table 3 shows that for the median GCM, the minimum resulting storage volume for most of the utilities is a little lower than that for the historical data, indicating slightly more severe droughts than had been experienced historically. For the lowest GCM, all the minimum storage volumes are much lower than the historical data set. This indicates the occurrence of much more severe droughts, with 5 of the utilities experiencing a minimum storage volume of under 15% of full capacity, in comparison with the historical data set, where the minimum storage volume was 31% of full capacity.
For the 4 simulations for each utility discussed in Table 3 above, Table 4 provides a comparison of the percentage of time each storage is drawn down below 60%, 40% and 20% of full capacity. These draw downs indicate the relative vulnerability of each water supply to supply failure due to emptying of the storage. For the historical data set (column (2)) of Table 4 shows that the percentage of time the storage volume falls below 60% of full capacity exceeds 5% only for Utility 8, where restrictions are implemented at a storage capacity of 55% under the ‘5/10/10 rule’. Column (3) of Table 4 shows that for the median of GCMs, 2 utilities (Utilities 7 & 8) have storage volumes under 60% of capacity for more than 5% of the time. Only these 2 utilities have such storage volumes for more than 5% of the time for the lowest GCM, but the duration now extends to 16% to 18% of the time for this GCM (column (4)). For the highest GCM, the duration of such storage volumes does not exceed 2.5% of the time for any utility (column (5)).
Table 4 also shows that for the historical data set (column (2)), the percentage of time the storage volume falls below 40% of full capacity, which could be expected in a severe drought, does not exceed 0.8% for all the utilities. Column (3) of Table 4 shows that for the median of GCMs, only Utility 7 has such storage volumes exceeding 0.8% of the time. However, for the lowest GCM only 7 utilities have such storage volumes not exceeding 0.8% of the time, with the other 4 utilities (Utilities 7, 8, 10 and 11)) experiencing durations of 1.3% to 5.2% of the time (column (4)). For the highest GCM, the duration of such storage volumes does not exceed 0.4% of the time (column (5)).
In addition, Table 4 shows that for the historical data set (column (2)), the median of GCMs (column (3)) and the highest GCM (column (5)), the storage volume never falls below 20% of full capacity, which could be expected to occur only in an extreme drought. However, for the lowest GCM, 5 utilities (Utilities 1, 7, 9, 10 and 11) have a storage volume below 20% of capacity for at least 0.1% of the time (column (4)).
As previously noted, the Best-Practice Management Guidelines require each NSW water utility to prepare a comprehensive 30-year IWCM Strategy. The IWCM strategies will need to include assessment of the secure yield of the utility’s water supply on the basis of new NSW guidelines proposed for release in late 2010. The utilities will be able to soundly plan for the security of their water supply for climate change by developing and implementing their 30-year IWCM strategy on the basis of the climate changed secure yield determined along the lines of the pilot study for 11 NSW water supplies.
As noted on page 3, the pilot study has focused on climate change projections for the Year 2030 based on predictions for the A1B mid range warming emissions scenario. This is not only due to the availability of the daily database but because there is only a small difference in the climate change projections between different emissions scenarios for the year 2030. These differences will be magnified for longer-term projections, such as year for the year 2050 or 2070.
S. Samra, P. Cloke DISCUSSION The 1895-1902 Federation Drought The severe 2001-2007 drought has been claimed as the worst drought since records began in Australia and has resulted in questioning of the reliability of several major water supplies in Australia. Fortunately NSW country town water supplies that had been planned on the basis of the NSW security of supply basis (ie. 5/10/20 rule) have been able to maintain the expected supply. It is hypothesised that this is because the 5/10/20 rule incorporates the very severe Federation drought of 1895-1902 and allows for maintaining a 20% restricted supply through in effect a ‘1 in 1000 year’ drought (Cloke & Samra, 2009 :13).
It is understood consideration of Perth’s and Melbourne’s water supply reliability was until recently based on flow records post the Federation drought, as shown in their plots of inflows (from 1911 for Perth and from 1913 for Melbourne) (Gill, 2008 and Rhodes et al, 2010). The plot of inflows to Perth’s water supply headworks has been repeatedly shown as an example of a shifting climate.
Figure 8: Annual Historic Flows Periodic Comparison
An equivalent plot of inflows for a Tablelands water utility in central NSW [catchment area 100 km2] is shown in Figure 8. With the inclusion of the Federation drought it suggests that the 2001-2007 drought was more likely to be due to climate variability rather than climate change and in terms of water supply headworks was not the worst drought on record.
If the Federation drought and pre 1915 droughts had not been incorporated in the water supply planning, secure yields for many NSW water supplies would have been determined to have been much higher and may have then been impacted by the 2001-2007 drought. For example for Utility 7, post the Federation drought, the secure yield would have been determined as some 25% higher and post 1915, some 50% higher than the historical secure yield. This highlights the importance of including the Federation Drought in any security of supply simulation studies to avoid such over-estimation of secure yield.
Accordingly, it is considered that the robustness of the NSW security of supply basis, combined with analysis for climate change as developed in the pilot study, will continue to provide reliable and cost-effective water supply security for NSW country towns.
Reducing uncertainty in climate models The overall summary of the Ozwater ’10 Workshop on Climate Change Impacts on the Water Sector (Claydon, et al., 2010: 3) includes:
‘Reducing uncertainty in climate models is an active area of research – in particular coupled ocean-atmosphere general circulation models (GCMs). There have already been (published) steps made to provide this more refined (downscaled) output in Bureau of Meteorology and CSIRO climate projections, especially for drought. However, the core aspects of how best to apply these various models using sophisticated integrated modelling procedures remains an ongoing interesting research and operational issue.’ It is acknowledged that reducing uncertainty in climate models and how best to apply them is an area of ongoing research. S. Samra, P. Cloke However, water supply planning and decision making requires assessment of the impact of climate change on water supply security. At present, the best available downscaled daily hydrometeorological data in Australia is for 15 GCMs along the lines developed by the Murray Darling Basin Sustainable Yields Project. Such data is now available for all of NSW and Victoria, as well as for all of the Murray Darling Basin, including Adelaide. It is therefore considered that the analysis carried out in this pilot study could be used to assess the Year 2030 climate change impacts for urban water utilities in the areas with such downscaled data which have surface water supplies with storage dams.
In addition, there are some major research activities such as the research in SEACI910Theme 2 which focus on improving hydroclimate change projections for south-eastern Australia. They are specifically investigating (i) GCM assessment and selection for hydrological application and (ii) assessing the relative merits of different downscaling methods and relative uncertainties in various components in estimating climate change impact on runoff (GCM projections, downscaling methods and hydrological modelling) (Vaze J., 2010).
The above research includes consideration of dynamic downscaling, which has the potential to improve the projections of drought persistence for severe droughts.
Accordingly, as such better hydroclimate change data becomes available in the future, it should be applied in future planning. In this regard, where a utility has sufficient supply capacity to enable it to defer a major capital investment decision for additional surface water supplies for 5 or more years, it should do so, as the better hydroclimate change data likely to be available by that time would enable the utility to make a more robust investment decision.
CONCLUSIONS
1 A sound basis has been developed for non-metropolitan urban water utilities to assess the impact of climate change for the Year 2030 on the secure yield of their urban water supply. This is an adaptive management approach which enables utilities to carry out sound climate change planning and decision making immediately, using the existing 112 years of downscaled daily hydrometeorological data sets for 15 GCMs. As better hydroclimate change projections become available in the future, these will need to be applied in future planning by the utilities.
2 The results for the 11 utilities in the pilot study are shown in Figure 5 on page 6. These indicate that the main impacts on Year 2030 secure yield are: • no greater than a reduction of 9% for the 7 coastal and tablelands utilities • reductions of almost 30% for the 3 inland utilities in mid and southern NSW, after allowing for the proposed augmentation of the existing small storage capacity for Utility 9.
3 Future utility 30-year IWCM strategies in NSW will need to include assessment of the secure yield of the utility’s water supply in accordance with the analysis reported for the pilot study. Implementation of these strategies, together with the required 6-yearly updates, will address the future water security of these utilities.
ACKNOWLEDGMENTS Each member of the Climate Change Steering Group for their valuable strategic advice and inputs. Peter Ledwos, Ian Burton and Richard Cooke of the NSW Office of Water for their significant contributions to the pilot study. Chee Chen and Dr Liz Chen of NSW Public Works Hydrology Group who carried out the detailed modelling required to produce the results provided in the pilot study. The many NSW Councils which have engaged NSW Public Works over the years to carry out yield studies, thus enabling use of the study models for the analysis reported in the pilot study.
REFERENCES Chiew, F.S., Vaze, J., Viney, N.R., Perraud, J-M., Teng, J., Jordan,P.W., Kirono,D. and Young, W.J., 2008. Estimation of Impact of Climate Change and Development on Runoff Across the Murray-Darling Basin in Lambert, M., Daniell, T. and Leonard, M., (Eds) Proceedings of Water Down Under 2008, Adelaide, 14-17 April, pp.1957-1968. Chiew FHS, Teng J,Kirno D, Frost AJ, Bathols JM, Vaze J, Viney NR, Young WJ, Hennessy KJ and Cai WJ, 2008 Climate data for hydrologic scenario modelling across the Murray-Darling Basin. A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project. CSIRO, Australia.
9 SEACI – South-East Australian Climate Initiative
S. Samra, P. Cloke Claydon, G., McDonald, N., Doolan, J., Harten, G., Galligan, D. and Stone, R., 2010. Workshop Outcomes – Climate Change Impacts on the Water Sector, OzWater ’10, Brisbane, March 2010.
Cloke, P.S., 1995. Sizing of Water Supply Headworks on a Security of Supply Basis, in Samra, S. and Cloke, P., (Eds) Preprints of Drought Planning and Forecasting Seminar, Sydney, 20 July 1995, Institution of Engineers, Australia. Cloke, P.S., 2008. Water Supply Security: Do the 5/10/20 Secure Yield Rules Fail the 2001-2007 Drought and Climate Change? Water Management Conference, Local Government and Shires Associations, Ballina 2008. Cloke, P.S., Samra, S., 2009. Impacts of the 2001-2007 Drought and Climate Change on Security of Water supplies in Country NSW, H2009 Hydrology and Water Resources Symposium, Newcastle 2009. Department of Water and Energy, 2007. Best-Practice Management of Water Supply and Sewerage Guidelines. Gill, J., 2008.Sustainable Water Management in A Drying Climate, Lambert, in M., Daniell, T. and Leonard, M., (Eds) Proceedings of Water Down Under 2008, Adelaide, 14-17 April, pp. 26-27. NSW Office of Water 2010 (1). 2008-09 NSW Water Supply and Sewerage Performance Monitoring Report. NSW Office of Water 2010 (2). 2008-09 NSW Water Supply and Sewerage Benchmarking Report. NSW Public Works, 1986. Water Supply Investigation Manual. Rhodes, B.G., Tsioulos, C., Tan, K.,, Baxter,K., and Elsum,G., 2010. Climate Change Adaption - Learnings from a changed Climate, Ozwater’10, Brisbane, March 2010. Samra, S. & Cloke, P.S. 2010. NSW Strategy for Addressing Impact of Climate Change on Non-Metropolitan Water Supplies, Ozwater’10, Brisbane, March 2010. Samra, S. and French, R., 1988. Risk and Reliability for NSW Country Town Water Supply Headworks, Preprints of National Workshop on Planning and Management of Water Resource Systems, Adelaide, 23-25 November 1988. Vaze, J. Teng J., Post D.,Chiew F.,Perraud J-M. and Kirono D. 2008. Future climate and runoff projections (~2030) for New South Wales and Australian Capital Territory, NSW Department of Water and Energy, Sydney Vaze, J., 2010. Personal communication.
APPENDIX A
100% 100%
75% 75%
50% 50%
25% 25%
0% 0% 1895 1920 1945 1970 1995 1896 1921 1946 1971 1996 YEAR YEAR M edian Lo west H ighest H isto rical M edian Lo west H ighest H isto rical
Figure A1: Storage Behaviour Diagram for repeat of years Figure A2: Storage Behaviour Diagram for repeat of years 1895 to 2006 for different climate conditions for Utility 1 1896 to 2006 for different climate conditions for Utility 2
100% 100%
75% 75%
50% 50%
25% 25%
0% 0% 1896 1921 1946 1971 1996 YEAR 1895 1920 1945 1970 1995 YEAR M edian Lo west H ighest H isto rical M edian Lo west H ighest H isto rical
Figure A3: Storage Behaviour Diagram for repeat of years Figure A4: Storage Behaviour Diagram for repeat of years 1896 to 2006 for different climate conditions for Utility 3 1895 to 2006 for different climate conditions for Utility 4 APPENDIX A S. Samra, P. Cloke
100% 100%
75% 75%
50% 50%
25% 25%
0% 0% 1896 1921 1946 1971 1996 1896 1921 1946 1971 1996 YEAR YEAR M edian Lo west H ighest H isto rical M edian Lo west H ighest H isto rical
Figure A5: Storage Behaviour Diagram for repeat of years Figure A6: Storage Behaviour Diagram for repeat of years 1896 to 2006 for different climate conditions for Utility 5 1896 to 2006 for different climate conditions for Utility 6
100% 100%
75% 75%
50% 50%
25% 25%
0% 0% 1896 1921 1946 1971 1996 1896 1921 1946 1971 1996 YEAR YEAR M edian Lo west H ighest H isto rical M edian Lo west H ighest H isto rical
Figure A7: Storage Behaviour Diagram for repeat of years Figure A8: Storage Behaviour Diagram for repeat of years 1896 to 2006 for different climate conditions for Utility 7 1896 to 2006 for different climate conditions for Utility 8
100% 100%
75% 75%
50% 50%
25% 25%
0% 0% 1898 1923 1948 1973 1998 1898 1923 1948 1973 1998 YEAR YEAR M edian Lo west H ighest H isto rical M edian Lo west H ighest H isto rical Figure A9: Storage Behaviour Diagram for repeat of years Figure A10: Storage Behaviour Diagram for repeat of years 1898 to 2006 for different climate conditions for Utility 9 – 1898 to 2006 for different climate conditions for Utility 9 – Existing Storage Enlarged Storage
100% 100%
75% 75%
50% 50%
25% 25%
0% 0% 1896 1921 1946 1971 1996 1895 1920 1945 1970 1995 YEAR YEAR M edian Lo west H ighest H isto rical M edian Lo west H ighest H isto rical
Figure A11: Storage Behaviour Diagram for repeat of years Figure A12: Storage Behaviour Diagram for repeat of years 1896 to 2006 for different climate conditions for Utility 10 1895 to 2003 for different climate conditions for Utility 11
Appendix D QBL RESULTS
Assessment of Environmental, Social and Governance Criteria Performance Score (2)
D1 SW4 SW5 E2 Longer Restriction Burrendong Mulyan Creek SH2 RW1 IPR Membrane R1 Criterion Score (1) Weighting Periods Pipeline Dam BSC Stg 3 Rainwater Tanks Plant Lake Rowlands Environmental Group Infrastructure footprint 5 0.19 10 5 2 5 8 8 1 Protection of water quality and flow values 5 0.19 10 9 1 3 9 8 1 Efficient use of water resource 5 0.19 10 8 3 6 9 8 5 Enhancement of habitat values 4 0.15 5 3 1 3 5 5.5 2 Carbon footprint/GHG 3 0.11 10.0 1.0 8.1 8.0 10.0 1.4 3.8 Resilience to climate change 5 0.19 10 8 2 9 8 10 3 Total weighted environmental 1 9.26 6.11 2.53 5.59 8.15 7.26 2.57 Social Group Security and reliability of urban water service 5 0.28 1.0 10.0 1.4 3.0 1.0 9.7 3.0 Aesthetics of water supply 3 0.17 10 9 8 9 9 7 9 Protect public health 5 0.28 10 9 8 8 6 7 8 Change in TRB (typical residential bill) 5 0.28 10.0 2.1 6.8 8.6 6.2 1.0 2.8 Total weighted social 1 7.50 7.35 5.83 6.96 5.16 6.09 5.32 Governance Group Management and control of water assets 3 0.22 10 8 10 8 7 9 5 Level of service 3 0.22 1.0 10.0 1.4 3.0 1.0 9.7 3.0 Complexity of delivering scheme 3 0.22 9 5 1 5 8 3 3 Capacity building 4.5 0.33 10 5 5 7 9.9 8 5 Total weighted governance 1 7.78 6.78 4.42 5.90 6.86 7.49 4.10 Environmental, social and governance score (ESGS) 24.54 20.24 12.78 18.45 20.16 20.84 11.99
(1) score as 1 to 5 where 5 applies to a critical indicator and 1 applies to the least important indicator (can have equal scores and more than one 5 etc) (2) assign a relative peformance score (1 to 10) for each criteria: 1 = worst; 10 = best.
Quadruple Bottom Line Assessment
D1 SW4 SW5 E2 Longer Restriction Burrendong Mulyan Creek SH2 RW1 IPR Membrane R1 Criterion Periods Pipeline Dam BSC Stg 3 Rainwater Tanks Plant Lake Rowlands Capital cost ($M) 0.00 102.99 43.16 11.49 51.50 57.86 84.50 NPV Capital Cost ($M) 0.00 76.52 33.92 12.20 42.23 54.94 73.92 NPV Operation and Maintenance Cost ($M) 0.00 11.22 1.36 3.10 0.00 45.60 5.64 Total NPV ($M) 0.00 87.74 35.28 15.30 42.23 100.54 79.56 Environmental, social and governance score (ESGS) 24.54 20.24 12.78 18.45 20.16 20.84 11.99 ESGS ranking 1 3 6 5 4 2 7
ESGS/$M 24537.02 0.23 0.36 1.21 0.48 0.21 0.15 Overall QBL Ranking 1 5 4 2 3 6 7
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