POWER AND WATER CORPORATION

DARWIN REGION WATER SUPPLY STRATEGY 2013 Darwin Region Water Supply Strategy

#1080991/04-2015

power and water corporation Darwin Region Water Supply Strategy i

Contents

1 EXECUTIVE SUMMARY...... 1 3.7 Emergency Supply...... 18

1.1 Introduction...... 1 3.8 Water Demand Trends...... 19

1.2 Water Supply Security and Sustainability...... 1 3.9 Water Supply Pricing...... 20

1.2.1 Risk – Sustainability of Supply...... 1 4 WATER DEMAND FORECASTING...... 21 1.2.2 Mitigation – Sustainability of Supply...... 1 4.1 Introduction...... 21 1.2.3 Risk – Security of Supply...... 1 4.2 Methodology...... 22 1.2.4 Mitigation – Security of Supply...... 2 4.3 Bulk Water Demand Projections...... 22 1.3 Immediate Supply Risks – by 2015...... 2

1.3.1 Risk...... 2 4.4 Adopted Growth Rates...... 22

1.3.2 Mitigation...... 2 4.4.1 Base Case...... 22 4.4.2 Modelled Loads...... 23 1.4 Short Term Supply Risks – by 2020...... 2 4.4.3 Alternative Demand Growth Scenarios...... 23 1.4.1 Risk...... 2

1.4.2 Mitigation...... 2 4.5 Future Improvements to Demand Modelling...... 23

1.5 Medium Term Supply Risks – Beyond 2020...... 2 5 FUTURE WATER CHALLENGES...... 24 1.5.1 Risk...... 2 5.1 Climate Change...... 24 1.5.2 Mitigation...... 2 5.2 Greenhouse Gas Emissions...... 25 1.6 Planning Uncertainties...... 3 6 DEMAND REDUCTION STRATEGIES...... 26 1.6.1 Risk...... 3

1.6.2 Mitigation...... 3 6.1 Urban Water Use...... 26 6.1.1 End Water Use...... 27 1.7 Catchment Risks...... 3 6.1.2 Benchmarking...... 28 1.7.1 Risk...... 3

1.7.2 Mitigation...... 3 6.2 Community Attitudes to Water Use...... 28 6.2.1 Key findings...... 28 1.8 Summary of Key Activities...... 4 6.2.2 Power and Water’s Response to the Survey...... 29 GLOSSARY OF TERMS...... 6 6.3 Drivers for Demand Management...... 29 2 INTRODUCTION...... 7 6.4 Demand and Supply Management Initiatives...... 29 2.1 Background Information...... 7 6.4.1 Darwin Water Smart...... 30

2.2 Key Objectives...... 7 6.4.2 Non-revenue Water...... 32

2.3 Previous Long-term Planning...... 7 6.4.3 Water Tariff Pricing Signals...... 32

2.4 Strategy Development...... 7 6.4.4 Sustaining Water Demand Savings...... 32

2.5 Regulatory Environment...... 7 7 FUTURE WATER SOURCE OPTIONS...... 33

3 CURRENT WATER SYSTEM REVIEW...... 9 7.1 History...... 33

3.1 Water Sources...... 9 7.2 Immediate Action to Address

3.1.1 Darwin River Dam...... 10 Emergency Supply Shortfall...... 33

3.1.2 Manton Dam...... 10 7.3 Source Augmentation in the Short Term...... 34

3.1.3 McMinns and Howard East Borefields...... 10 7.3.1 Further Development of . the Howard East Borefield...... 34 3.2 Water treatment...... 12 7.3.2 Manton Dam Return to Service...... 34 3.2.1 Water Quality...... 12 7.4 Strauss Water Storage and Treatment Facility...... 34 3.3 Distribution Network...... 12 7.5 Source Augmentation Options for 3.4 Recent Water Supply Trends...... 14 the Medium Term...... 36 3.4.1 Meteorological Influences – El Niño . 7.5.1 Future Dam Sites...... 36 and La Niña...... 14 7.5.2 Augmentation of Manton Dam’s Storage...... 40 3.4.2 Rainfall...... 14 7.5.3 Adelaide River Off-stream . 3.4.3 Demand...... 15 Water Storage Scheme...... 41 3.4.4 Water Storage...... 16 7.5.4 Desalination...... 42 3.4.5 Water Conservation...... 16 7.6 Alternative Supply Options...... 42 3.5 Level of Service Objectives...... 17 7.6.1 Water Sensitive Urban Design...... 42 3.6 System Yield...... 18 7.6.2 Rainwater Tanks...... 42 3.6.1 Headroom Requirement...... 18 7.6.3 Greywater Reuse...... 42 3.6.2 Target System Yield...... 18 7.6.4 Stormwater Reuse...... 43

7.6.5 Recycled Wastewater...... 43

power and water corporation ii Darwin Region Water Supply Strategy

7.7 Evaporation Reduction Technology...... 43 Figure 16: Factors Influencing Water Demand...... 21 7.8 Excluded Options...... 44 Figure 17: Darwin Region – Projected Bulk . 7.8.1 Darwin River Dam Storage Augmentation...... 44 Water Demand...... 22 7.8.2 Darwin River Dam – Further Extraction Figure 18: Demand Projection Based on . Supported by Water Treatment...... 44 ‘High Growth’ Scenario...... 23 7.8.3 Lambell’s Borefield...... 44 7.8.4 Continued Development of the . Figure 19: Darwin Region Water Supply ...... Howard East Borefield...... 44 Consumption Segmentation 26

7.8.5 Alternative Dam Sites...... 44 Figure 20: Darwin Average Water End Use...... 26 7.8.6 Existing Dams and Lakes...... 46 Figure 21: Darwin Seasonal Water End Use...... 27 7.8.7 Hanna’s Pool on the Finniss River...... 46 Figure 22: Average Annual Residential . 8 DEVELOPMENT OF PLANS...... 47 Water Supplied (kL/ property)...... 28 8.1 Demand/Supply Model...... 47 Figure 23: Existing and Planned Emergency . 8.2 Demand Driven Water Source Supply Capability...... 33 Development Programme...... 47 Figure 24: Site Map for Strauss Water . 8.3 Capital Expenditure Programme...... 49 Treatment Facility...... 35

9 MANAGEMENT OF RISK AND UNCERTAINTY...... 50 Figure 25: Plan of Future Dam Site Options . 9.1 Water Demand Growth...... 50 for the Darwin Region...... 37

9.2 Impacts of Climate Change...... 50 Figure 26: Proposed Upper Adelaide River Dam Site . 9.3 Impact of Government Policy...... 50 and Affected Land Parcels...... 38

9.4 Catchment Risks...... 50 Figure 27: Manton Dam – Potential Storage ...... 10 STAKEHOLDER CONSULTATION...... 51 Augmentation 40 Figure 28: Adelaide River Off-stream Water . 11 REFERENCES...... 52 Storage Scheme...... 41 APPENDIX 1: LAND TENURE AND LAND ZONING MAPS FOR DARWIN REGION WATER SUPPLY CATCHMENTS...... 53 Figure 29: Previously Considered Dam Sites...... 45 LIST OF FIGURES Figure 30: Current Water Source . Development Programme...... 48 Figure 1: Application of Level of Service Objectives to Darwin River Dam...... 1 Figure 31: Alternative Programme – For Planning . and Design Purposes...... 48 Figure 2: Current Water Source Development Programme...... 4 Figure 3: Alternative Programme – For . LIST OF TABLES Planning and Design Purposes...... 5 Table 1: Summary of Source Availability...... 2

Figure 4: Locality Plan of the Darwin Region...... 8 Table 2: Summary of Key Activities – Darwin . Region Water Supply Strategy...... 5 Figure 5: Water Sources for the Darwin . Region Water Supply System...... 9 Table 3: Darwin Region Water Strategy Key Objectives...... 7 Figure 6: Overview of the Darwin Region Water . Table 4: Howard East and McMinns Borefield . Supply Distribution System...... 13 Production Bore Details and Extraction Limits...... 11

Figure 7: Darwin Region Long Term Rainfall Trend...... 14 Table 5: Summary of Source Availability...... 12

Figure 8: Darwin River Dam Catchment Rainfall...... 14 Table 6: Annual Water Demand Variability...... 15

Figure 9: Residential Water Use...... 15 Table 7: Summary of Reliability of Supply . and System Yield...... 19 Figure 10: Darwin River Dam Storage . Levels - 1978 – 2013...... 16 Table 8: Base Case Population Growth to 2030...... 22 Figure 11: Application of Level of Service Objectives . Table 9: Major Industrial Development . to Darwin River Dam...... 18 in the Darwin Region...... 23 Figure 12: Darwin Region Water Consumption . Table 10: Climate Change Predictions for . by Customer Type...... 19 the Darwin Region...... 24

Figure 13: Darwin Region Water Consumption . Table 11: Previous Water Efficiency Initiatives...... 30 Trend by Customer Type...... 19 Table 12: Darwin Water Smart Initiatives...... 31 Figure 14: Darwin Region Water Demand – . Table 13: Capital Investment Programme – Water . Seasonal Impacts...... 20 Source Development Projects...... 49 Figure 15: Residential Water Tariff Comparison...... 20

power and water corporation Darwin Region Water Supply Strategy 1

1 Executive summary

1.1 Introduction 1.2.1 Risk – Sustainability of Supply Using Power and Water’s water resource modelling, the yields of the The Darwin Region Water Supply A sustained series of poor wet seasons existing water sources have been Strategy – hereafter called the could mean insufficient recharge to calculated for each of the level-of Strategy – details the Power and Water Darwin River Dam, causing water levels service objectives. In this way, the Corporation’s plan to balance demand to fall steadily in the region’s principal total system yield is determined, in for water with the capability of supply water supply source. This would place turn informing the programmed to a planning horizon of 2030. The the continuity of supply at risk. development of water sources. Strategy covers the capacity and make- up of the current water supply system, 1.2.2 Mitigation – Sustainability The target system yield incorporates forecast growth in demand, existing of Supply 10 per cent headroom between annual and proposed initiatives for demand demand for water and capability of To ensure appropriate water security, management, future water source supply. The headroom provision buffers planning and management objectives options, and a programme for the large annual fluctuations in observed that define a level of service for the development of new water sources. (historical) demand (+/- 10 per cent), Darwin region water supply have which are being driven by variable The Darwin region water supply been developed. The level-of-service annual rainfall and wet season periods system currently sources water from objectives provide for two levels of in the Darwin region. The headroom the Darwin River Dam (85 per cent) reliability of water supply: 95 per cent also caters for any significant and and the McMinns and Howard East unrestricted demand reliability (water unplanned step increases in demand Borefields (15 per cent). Water is not restrictions 1 in 20 years), and 99 per arising from potential rapid industrial currently sourced from Manton Dam cent restricted demand reliability development in the region. owing to infrastructure constraints, (severe water restrictions 1 in 100 water quality challenges and recreation years). The Strategy incorporates Figure 1 (below) illustrates the on the reservoir. a drought-response plan, which application of the level of service manages periods of low inflows . objectives to Darwin River Dam. 1.2 Water Supply Security and to the system, and an emergency- Sustainability response plan, to deal with . 1.2.3 Risk – Security of Supply prolonged severe drought. Darwin region water supply is strongly In the event of an unexpected loss influenced by climate, including the The level-of-service objectives include a of supply from the region’s principal seasonal nature of rainfall in the wet/ four-stage regime of water restrictions. water resource, Darwin River Dam, dry tropics, the variability of rainfall The regime provides Power and Water water supply to the Darwin region from year to year (which affects annual with a way to manage demand during would be greatly affected. Loss of water demand and inflows to Darwin periods of low inflows to the region’s supply could be caused by, for . River Dam), and the forecast impacts reservoirs owing to drought, or in the example, contamination, . of climate change, particularly a likely event of a delay in the programmed equipment failure or terrorism. increase in evapotranspiration. development of new water sources.

Figure 1: Application of Level of Service Objectives to Darwin River Dam

Relative Frequency of level Volume Description Demand Reliability trigger (m AHD) (GL) (%) (%) (%) (1 in X years) Working Volume 45.86 320 100 FSL 100 39 100 31 Stage 1 90 95 20 Stage 1 (1 in 20 years) 37 65 20 Stage 2 80 not defined not defined Drought Stage 2 35.5 44.5 14 Stage 3 65 not defined not defined Response Stage 3 Reserve 34 28 9 Stage 4 50 99 100 Stage 4 Contingency (1 in 100 years) 32 15 5 Dead Storage Provides 2 years supply Storage at stage 4 restrictions Dead Storage 28 0 0 Empty FSL = Full Supply Level

power and water corporation 2 Darwin Region Water Supply Strategy

1.2.4 Mitigation – Security of Supply Table 1 (below) shows how Darwin 1.4.2 Mitigation region water supply’s existing sources In the event that supply from Darwin To support continued growth in the of water contribute to the current total River Dam becomes unavailable, Power region while deferring the need for system yield. and Water aims to provide an alternate significant capital investment in supply from a source independent The current target system yield, new water sources, Power and Water of Darwin River Dam. Such a source which incorporates the 10 per cent has developed an accelerated and would supply the region over the headroom requirement, is 47,864 ML/ expanded demand management short term and during the emergency. yr, representing an immediate shortfall programme called ‘Living Water Smart’. Groundwater from the McMinns of 5,084 ML/yr. Living Water Smart aims to reduce and Howard East Borefields could be water demand by 10,000 ML/yr by used to diversify sources of supply 1.3.2 Mitigation 2018. The programme will do this in this way. Furthermore, and in the Planned further development of the by improving asset management absence of an alternative supply that is Howard East Borefield in 2014/15 (reducing water losses and managing independent of Darwin River Dam, the is designed to address the lack of system pressure) and through a groundwater supply at the borefields redundancy, enabling the borefield to comprehensive programme of . must have adequate redundancy. This provide sufficient emergency supply water conservation. means the borefields should meet an capacity for a 2030 planning horizon. ‘n-2’ reliability criterion, whereby the Achieving Living Water Smart’s savings The connection of Manton Dam, groundwater supply would continue targets will defer the need to connect planned for 2025 will further augment to meet the supply diversity objective new sources of water in the Darwin the emergency supply at that time. even in the event that the two . region by up to seven years (to 2025). highest-yielding bores fail. Enhancing the redundancy of the The next step in Power and Water’s Howard East Borefield will also allow water source development programme 1.3 Immediate Supply Risks Power and Water to reliably access is the return to service of Manton Dam, – by 2015 its existing licensed groundwater which will provide additional supply allocation. This will increase the of 7,400 ML/yr to the Darwin region. 1.3.1 Risk total amount of water available for Reconnecting Manton Dam to the extraction from connected sources The existing groundwater supply system will also significantly enhance to 45,200 ML/yr, again reducing the fails to meet the requirement for the emergency supply capacity. shortfall in the water supply system. borefield redundancy. Consequently Planning and design for the return to the supply fails to meet Power and 1.4 Short Term Supply Risks service of Manton Dam is continuing, Water’s supply diversity objective – by 2020 and can be fast-tracked should Living for the current demand. Further, the Water Smart’s water demand savings lack of redundancy means Power and 1.4.1 Risk targets not be achieved. Additionally, Water is unable to make full use of the Power and Water could introduce . groundwater allocation for which it . Population-driven growth in demand, low-level water restrictions to achieve is licensed. as well as incremental increases the targeted reduction in demand. associated with large industrial The water supply system’s yield is developments in the Darwin region, equal to the combined yields from 1.5 Medium Term Supply is driving the planning for additional connected water sources, taking into Risks – Beyond 2020 sources of water in the short term. account infrastructure and licensing constraints. The current water supply 1.5.1 Risk system yield is 42,780 ML/yr, compared Further organic demand growth and with a total system demand in continued industrial expansion will 2012/13 of 42,805 ML. require the development of additional Table 1: sources of water in the medium Summary of Source Availability term. Climate change is forecast Available extraction to impact on supply by increasing Licenced extraction [limited by infrastructure or yield] evapotranspiration, which will lead Source (ML/yr) (ML/yr) to reduced inflows to reservoirs and decreasing yields. McMinns and Howard East Borefields 8,420 6,000 1.5.2 Mitigation Darwin River Dam 49,100 36,780 Power and Water’s demand Manton Dam 7,300 0 management strategy provides for TOTAL 64,820 42,780 further water conservation initiatives beyond 2020. Beyond the return to service of Manton Dam, planning and investigations

power and water corporation Darwin Region Water Supply Strategy 3

are underway for an additional major Power and Water’s water demand/ 1.7.2 Mitigation source of water for the Darwin region supply model is ‘reset’ every year Power and Water has developed water supply. Options currently being after the end of the financial year, a Catchments and Water Source considered include: so that demand is forecast from the Protection Strategy to support the most recent demand data. Demand • An in-stream dam (on the upper . proactive management and protection modelling and forecasting are being Adelaide River); of its water supply catchments. improved through interrogation of • An off-stream storage (in the water consumption data by customer Wellhead protection zones have Marrakai region), filled with water type, and by analysing impacts on been established around production harvested from flood flows in the demand from seasonal and annual bores to help reduce the risk of Adelaide River; weather fluctuations. contamination. In areas where rural • Augmentation of Manton . residential development has occurred Five-yearly reviews of yield are Dam’s storage; adjacent to existing bores, Power and undertaken for the sources comprising Water works with the Department of • Desalination; and/or the Darwin region’s water supply. The Health to ensure the installation of • A range of decentralised integrated reviews use updated local and regional site-appropriate wastewater treatment water management solutions, meteorological information and data, and disposal systems. including rainwater tanks, greywater and factor in the latest information reuse and wastewater recycling to on climate change. Climate change There may be an opportunity to reduce the reliance on the potable adaptation strategies for water partially shift Power and Water’s water system for non-potable uses. agencies are being developed at a regular extraction of water from the National level, and Power and Water is McMinn’s Borefield to Howard East 1.6 Planning Uncertainties monitoring developments in this area. Borefield, further reducing the risk of contamination. The shift could The Northern Territory Government 1.6.1 Risk accompany the planned further manages the sustainable use of the development of the Howard East There are a number of inherent region’s water resources through a Borefileld, which aims to enhance uncertainties associated with water water allocation planning process. redundancy in Power and Water’s supply planning for a 20-year period: Power and Water is a member of a groundwater supply. However, the number of water allocation advisory • Water demand growth is subject McMinn’s Borefield will remain a committees, and also actively consults to a range of influences, including critical component of Power and with the Department of Land Resource population growth, economic Water’s groundwater supply capability. activity and the impact of . Management in its planning for the major projects; development of new water sources. Power and Water regularly reviews its catchment management activities to • Climate change is forecast to have 1.7 Catchment Risks protect source water quality. Some of a significant impact on yields the most important activities include available from the region’s water 1.7.1 Risk managing fire, weeds and . supply sources, including increasing feral animals, and catchment . evapotranspiration and reducing A number of significant catchment- security and surveillance. runoff and recharge, however a great related risks have the potential to deal of uncertainty remains as to impact on the sources of Darwin A water treatment plant will be the rate of change and the level of region’s water supply. developed as part of returning Manton impact; and Dam to service. In time, the water In the McMinns Borefield, land treatment plant could be expanded • Regulation of water extraction/ adjacent to Power and Water’s water to also treat water from Darwin River abstraction is an area of uncertainty, supply bores has been developed . Dam, providing additional measures as contemporary approaches to for rural residential and horticultural to reduce risk where undertaken in water management in the Northern land uses. These land uses pose a . support of Power and Water’s drinking Territory are currently being risk of contamination to the public water management objectives. developed and implemented. water supply. 1.6.2 Mitigation Conditions in the region’s surface water catchments also pose a number Forecasting growth in water demand of significant risks to water quality in requires analysing a number of factors, reservoirs. These risks include illegal including: Historical trends, population access to the catchment, erosion and growth forecasts from the Department flood damage, bush fires, feral animals of Treasury and Finance and the and weeds. Australian Bureau of Statistics, and forecasts of major urban and industry development from the Department . of Business and the Land . Development Corporation.

power and water corporation 4 Darwin Region Water Supply Strategy

1.8 Summary of Key Activities As shown, returning Manton Dam Power and Water recognises the to service significantly augments reductions in water demand Figure 2 (below) represents the the capacity of the water supply targeted under Living Water Smart current water source development system. Before this time however, the are ambitious, and contingent upon programme, and is an output from modelling suggests water restrictions sustained community and Government Power and Water’s demand/supply may be required in some years. On support. As a prudent way to manage modelling. The programme reflects occasion, the demand for water will this risk, Power and Water is continuing key planning assumptions, including approach the capacity of the system to the planning and design work for achieving water demand targets set supply it, and will encroach upon the Manton Dam’s return to service and down under Living Water Smart. 10 per cent headroom requirement. for future sources of water so this programme can be fast-tracked should growth in demand outpace demand management efforts. Figure 2: Current Water Source Development Programme

Industrial Step Demands Demand Projection Based On PWC BASE - 1.45 % Residential Demand Management: -20.60% Total by 2018 Historical Demand Industrial Demand Management: -21.60% Total by 2018 Supply Capacity Climate Change Impact on Demand: +2.66% Total by 2030 10% headroom requirement infringed Climate Change Impact on Supply: -10.00% Total by 2030 Augmentation Dates

100,000

t

e

efield - me n r vi c e r B o t S efield Dam - elo p r o a s t E n B o De v r t d L nton Dam - a s a r in Rive r th e r E w e F S M a Ret u w r 50,000 d H o F u a r Da r Rai s w H o Consumption (ML/annum) 2001/02 2010/11 2014/15 2025/26 0 1999/00 2004/05 2009/10 2014/15 2019/20 2024/25 2029/30 Year

Figure 3 (on the following page) Table 2 (on the following page) formal update and public release every shows an alternative programme, summarises the key activities to be five years. which has been prepared assuming delivered under the Strategy to a 2030 Power and Water will review the initial 50 per cent of the Living Water Smart planning horizon. The activities include results of Living Water Smart in late demand-management targets are providing additional supply capacity 2015. The review will determine when achieved. This represents the earliest to manage demand for water and to Manton Dam should be returned to achievable programme, considering the engage with the community around service and whether low level water significant number of engineering and issues of water supply and demand restrictions are needed to achieve environmental studies and approvals management. It is intended that the water demand savings targets. that are required, and making allowance Strategy be reviewed annually, with a for construction times.

power and water corporation Darwin Region Water Supply Strategy 5

Figure 3: Alternative Programme – For Planning and Design Purposes

Industrial Step Demands Demand Projection Based On PWC BASE - 1.45 % Residential Demand Management: -10.30% Total by 2018 Historical Demand Industrial Demand Management: -10.70% Total by 2018 Supply Capacity Climate Change Impact on Demand: +2.66% Total by 2030 10% headroom requirement infringed Climate Change Impact on Supply: -10.00% Total by 2030 Augmentation Dates

100,000 Next Water Source Manton Dam - Return to Service 50,000 Howard East Borefield - Further Development Darwin River Dam - Raise FSL Howard East Borefield Consumption (ML/annum) 2001/02 2010/11 2014/15 2017/18 2025/26 0 1999/00 2004/05 2009/10 2014/15 2019/20 2024/25 2029/30 Year

Table 2: Summary of Key Activities - Darwin Region Water Supply Strategy Timeframe Key Activities Outcomes By 2015 Implement Living Water Smart Reduce per capita water consumption Embed water conservative community culture

Engage with community around water supply and demand issues Community input to next issue of Darwin Region Water Supply Strategy Further development of the Howard East Borefield Increased emergency supply capability Increased reliability of extracting existing licensed groundwater allocation Undertake environmental and engineering studies on a range of . Identify preferred medium-term water supply medium-term water supply options for the Darwin region option for the Darwin region By 2016 Review initial results of Living Water Smart and refine demand Review timing for return to service of Manton management initiatives Dam and assess the need for water restrictions to achieve water demand savings By 2020 Review and refine demand management strategy Reduce per capita water consumption Sustain water conservative community culture

Publish next issue of the Darwin Region Water Supply Strategy Darwin Region Water Supply Strategy responds to community expectations By 2025 Return Manton Dam to service Increased supply capability Enhanced emergency supply capability Improved diversity of supply Beyond Continue to implement demand management action plan Reduce per capita water consumption 2025 Develop medium term water supply source Increased supply capability Enhanced emergency supply capability Improved diversity of supply

power and water corporation 6 Darwin Region Water Supply Strategy

GLOSSARY OF TERMS

Augmentation Recycled water Works required to increase . Water from sewage or industrial water supply processes that is treated to appropriate standards for its intended use Aquifer An underground layer of water- Level of service objectives bearing rock or materials from which An adopted standard of water . groundwater may be extracted. supply that endeavours to achieve supply outcomes expected by the . Catchment community, by using a range of An area of land where run-off enters a measures including the desirable particular river system or reservoir maximum frequency, duration and Demand management severity of water restrictions Initiatives that endeavour to reduce water consumption and encourage Surface water Water stored or transported above more efficient water use and reduce ground (i.e. in lakes, rivers, dams) water losses from the system System yield Drought Response Plans A figure derived from models that Short term action plans that provide refers to the volume of water that effective responses to deal with the can be harvested from a water supply occurrence of droughts system in order to achieve the adopted Groundwater standard of service All subsurface water, generally occupying pore spaces and . Unrestricted water demand The total volume of water used by fractures in rock and soil consumers during periods without Megalitre (ML) water restrictions 1,000,000 litres Water demand Potable. The average annual water demand Suitable for drinking based on water consumption and population projections

power and water corporation Darwin Region Water Supply Strategy 7

2 Introduction

2.1 Background Information Table 3: Darwin Region Water Strategy Key Objectives The development of the Darwin Region Water Supply Strategy demonstrates Key Objectives: the commitment of Power and Water 1. Providing sustainable and economical long term water resource planning to more efficient urban water use, for the Darwin Region; and to identifying supply options that 2. Establishing a balance between sustainable supply options and demand will maintain an appropriate balance management initiatives; between urban water supply and demand for the next 20 years. 3. Reducing bulk raw water demand, and per capita water consumption; The strategy identifies programmed 4. Maximising the utilisation of existing infrastructure and already . water source development projects for disturbed natural water systems prior to developing new water sources; the Darwin region, as well as exploring 5. Assessing climate change impacts in the development of future supply options for the development of future and demand scenarios; water sources. 6. Identifying new and alternative local water resource options . for consideration; 2.2 Key Objectives 7. Integrating alternative water supply options into future water . The strategy aims to achieve supply planning; sustainable urban water management 8. Ensuring water resource planning is undertaken in a transparent and in the short and long term through a auditable framework; and range of measures focussed on: 9. Engaging local communities in planning for long term sustainability of • Securing water supplies their water resources. • Reducing water demand • Balancing water supply with growth 2.3 Previous Long-term Planning Sewerage, Power and Water in demand Corporation, 2010. Long-term water supply planning is • Supplying water in a financially an ongoing process requiring regular • Survey outcomes, Community responsible manner. review. This document will be reviewed Attitudes to Water Use, Power and and updated every five years. Water Corporation, 2006. • Framework for Urban Water Resource Previous long-term planning reports Planning, Water Services Association that were used to develop this strategy of Australia (WSAA), 2005. include: • Guidelines for the Development of • Darwin Water Story, 2005 a Water Supply Demand Strategy, • Darwin Bulk Water Strategy, 2004 Department of Sustainability and • Water Resources for the Greater Environment (DSE), Victoria, 2005. Darwin Area - Darwin Water • Darwin Water Story, Power and Water Resources Strategy, 1999 Corporation, 2005. • Darwin Rural Area South Further information on references is - Water Supply Development provided in Section 11 REFERENCES. Master Plan, 1996 • Darwin Regional Water Supply and 2.5 Regulatory Environment Land Management Strategy, 1988 Power and Water is a Government Further information on references is Owned Corporation. The multi-utility provided in Section 11 REFERENCES. is responsible for the provision of water supply, sewerage and electricity 2.4 Strategy Development services and a five-member Board steers the organisation. The development and presentation of the Strategy is informed by a number The Northern Territory Treasurer is of documents, including: the Shareholding Minister, and Power • Planning Guidelines for Water and Water reports to the Minister for Supply and Sewerage, Queensland Essential Services (as the portfolio Department of Environment and Minister). A three-member Utilities Resource Management, 2010. Commission acts as regulator for Government. The Northern Territory • Power and Water Corporation Government sets utility tariffs in Supplements for the Planning consultation with Power and Water. Guidelines for Water Supply and

power and water corporation 8 Darwin Region Water Supply Strategy

Water resources in the Northern in accordance with the National Water The water allocation planning Territory are regulated by the Initiative and the NT Water Act. Water process has commenced in the Department of Land Resources and Allocation Plans have been created, or Koolpinyah (Howard East) Aquifer. The Management (DLRM). Extraction from are underway or proposed, in places groundwater resource is considered to surface or groundwater resources for where current or potential water be under stress and extraction may be Public Water Supply requires licensing use could pose a risk to the ongoing exceeding sustainable levels. The Water under the Water Act. Extraction availability and health of the resource. Allocation Planning process is expected licenses are granted by the Controller to limit extraction to sustainable levels The Water Act specifies that extraction of Water Resources, who must take and achieve an equitable share of the licenses are to be issued for a a number of factors into account resource between consumptive users, maximum of 10 years and can be when issuing a licence, including whilst providing for environmental and varied at any time. Upon the Minister’s environmental and cultural needs. The cultural water requirements. advice, a licence can be granted for a Department of Health regulates the longer period and a number of current public health aspects of public drinking Power and Water licenses, including water supplies. those for Darwin, have been granted Water allocations, or entitlements, are for 50 years. However where Water provided through Water Allocation Allocation Plans are in place, the Plans, which are developed by DLRM, licenses have been issued for 10 years.

Figure 4: Locality Plan of the Darwin Region

A R A F U R A S E A

MELVILLE BATHURST ISLAND ISLAND

COX PENINSULA DARWIN

BATCHELOR ADELAIDE RIVER

T I M O R S E A

PINE CREEK Groote Eylandt

KATHERINE

HIGHWAY G U L F MATARANKA ROPER O F C A R P E N T A R I A

HIGHWAY TIMBER CREEK

BORROLOOLA

HWY STUART

TABLELANDS BUNTINE ROAD BUNTINE ELLIOTT

HIGHWAY CALVERT

B A R K L Y

T A B L E L A N D HIGHWAY

BARKLY HIGHWAY

TENNANT power and water corporation CREEK

TANAMI HIGHWAY

D E S E R T T A N A M I ROAD

TI-TREE

SANDOVER HIGHWAY PLENTY PLENTY

ROAD KINTORE ALICE SPRINGS

HIGHWAY

KINGS CANYON

S I M P S O N LASSETER D E S E R T

Mutijulu Darwin Region Water Supply Strategy 9

3 Current water system review

3.1 Water Sources The Darwin region’s water supply to McMinns Storage and Transfer system obtains its water from both Station, where the water is blended Darwin is located in the wet-dry surface water sources (via dams) and and piped to Darwin, Palmerston and tropics of Northern Australia, with groundwater (via bores). The great the outer Darwin area. high average temperatures and high proportion (approximately 85 per year-round evapotranspiration, a Power and Water has developed . cent) of the Darwin region’s water monsoonal wet season lasting four to a Water Source Protection Strategy . is currently sourced from Darwin five months, and a largely rain-free dry to support the proactive management River Dam, with an important season lasting seven to eight months and protection of its water supply supplementary supply extracted on average. catchments. from the McMinns and Howard East Borefields. These two sources are piped

Figure 5: Water Sources for the Darwin Region Water Supply System

DARWIN

PALMERSTON MCMINNS AND HOWARD EAST BOREFIELDS

Darwin River Dam Manton Dam

power and water corporation 10 Darwin Region Water Supply Strategy

3.1.1 Darwin River Dam 3.1.2 Manton Dam The majority of the catchment is freehold land owned by Power and Darwin River Dam was constructed in Manton Dam was constructed in the Water and leased to the Conservation 1972 about 50 km south of Darwin. early 1940s by the Department of Land Corporation. The catchment Darwin River Dam is a 518m-long Defence to provide a reliable source of is contained within the Coomalie earth embankment dam, with an water for Darwin during World War II. area and identified in the Coomalie unregulated 265m wide spillway. Located approximately 50km southeast Planning Concepts and Land Use of Darwin, Manton Dam, with a storage In 2010, Power and Water completed Objectives (2000), on unzoned land. capacity of 14,000 ML, was the city’s an upgrade of the embankment and primary source of water until the Land tenure and land zoning plans . raised the spillway at Darwin River commissioning of Darwin River Dam for Manton Dam are at Appendix 1: Dam to increase the full supply level . in 1972. Since that time Manton Dam Land Tenure And Land Zoning . by 1.3m. The augmentation increased has been maintained as an emergency Maps For Darwin Region Water . the yield of the dam by approximately water supply source for the Darwin Supply Catchments. 20 per cent and resulted in a storage Region water supply system. capacity of 320,000 ML. 3.1.3 McMinns and Power and Water is licensed to extract Power and Water is currently licensed Howard East Borefields 7,300 ML/yr from Manton Dam. The to extract 49,100 ML/yr from Darwin supply from Manton is not currently The McMinns Borefield, 30km East River Dam, however its yield has used as an operational source of water South East of Darwin in Howard recently been assessed as 36,780 ML/ due to infrastructure constraints and Springs, was established in the 1960s yr, after the latest of a series of regular water quality challenges, including on the Koolpinyah dolomite aquifer. five-yearly reviews of yield. Extraction recreational use of the dam. Manton beyond the yield is possible, but this Stage 1 of the Howard East Borefield, Dam’s yield has recently been assessed will reduce the level of service offered, the first of four planned stages, was as able to provide a 7,400 ML/yr net resulting in an increased likelihood of commissioned in 2001 to supplement contribution to the Darwin Region’s water restrictions for the community. the existing supply from the McMinns water supply. This issue is further explored in Section Borefield. 3.6 Level of Service. In an emergency, Power and Water The Howard East and McMinns could deliver up to 10 ML/day from Borefields can theoretically provide up 3.1.1.1 Darwin River Dam Catchment Manton Dam to the McMinns Transfer to 20 per cent of the Darwin region’s Station to supplement the water Darwin River Dam catchment is current demand requirements, but, supply system. However the water operated as a closed catchment, being due to infrastructure constraints quality would not comply with the predominantly undeveloped and with including a lack of redundancy in the Australian Drinking Water Guidelines restricted public access. The catchment borefields, current supply is limited to without treatment. Therefore the use management plan aims to control around 15 per cent of Darwin’s water of Manton Dam as a limited short- environmental threats, including wild supply. Importantly, the Howard East term emergency supply during a crisis fires and weeds, and recognises the and McMinns Borefields are an integral such as a cyclone event or failure of catchment’s environmental values, part of the diversification, security the Darwin River Dam supply system being a refuge for native flora and and emergency supply aspects of the is possible, but undesirable in the fauna, including migratory and local Darwin Region Water Supply Strategy. absence of water treatment facilities. bird species, as well as its role as a Power and Water is currently licenced public water supply source. 3.1.2.1 Manton Dam Catchment to extract 8,420 ML/yr from the six The majority of the land is freehold and production bores in the Howard East Manton Dam catchment was operated owned by Power and Water with most and McMinns Borefields as detailed in as a closed catchment until the late of the balance falling within the Finniss Table 4 (on the following page). 1980s when Government directed it River Land Trust. The Northern portion be opened up for recreational use by of the catchment is zoned Water the community. Today water skiers, Management under the NT Planning anglers, picnickers and day trippers visit Scheme, identified in the Litchfield area the dam on a regular basis and it has zone plan. The Southern portion of become a popular freshwater recreation the catchment is contained within the destination for the local populace. Coomalie area and identified in . the Coomalie Planning Concepts and The recreational use of the dam is Land Use Objectives (2000), . managed by the Parks and Wildlife on unzoned land. Commission, who are also responsible for catchment management. Power Land tenure and land zoning plans . and Water remains responsible for . for Darwin River Dam are at Appendix the maintenance of the water . 1: Land Tenure And Land Zoning . supply infrastructure. Maps For Darwin Region Water . Supply Catchments.

power and water corporation Darwin Region Water Supply Strategy 11

Table 4: Howard East and McMinns Borefield Production Bore Details and Extraction Limits Power and Water Bore Equipped Extraction Annual Extraction Location Reference NTG Bore Number Rate (L/s) License Volume (ML) McMinns M54 RN6310 54 2,150 McMinns M55 RN6231 44* 1,020 McMinns M62 RN7048 64 1,020 McMinns M64 RN7071 51 1,550 Howard East HEP1 RN20496 28* 1,300 Howard East HEP2 RN20497 32 1,380 Total 273 8,420

* Not available at the end of the dry season due to declining water levels The annual licensed extraction limits Of the four operational bores in to develop additional extraction reflect the theoretical maximum McMinns Borefield, one is located capacity within the Howard East bore extraction volumes at the time within the road reserve, two are on borefield to improve the reliability . of granting of the licenses. Seasonal freehold land owned by Power and of extraction within the current . variability in groundwater levels, Water, and one is located on a private license limits. individual bore pump limits and a lack freehold land zoned Rural Living. All Power and Water remains vigilant of redundancy in the borefields means of the four bores are adjacent to Rural to the pressures of development, that the licensed annual extraction Living zoned developments. increased human occupation and volume is not reliably achieved with The existing Howard East Borefield is recreation in the area and risks from the current infrastructure. on Crown Land leased to Power and extractive minerals mining. To address Water. The bores are 1km from the these risks, Power and Water has 3.1.3.1 McMinns and Howard East nearest residential development, on identified wellhead protection zones Catchments land zoned Water Management under around the bores in the McMinns When McMinns Borefield was first the NT Planning Scheme, identified in Borefield to support development established in outer Darwin, its the Darwin Region zone plan. An area control and to protect the integrity location was relatively remote. Since identified for expansion of the Howard of the public water supply system. the 1980s however, the area has been East Borefield to the north of the Power and Water liaises closely extensively developed as a rural living existing borefield is on Vacant Crown with the Department of Mines and area and property owners use private Land, planned for transfer to Power and Energy to manage potential impacts bores to extract water from the same Water following resolution of Native from extractive minerals and energy groundwater resource for household Title issues. exploration and development. and irrigation needs, and in a relatively The open and developed nature of the In 2009, an ultraviolet disinfection unregulated manner. catchment represents a number of system was installed at the bore head Whilst DLRM continues to study and risks for Power and Water including of one of the McMinns bores to provide model the groundwater resources in potential contamination of and an additional barrier to contamination the area, it is estimated that Power unsustainable extraction from the of the public water supply. This bore and Water’s annual extraction from its groundwater source. DLRM is currently has been historically impacted by six production bores represents less developing a Water Allocation Plan contamination linked to nearby than 20 per cent of the total annual for the Koolpinyah aquifer and it is residential septic tank effluent . extraction from the aquifer, with considered unlikely that any further disposal systems. the majority of extraction from the allocation will be available to Power approximately 3000 largely unmetered and Water through that process private horticultural and rural beyond the current license limits. residential bores. However, Power and Water is planning

power and water corporation 12 Darwin Region Water Supply Strategy

Table 5: Summary of Source Availability Available Extraction [limited by Licensed Extraction Cumulative System infrastructure or Cumulative System Source (ML/yr) [licensed] (ML/yr) yield] (ML/yr) [available] (ML/yr) McMinns and Howard East Borefields 8,420 8,420 6,000 6,000 Darwin River Dam 49,100 57,520 36,780 42,780 Manton Dam 7,300 64,820 0 42,780

3.2 Water treatment Water supplied from Darwin River Dam Power and Water applies a multiple Recent changes at Darwin River Dam and the McMinns and Howard East barrier approach to protect drinking have increased the area of the water Borefields is essentially untreated other water supplies. The multiple barrier body when full. It is anticipated that than the addition of fluoride at the approach is universally recognised dirty water episodes will increase Darwin River Dam Pumping Station. as the foundation for ensuring safe over the next few years while these drinking water. A ‘barrier’ such as new areas adjust to more frequent Raw water is disinfected with chlorine disinfection is a measure used to immersion. gas at Darwin River Dam. Groundwater reduce water quality risks. Significantly, from the borefield is blended with Consumer expectations are driving the main source of supply (Darwin the water supplied from Darwin River the need to improve aesthetic water River Dam) has a closed catchment. Dam, then disinfected with chlorine quality and require Power and Water The significance of the protection of gas at the McMinns Storage and to consider options to improve the water sources cannot be overstated. Transfer Station. There are a number aesthetic quality of water delivered to of small sodium hypochlorite booster Complaints about the Darwin region’s the community, through planning for systems at various locations in the water quality generally relate to the future water treatment capability. water supply network. way it looks, an aesthetic issue largely governed by seasonal variation in 3.3 Distribution Network A bore in the McMinns Borefield was reservoir water quality and water previously removed from service due The Darwin Region water supply demand. Darwin River Dam is highly to the repeated detection of pathogen system provides potable water to stratified, which limits the mixing of indicators. However an ultraviolet customers in five water supply zones; different layers of water. Stratification disinfection system was installed at Darwin Rural/Palmerston, Stuart Park, occurs when the sun heats the upper the borehead in 2009 to enable its Casuarina, Karama and Channel Island. layers faster than the heat can disperse return to service. into the lower depths. The difference The system provides potable water in density between the hotter surface to approximately 50,000 properties 3.2.1 Water Quality and the cooler bottom limits mixing (including commercial, industrial . Power and Water is committed to between these layers. and Government) and serves providing safe drinking water by a permanent population of This can lead to layers with significantly adopting and implementing the approximately 118,500 people. different water qualities. Seasonal Framework for Management of weather patterns can cause a mixing of Drinking Water Quality included as these layers affecting aesthetic quality. a key part of the Australian Drinking Water Guidelines. Also, with the first major rains of the wet season, or after heavy rainfall Power and Water publishes an associated with cyclones, dissolved annual Drinking Water Quality Report organic matter in the catchment may detailing its drinking water quality enter Darwin River Dam leading to an and performance and how it applies increase in dirty-looking water making it the 12 elements of the Framework through to our taps. for Management of Drinking Water Quality to ensure the quality of water delivered to its customers.

power and water corporation Darwin Region Water Supply Strategy 13

Figure 6: Overview of the Darwin Region Water Supply Distribution System

Nightcliff 2 Tank Casuarina Rapid Creek Tanks Tank Marrara Tank Karama Tanks Winnellie 3 1 Parap Tank Salonika Tank Tank Stuart Park Montoro Tank Tank West Lane Darwin Tank McMinns and Palmerston 4 Tank Howard East Howard Borefields Springs Tank Palmerston

McMinns Resevoir and Transfer Station

Humpty Doo Tank

5

Jenkins Rd Channel Island Booster Station 6

WATER ZONE 1 Stuart Park Zone 2 Casuarina Zone 3 Karama Zone 4 Palmerston Zone 5 Jenkins Road Zone 6 Noonamah Zone

Legend Existing Elevated Tank Existing Ground Level Tank

Darwin River Dam Manton Dam

power and water corporation 14 Darwin Region Water Supply Strategy

3.4 Recent Water Supply Trends meteorological history and resulted . of long term climate change and in above average rainfall in the . it is important to understand the 3.4.1 Meteorological Influences Darwin region, including a record combined effects of potential future – El Niño and La Niña 2918.4mm of rain at the Darwin rainfall, temperature and evaporation airport rain gauge in 2010/11. variations when assessing the Darwin The term El Niño refers to the situation region’s future water supply and when sea surface temperatures in 3.4.2 Rainfall demand balance. the central to eastern Pacific Ocean are significantly warmer than normal. The Darwin region has been enjoying Annual rainfall in the Darwin River This recurs every three to eight years an increasingly wet period of weather, Dam catchment, like that of the and generally results in below average with increasing average rainfall. This Darwin region, is highly variable as rainfall in the Darwin region. When the is illustrated on the long term rainfall illustrated in Figure 8: Darwin River eastern Pacific Ocean is much cooler graph below. This is in stark contrast Dam Catchment Rainfall (right). A than normal, a La Niña event occurs, to Southern Australia where sustained sustained period of below-average generally resulting in above average drought conditions had (until recently) annual rainfall, such as occurred rainfall in the Darwin region. been indicative of a long term decrease between 1986 and 1993 can be in rainfall. considered as drought conditions for The 2010/11 and 2011/12 . the wet/dry tropics, where even in the La Niña events were two of the most This does not mean that the Darwin poorest of wet seasons annual rainfall significant in Australia’s recorded region is immune from the effects reliably exceeds 1,000 mm. Figure 7: Darwin Region Long Term Rainfall Trend

3500 800.00

3000

500.00 2500

2000 200.00

1500

Rainfall (mm) -100.00

1000 Varaince from Median (mm) -400.00 500

y = 3.3199x + 1487.2 -700.00 1901/02 1904/05 1907/08 1910/11 1913/14 1916/17 1919/20 1922/23 1925/26 1928/29 1931/32 1934/35 1937/38 1940/41 1943/44 1946/47 1949/50 1952/53 1955/56 1958/59 1961/62 1964/65 1967/68 1970/71 1973/74 1976/77 1979/80 1982/83 1985/86 1988/89 1991/92 1994/95 1997/98 2000/01 2003/04 2006/07 2009/10 2012/13 Note: Seasons with missing data not shown

Figure 8: Darwin River Dam Catchment Rainfall

3000

Median Rainfall (1582 mm)

2500

2000

1500 Rainfall (mm)

1000

500

0 1969/70 19 73/74 19 74/75 19 75/76 19 76/77 19 77/78 19 78/79 19 80/81 19 81/82 19 82/83 19 83/84 19 84/85 19 85/86 19 87/88 19 88/89 19 89/90 19 90/91 19 91/92 19 92/93 19 92/93 19 93/94 19 94/95 19 95/96 19 96/97 19 97/98 19 98/99 1999/00 20 02/03 20 03/04 20 04/05 20 05/06 20 06/07 20 07/08 20 08/09 20 09/10 20 10/11 20 11/12 2012/13

power and water corporation Darwin Region Water Supply Strategy 15

3.4.3 Demand Figure 9: Residential Water Use Figure 9 (right) shows the significantly high level of residential water use 600 in both Darwin and Alice Springs compared with the national median, 500 which has decreased over the past several years. Of concern is the 400 progressive increase in residential water demand reported for Northern 300 Territory centres. kL/Property Annual water demand is highly 200 weather dependant in the Darwin region. An extended wet season results 100 in a lower annual water demand, . but an extended dry season will . - lead to significantly increased .

annual water demand. 2000/01 2001/02 2002/03 2003/04 2004/05 2005/06 2006/07 2007/08 2008/09 2009/10 2010/11 2011/12 2012/13 Growth in annual water demand has Financial Year Darwin Water Alice Water Australian Municipal Average averaged approximately 2.3 per cent Linear (Darwin Water) Linear (Alice Water) Australian Regional Average in the 30 years since 1980. Annual fluctuations in demand (principally due to the Darwin region’s variable annual rainfall and wet season periods) are a Table 6: regular occurrence and can exceed 10 Annual Water Demand Variability per cent per annum. Demand growth Year Annual Change from Total rainfall Correlation figures for the past thirteen years are demand previous year (mm) between tabulated below. (ML) (%) demand change and rainfall* 2000/01 38,214 6 1,392 1 2001/02 36,872 -4 1,306 - 1 2002/03 39,467 7 1,645 1 2003/04 38,464 -3 2,026 1 2004/05 41,264 7 1,333 1 2005/06 38,276 -7 1,927 1 2006/07 40,531 6 1,652 1 2007/08 39,621 -2 1,908 1 2008/09 43,138 9 1,589 1 2009/10 41,367 -4 2,116 1 2010/11 38,760 -7 2,960 1 2011/12 41,856 8 1,927 - 1 2012/13 42,805 2 1453 1

* 1 = demand increase AND below median rain OR demand decrease AND above median rainfall. Long term median rainfall = 1,716 mm (1941-2012)

power and water corporation 16 Darwin Region Water Supply Strategy

3.4.4 Water Storage annual extraction increases, the end on its customers, there is growing of dry season water level continues momentum to promote water In the Darwin region, both to drop each year. Should a period of conservation measures. It is recognised surface water and groundwater poor wet seasons return, water levels that these efforts need to be resources experience significant in Darwin River Dam could fall to levels substantially ramped up to achieve the fall in level owing to extraction and not previously experienced. objectives of the Strategy. evapotranspiration during each year, but are usually significantly Figure 10 details varying water levels in Power and Water has developed a replenished by rainfall and runoff Darwin River Dam over time. The chart key initiative called ‘Living Water during each wet season. identifies the original full supply level Smart’, which aims to reduce water (FSL) and the new FSL associated with demand by 10,000 ML/yr by 2018 Notably, the Darwin region augmentation of the storage in 2010. through improved asset management experienced a significant series of The Stage 1 water restriction level (reducing water losses and managing poor wet seasons (equivalent to a trigger (further discussed in Section 3.6 system pressure) and a comprehensive drought) of 12 years, from 1984 to Level of Service Objectives) is identified water conservation programme. 1996, in which Darwin River Dam did at 39m AHD. Living Water Smart’s range of demand not fill and spill. Conversely, with above management initiatives are discussed average rainfall during the past fifteen 3.4.5 Water Conservation further in Section 6 - Demand years, Darwin River Dam has filled and Reduction Strategies. spilt most years since 1997, with the Whilst Power and Water has not exception of 2003, 2005 and 2013. As previously imposed water restrictions

Figure 10: Darwin River Dam Storage Levels - 1978 – 2013

47

46

45

44

43

42 Level (m AHD)

41

40

39

38 1978/79 1979/80 1980/81 1981/82 1982/83 1983/84 1984/85 1985/86 1986/87 1987/88 1988/89 1989/90 1990/91 1991/92 1992/93 1993/94 1994/95 1995/96 1996/97 1997/98 1998/99 1999/00 2000/01 2001/02 2002/03 2003/04 2004/05 2005/06 2006/07 2007/08 2008/09 2009/10 2010/11 2011/12 2012/13 2013/14

Date DRD Historic Level OLD Full Supply Level (44.56m) NEW Full Supply Level (45.86m) Stage 1 (39m)

power and water corporation Darwin Region Water Supply Strategy 17

3.5 Level of Service Objectives • An unrestricted demand reliability system will never fail to meet (highly of 95 per cent - water restrictions restricted) demand. The primary objective of a water utility imposed not more than 1 in 20 years is to ensure that the community Emergency water supply source on average; has a safe and reliable water supply options may include (for example): • A drought response plan that system and to communicate this to its • additional groundwater supply, consumers.1 This does not mean there includes a four-stage water restrictions regime, delivering an under an emergency supply licence will never be restrictions, but it does issued by the regulatory authority; mean that the community can expect incremental demand-dampening to never run out of water. effect (to peak demand during the • emergency extraction of river water dry season) of 12.5, 25, 45 and . piped to Darwin River Dam (or This primary objective consists of three 65 per cent (or 10, 20, 35 and . Manton Dam, once it’s connected) main components, namely: 50 per cent when applied across . through a temporary pipeline; 1. The supply system has the capacity a 12-month period); • an emergency desalination plant; or to maintain an adequate level of • A reliability of avoiding stage 4 • a combination of the above, or other supply over most periods in the . (extreme) water restrictions of 99 options not yet identified. long-term. per cent - stage 4 water restrictions, Power and Water is currently assessing 2 contingency storage (and emergency 2. When drought periods occur, a a range of options for emergency supply options) triggered not more drought response plan provides supply and the recommended option than 1 in 100 years; short-term protection against or options will be progressed to design running out of water through • A contingency storage provision, stage, to allow for connection within the implementation of water sized to provide two years of highly a two-year timeframe, should the restrictions. restricted (stage 4) demand to allow contingency storage level be reached. 3. In cases of extreme drought, a time for emergency water supply contingency or emergency plan sources to be connected to the water The following schematic and exists that ensures that basic water supply system; and associated table illustrates the application of the targeted level of needs for a community can be met • A number of emergency water service objectives for the existing for the duration of the emergency. supply options sized to provide Darwin region water supply system. sufficient yield to deliver a highly These high level objectives can be Figure 11 identifies the proportion . restricted (stage 4) demand should translated into specific objectives for a of Darwin River Dam’s storage to extreme drought conditions persist. water supply system, known as ‘level of be used as ‘working volume’ and service’ objectives. The level of service The size of the contingency storage is the proportion that falls within objectives can relate to a number based on maintaining supply under the drought response reserve and of specific measures including the highly restricted (stage 4) demand contingency storage triggers. desirable maximum frequency, duration conditions, where inflows to Darwin and severity of water restrictions River Dam are equal to the lowest two expected by the community. consecutive years inflow in 100 years. In 2012, Power and Water undertook The emergency water supply source a review of levels of service across options are sized to maintain a highly Australia and developed a set of level restricted (stage 4) demand, during a of service objectives for the Darwin period of sustained low inflows (the Region water supply to be used for lowest two consecutive years inflow planning purposes. The target level of in 100 years, repeated in perpetuity) service objectives include: to Darwin River Dam. This provides assurance to the community that the

1 Framework for Urban Water Resource Planning, WSAA, 2005 2 A series of poor wet seasons is defined as a ‘drought’ for the Darwin region.

power and water corporation 18 Darwin Region Water Supply Strategy

Figure 11: Application of Level of Service Objectives to Darwin River Dam

Relative Frequency of level Volume Description Demand Reliability trigger (m AHD) (GL) (%) (%) (%) (1 in X years) Working Volume 45.86 320 100 FSL 100 39 100 31 Stage 1 90 95 20 Stage 1 (1 in 20 years) 37 65 20 Stage 2 80 not not Drought Stage 2 defined defined Response Stage 3 35.5 44.5 14 Stage 3 65 not not Reserve Stage 4 defined defined Contingency (1 in 100 years) Storage 34 28 9 Stage 4 50 99 100 Provides 2 years supply at stage 4 restrictions Dead 32 15 5 Dead Storage Storage 28 0 0 Empty FSL = Full Supply Level

3.6 System Yield 3.6.1 Headroom Requirement 3.7 Emergency Supply ‘System yield’ is a term used to Power and Water aims to maintain In the event that supply from Darwin describe the volume of water that a 10 per cent buffer (headroom) River Dam becomes unavailable, can be harvested in order to achieve between demand and supply capability due to a contamination event or the adopted standard of service. to buffer the regular large annual infrastructure failure, Power and System yield is always associated with fluctuations in demand (+/- 10%) Water aims to provide an alternative a standard of service and reduces driven by the Darwin region’s variable supply, approximately equivalent to as the standard of service increases. annual rainfall and wet season periods, 25 per cent of wet season demand. In practical terms, this means that which strongly influences demand for The supply must be from a source a water supply system may be water. This phenomenon distinguishes independent of Darwin River Dam so acceptable to one community, which the Darwin region from others, and as to maintain short-term emergency is willing to accept more frequent hence no industry standard exists supply capability. Groundwater at the restrictions, and unacceptable to for the provision of headroom. The McMinns and Howard East Borefields another community less tolerant . headroom provision also caters for would be required to meet this supply of restrictions. potential significant unplanned . diversity objective. Furthermore, in step increases in demand associated the absence of an alternative supply Using the Darwin River Dam yield of with rapid industrial development . independent from Darwin River Dam, 36,780 ML/yr, derived by taking into in the region. the groundwater supply must also account the targeted level of service meet an ‘n-2’ reliability criterion. This objectives for the Darwin region water 3.6.2 Target System Yield criterion dictates that should the supply, and the current limitation on two highest-yielding bores fail, the borefield extraction of 6,000 ML/yr, the Due to the large annual fluctuations groundwater supply would continue to current system yield is 42,780 ML/yr in demand, exponential regression meet the supply diversity objective. (refer to Table 4). 3 of historical normalised demand is used to estimate system headroom The existing groundwater supply requirements. Providing for 10% currently fails to meet the reliability system headroom along with customer criteria, and consequently fails to meet growth and demand management the supply diversity objective. initiatives, the target system yield for the Darwin region water supply system is currently 47,864 ML/yr, indicating an immediate system yield shortfall of 5,084 ML/yr, providing the impetus for short-term source augmentation.

3 Includes the increase in yield associated with the 2010 augmentation of Darwin River Dam.

power and water corporation Darwin Region Water Supply Strategy 19

Table 7: Summary of Reliability of Supply and System Yield Item Adopted standard of service • 95% unrestricted demand reliability – water restrictions 1 in 20 years • 99% restricted demand reliability – severe (stage 4) water restrictions 1 in 100 years • 2 year contingency storage – sized to provide time to connect emergency supply sources in extreme drought • Emergency supply sources designed to provide continuity of supply in prolonged, extreme drought Current serviced population 118,523 Current level of unrestricted demand 42,805 ML/yr System yield target (includes 10% headroom) 47,864 ML/yr Current system yield 42,780 ML/yr Current augmentation required to meet adopted standard of service 5,084 ML/yr Current emergency supply capability 7.2 ML/day (target for 2013 is 20.7 ML/yr)

3.8 Water Demand Trends Figure 12: Darwin Region Water Consumption by Customer Type System demand in 2012/13 for the Darwin region was 42,805 ML. Figure 12 (right) depicts the comparative usage of different consumer groups. Consumption by Customer 17 Non-revenue refers to water taken or Type 2012-13 (%) lost from the system that does not Residential generate revenue, such as water lost 3 through meter error, main breaks, Commercial and Industrial Government leakage and theft, and water used for 47 Power and Water flushing of mains and fire fighting. 13 Non-revenue water Community efforts towards water conservation are increasing, but sustained savings in water consumption are yet to be fully realised. Opportunities exist to achieve savings 21 across all consumer groups. This issue is explored further in Section 6 - Demand Reduction Strategies. Figure 13: Darwin Region Water Consumption Trend by Customer Type Figure 13 (right) depicts the recent trends in water consumption for the Power and Water Darwin region across customer types. Non-revenue water Government The Darwin region’s residential per Consumption Trend by Customer Type Commercial and Industrial Residential capita water consumption is one 25000 of the highest in Australia, with no downward trend at this time. Outdoor Residential 20000 water use (irrigation) is a significant contributor to extremely high water demand in the dry season. System 15000 demand peaks during the dry season when demand exceeds 160 ML/day, 10000 reducing to approximately 80 ML/day Consumption (ML) during the wet season. The average residential demand of approximately 5000 460 L/capita/day is up to three times the average per capita demand for Power and Water most Australian utilities. 0 2005-06 2006-07 2007-08 2008-09 2009-10 2010-11 2011-12 2012-13

power and water corporation 20 Darwin Region Water Supply Strategy

Figure 14 (below) demonstrates the seasonal impact of rainfall on water demand in the Darwin region.

Figure 14: Darwin Region Water Demand – Seasonal Impacts 180 50

160 45 Wet Season 40 140 35 120 30 100 25 80 20 Rainfall (mm) Demand (ML/d) 60 15 40 10

20 5

0 0 Jul-12 Jan-13 Jun-13 Apr-13 Oct-12 Nov-12 Aug-12 Mar-13

3.9 Water Supply Pricing The Northern Territory Government Power and Water’s pricing policy (effective 1 January 2013), the water sets water tariffs in consultation with provides for a fixed daily charge tariff increased by a further 30 per Power and Water. The Government dependent on meter size, and a cent along with similar substantial provides Power and Water with volumetric charge based on usage. increases in electricity and sewerage a Community Service Obligation tariffs to improve Power and Water’s Commencing in 2009-10, the water payment to support a uniform financial sustainability. Incorporating tariff was increased by 20 per cent Territory-wide tariff to compensate the 2013 increase, the residential per annum for three consecutive for the variability of cost in providing water tariff of $2.97 per kilolitre is years to start to close the gap water supply services across its slightly below the national average. between operational costs and customer base. tariff-based revenue. In May 2013 Figure 15: Residential Water Tariff Comparison

4.50 $4.24

4.00 $3.51 3.50 $3.06 $2.97 Average: $3.07 3.00 $2.76 $2.66 2.50 $2.27 $/kL 2.00

1.50

1.00

0.50

0.00 SA QLD ACT NT NSW VIC WA

Source: Retailers’ published tariffs, as at 1 May 2013 Notes • The tariff comparisons in the chart are based on average annual consumption of 214kL (WSAA average). Consumption may vary in each jurisdiction from this derived average as a result of water restriction policies. • Tariffs include a variable consumption charge and a fixed daily component.

power and water corporation Darwin Region Water Supply Strategy 21

4 Water demand forecasting

4.1 Introduction moderate demand or to investigate period due to the wide range of factors the provision of alternative and influencing water demand, and has Water demand forecasts are a key additional water supplies. Power therefore used analysis of historical component of developing effective and Water recognises the difficulty trends and developed forecasts using water supply-demand strategies. The in establishing projections that are the most up-to-date local and regional forecasts help determine whether statistically accurate beyond a five-year information. to implement measures that

Figure 16: Factors Influencing Water Demand

Economic Demand Management • Industry type and growth • Community education Future Water Demand • Tourism • Retrofitting and rebates • Water price • Regulation and pricing • Pressure management • Leakage reduction

Demographic Water Use • Population density • Residential Alternative water sources • Housing type • Commercial • New dams or bores • Development and growth • Industrial • Rainwater tanks and greywater • Concessional • Recycled water • Aquifer storage • Desalination Socio-Economic • Behavioural patterns • Cultural factors • Income levels

System Design • Supply source • Infrastructure Climatic • Reticulation design • Temperature • Rainfall • Climate change

Source: Adapted from Guidelines for the Development of a Water Supply-Demand Strategy 2005

power and water corporation 22 Darwin Region Water Supply Strategy

4.2 Methodology Figure 17: Darwin Region – Projected Bulk Water Demand Power and Water forecasts growth in Industrial Step Demands water demand using a combination Residential Demand Management: -20.60% Total by 2018 of population growth forecasts from Industrial Demand Management: -21.60% Total by 2018 Climate Change Impact on Demand: +2.66% Total by 2030 the Australian Bureau of Statistics

(ABS) and the Department of Treasury 100,000 and Finance, as well as forecasts of industrial demand provided by the Department of Business and the Land Development Corporation. The Department of Treasury and Finance’s population forecasts have 50,000 been developed to meet the needs of Northern Territory Government agencies as well as the broader community. The assumptions and parameters on Consumption (ML/annum) which they are based, are the result of extensive consultation within Northern Territory Government. The process 0 has also involved Charles Darwin

University (CDU) whose staff provided 1999/00 2004/05 2009/10 2014/15 2019/20 2024/25 2029/30 expert advice as well as the technical Year

expertise to develop a projections model Demand Projection Based On PWC BASE - 1.45 % (NTPOP). Projection outputs for two Historical Demand scenarios are currently available – the NTG projections scenario and a high 4.4 Adopted Growth Rates Table 8: migration scenario.4 Base Case Population Growth to 2030 Power and Water uses the most up-to- 4.4.1 Base Case date information for the development Power and Water’s base case for Financial Year Population Growth Commencing (Base Case) of water demand projections and plans forecasting growth in demand utilises to carefully review demand forecasts the Department of Treasury and Average to 2030 1.54% each year to help minimise the level Finance’s NTG Projects scenario to 2012 1.70% of uncertainty inherently associated 2025, and the ABS Series B projection 2013 1.70% with long-term forecasts. Annual thereafter. Forecast demands water demand in the Darwin region associated with major industrial 2014 1.70% is strongly influenced by the type development in the Darwin region 2015 1.70% of wet season experienced. Annual have been included in the base 2016 1.60% fluctuations in demand of up to 10 per demand projection as well as climate cent are not uncommon. To dampen change impacts on demand, and 2017 1.60% the impact of annual fluctuations, demand management targets. 2018 1.60% demand forecasts use an exponential regression of historical normalised 2019 1.60% demand as a base. 2020 1.60% 2021 1.40% 4.3 Bulk Water Demand Projections 2022 1.40% 2023 1.40% The base water demand projection shown in the graph (above) indicates 2024 1.40% the expected average annual demand 2025 1.40% in the Darwin region for periods 2026 1.52% without restrictions. The projections are based on average annual 2027 1.50% consumption and do not depict annual 2028 1.47% variations in water consumption . 2029 1.45% that commonly occur due to . climatic variation. 2030 1.43%

4 http://www.nt.gov.au/ntt/economics/nt_population.shtml

power and water corporation Darwin Region Water Supply Strategy 23

Areas of significant demand growth 4.4.3 Alternative Demand 4.5 Future Improvements to forecast for the Darwin region include: Growth Scenarios Demand Modelling • New urban development in A number of other demand forecast The growing focus on water Palmerston East (Bellamack, scenarios are also routinely modelled conservation and the emphasis on Mitchell, Zucolli) and Lee Point to test the sensitivity of the model to identifying new opportunities to (Muirhead); variations in demand. The projection generate water savings are fuelling • Infill development in Darwin CBD below uses the Northern Territory the need to develop better tools for and surrounding suburbs; Treasury’s forecast for ‘high migration’ demand forecasting and analysis. • Potential development in the scenario to 2021, and the ABS Series B Power and Water recognises the Berrimah farm area; projection thereafter, includes climate importance of understanding details change impact on demand and and patterns of water use at the • Potential urban expansion in or assumes no demand management customer’s tap. around Noonamah to the South benefit. The 2030 demand is Over the next five years, Power and West of Palmerston; approximately 57,000 ML/yr, compared Water will work towards improving . • Industrial development in the East to the base case forecast . its ability to model and forecast Arm and Middle Arm areas; of approximately 43,000 ML/yr demand, so as to achieve the . showing how sensitive the model . • A proposed abattoir in the outer following objectives: Darwin area; and is to planning assumptions. • Better understand the factors that • Major industry, such as the proposed influence water demand; Inpex development • Enhance the ability to map water The base case assumes achievement consumption; of Living Water Smart’s targeted water demand savings (reduction in demand • Improve data collection on water use of 10,000 ML/yr by 2018). at the customer’s tap; • Better understand water use by the 4.4.2 Modelled Loads commercial and industry sectors; • Improve ability to measure savings The following forecast demands from water conservation projects; associated with major industrial and development in the Darwin region have been included in demand • Develop more accurate methods modelling. of quantifying water savings from restrictions. Table 9: Major Industrial Development Figure 18: in the Darwin Region Demand Projection Based on ‘High Growth’ Scenario

Year ML/yr Activity Industrial Step Demands Climate Change Impact on Demand: +2.66% Total by 2030 2014 500 Abattoir 100,000 2016 1000 East Arm Port Expansion 2018 1000 Conoco Phillips LNG - 50,000 Stage 2 2025 500 Inpex - Stage 2 Consumption (ML/annum)

0 1999/00 2004/05 2009/10 2014/15 2019/20 2024/25 2029/30 Year

Demand Projection Based On PWC HIGH – 2.13 % Historical Demand

power and water corporation 24 Darwin Region Water Supply Strategy

5 Future water challenge

5.1 Climate Change In the Northern Territory, like A range of climate change outcomes elsewhere, climate change will affect for the Darwin region, obtained from Perhaps the greatest uncertainty meteorological elements including the CSIRO’s 2007 technical report in assessing future water demand temperature, evapotranspiration, – Climate Change in Australia, is against system yield is the potential rainfall (and runoff, and recharge to tabulated below. impact of climate change. groundwater), sea levels and storm Climate change, and particularly global surge and the occurrence and severity warming, has already been evident of cyclones. through recorded meteorological Power and Water has undertaken changes in the Northern Territory and assessments based on a range of elsewhere around the country and different climate change scenarios, and the world. For example, the Territory is a mid-range emissions scenario has already experiencing a rise in average been adopted for modelling to 2030. temperatures5.

Table 10: Climate Change Predictions for the Darwin Region CSIRO Climate Change Predictions Scenario % Change Low Emissions Medium Emissions High Emissions 2030 2050 2070 2030 2050 2070 2030 2050 2070 10th Percentile Rainfall - 3.5 - 7.5 - 7.5 - 7.5 - 7.5 - 15.0 - 7.5 - 15.0 - 15.0 Max Temp 1.4 2.5 3.9 2.5 3.9 3.9 2.5 3.9 5.4 Evaporation ------3.0 3.0 50th Percentile Rainfall ------Max Temp 2.5 3.9 5.4 2.5 5.4 7.0 2.5 5.4 8.6 Evaporation 3.0 6.0 6.0 3.0 6.0 6.0 3.0 6.0 10.0 90th Percentile Rainfall 7.5 7.5 15.0 7.5 15.0 15.0 7.5 15.0 30.0 Max Temp 3.9 5.4 7.0 3.9 7.0 8.6 3.9 8.6 10.9 Evaporation 6.0 6.0 10.0 6.0 10.0 14.0 6.0 14.0 18.0 Red cells indicate the scenarios modelled in the most recent yield assessments

Uncertainties in projected regional The CSIRO report documents a range climate change in 2030 are mostly due of impacts in terms of 50th, 90th to differences between the results of and 10th percentiles. In line with the the various climate models employed Intergovernmental Panel on Climate rather than the different emission Change terminology on percentiles, the scenarios. Projections for 2030 are report indicates a change of less than given for a mid-range emission the 50th percentile has a likelihood scenario. Beyond 2030, the magnitude that is more likely than not, a change of projected climate changes are of less than the 90th percentile is affected more by emissions6 so a high extremely likely, and a change of . emission outcome for 2070 has been less than the 10th percentile is used for assessment of yield impacts extremely unlikely. as a ‘worst case’ scenario.

5 Department of Climate Change, Australian Government (2008) – Fact Sheet – Climate Change – Potential Impacts and Costs – Northern Territory. 6 CSIRO (2007) – Technical report – Climate Change in Australia

power and water corporation Darwin Region Water Supply Strategy 25

The impacts of climate change on The impacts of climate change on In Power and Water’s demand model, yield are expected to be dramatic, demand are more difficult to predict. the effect of climate change on annual with significant increases in Climate change impact assessments total rainfall, average maximum evapotranspiration expected to undertaken by other Australian utility temperature and evaporation, is the significantly affect runoff to storages, organizations and Governments have percentage change relative to the base and higher evaporation from storages, assessed demand impact, including: year realised in the end year. Estimated a particular problem for the . • CSIRO (2003) (for ACTEW) – Climate values for these parameters have Darwin region’s relatively . Change Projections and the Effects been obtained from CSIRO reports. broad, shallow reservoirs. on Water Yield and Water Demand The effects of the changes on climate have then been estimated using linear Modelling of climate change impacts for the ACT – identified potential equations calculated from a linear has identified significant potential climate-related water demand regression analysis of historical data. impact on the yields available from increases of between one and five Manton Dam and Darwin River per cent by 2030 (three per cent 5.2 Greenhouse Gas Emissions Dam. While wet season rainfall is for mid-range climate change not expected to vary significantly, scenarios), and between one and Greenhouse gases are generated increased evapotranspiration in the 16 per cent by 2070 (nine per cent during the delivery of potable water catchment will lead to a reduction for mid-range climate change supplies, with the primary source being in inflows, and this, combined with scenarios). Importantly, the predicted the use of energy to transport and increased evaporation from the dams demand increases doubled if climate treat water. themselves, will lead to a reduction in change is expressed as an increase Power and Water acknowledges available yield. in the frequency of hot periods, as opposed to an increase in mean that producing new water supplies The modelling identified the potential temperatures. will generate greenhouse gases, for a 13 per cent reduction in yield particularly for options where pumping • CSIRO (2005) (for Melbourne Water) from Darwin River Dam and a three per water over long distances or elevations Melbourne Water Climate Change cent reduction in yield from Manton is required. Water sources that require Study identified potential increases Dam by 2030. The modelled impacts water treatment will increase the level in average annual water demand associated with climate change of greenhouse gas generation per due to climate change of between predictions for 2070 show even . unit of water supplied. Desalination 0.5 and 2.3 per cent by 2020, . more impact, although greater for example is an extremely energy and between 1.3 and 6.2 per cent . uncertainty is associated with . intensive water supply source option. longer-term predictions. by 2050. The potential generation of greenhouse gases will be one criterion used in the assessment of future water supply source options.

power and water corporation 26 Darwin Region Water Supply Strategy

6 Demand reduction strategies

Power and Water is undertaking a 6.1 Urban Water Use Figure 19: number of initiatives to reduce the Darwin Region Water Supply Almost 60 per cent of the Darwin amount of water used by consumers Consumption Segmentation region’s water is consumed by the (known as ‘demand management’) . residential sector, a level followed by and water lost from the network the non-residential commercial and 4% system (known as ‘supply Government sectors. Therefore, the 16% management’). Collectively these residential sector has the greatest initiatives are focussed on saving water effect on water consumption in or preserving existing supplies through Darwin – refer Figure 19 (right). a range of voluntary water efficiency measures and involuntary water Further, on average, about three- 24% conservation measures. quarters of the Darwin region’s annual 56% water consumption is for outdoor Demand management water efficiency water use. measures include water-efficient fittings and appliances, technological Water consumption also varies greatly improvements, behavioural with the wet/dry tropical seasons, with Total Consumption (2011-12 FY) change and pricing signals. Supply outdoor use in households increasing 35.540 GL management initiatives include leak up to ten-fold in the dry season. Residential detection, pressure management, Therefore, the Darwin region’s water Commercial Government meter error and theft. consumption and usage patterns . Power and Water are very highly correlated to . In times of need, mandatory water Darwin’s climate. conservation measures such as water Figure 20: restrictions may also be imposed. When compared to the rest of Darwin Average Water End Use Australia, Darwin’s residential water Darwin water consumption from consumption is over twice as much residents and businesses is over 3% as other comparable towns and twice as much as other comparable 13% cities. Additionally, outdoor use is still 25% communities and continues to grow at significantly higher when specifically a higher rate than the population. compared to comparable regions such 6% Previous studies showing how water as Cairns, Townsville and Mackay. 4% 2% is used in homes (water end use 2% studies) reveal outdoor water use is highest. Non-residential irrigation also continues to be high, with large seasonal variances in the Top End. 45%

There are significant benefits in Average 443l/person/day from Smart Metering Trial preserving the Darwin region’s (WSAA Report 2008/2009 493l/person/day) existing water supplies. Therefore Toilets Other (including leaks) Power and Water utilises these water Shower Boat/Car Washing Washing Machine Irrigation end use consumption profiles to Kitchen Pool/Pond implement a range of water-efficiency demand-management strategies, as well as monitor the water network to determine appropriate supply- management initiatives.

power and water corporation Darwin Region Water Supply Strategy 27

6.1.1 Water End Use Figure 21 (right), highlighting the very Figure 21: high influence of climate and garden Darwin Seasonal Water End Use Power and Water conducts water watering and irrigation on the Darwin end use studies and audits from region’s water consumption. time to time in order to analyse how Dry Season consumers use water in homes and Water audits focus on how water businesses. Assessment of these is used in properties, and identify studies determines how efficiently opportunities for consumers to 26% water is being consumed, and informs become more water efficient and 26% Power and Water programs that aim to thereby reduce water use. Power and promote water efficiency. Water regularly undertakes water audits with businesses and promotes Figure 20 (left) shows how Darwin regular self-assessment of water . region households (that have gardens) use. Typically, the water audits reveal . typically use water. While the quantity a financial benefit can be realised. 74% of water consumed between wet and 74% by reducing water use through dry seasons varies greatly due to the irrigation scheduling and design, change in outdoor use, the proportions changing behaviours and upgrading 32% between water uses in the dry do not appliances, without affecting lifestyles change significantly from the annual or core business. IndoorIndoor averages shown. This shows that OutdoorOutdoor almost three-quarters of water used There is capacity therefore, to reduce 68% in Darwin region households with water consumption by encouraging gardens is applied outdoors. water-efficient behaviours, fittings and Indoor appliances in Darwin’s residential and Outdoor However, outdoor water use in houses Wet Season non-residential sectors. with gardens increases markedly from wet to dry seasons as shown in

power and water corporation 28 Darwin Region Water Supply Strategy

6.1.2 Benchmarking Figure 22: Average Annual Residential Water Supplied (kL/property) Other Australian States and Territories categorise water users into groups. It . (National Performance Report 2012-2013) is more convenient to benchmark water use for the purposes of 500 454 comparison, by using residential . 450 and non-residential groups. 400 383

Residential water use is appraised 350 using consumption per household. Non-residential water use is appraised 300 Australian Average: 258 249 213 kL/ property using sector-specific benchmarks; for 250 216 example, water consumption in hotels 200 198 193 may be related to the number of beds 158 151 or rooms used in a year. 150 As residential water use is the largest 100 consumer group, it is best to assess 50

residential water consumption per 0 household and/or per person, as . Darwin Townsville Cairns Perth Mackay Sydney Adelaide SEQ Melbourne this is the best indicator of the . overall water use and efficiency of . a particular community. 6.2 Community Attitudes remain aware of water conservation Figure 22 (right) compares Darwin’s to Water Use behaviour and understand there is residential water use per household room to become more water efficient. In 2005, Power and Water published during the 2012-13 financial year, . It is important however, that all a booklet called The Darwin Water with other comparably-sized cities and sections of the community are involved Story and an accompanying survey other capital cities. in water efficiency actions and that was distributed to explore community they are well informed. As for previous years, the Darwin attitudes around water use in the region’s residential water consumption Darwin region. 6.2.1 Key findings remains more than twice the national A total of 610 surveys were completed average. Moreover, Darwin’s residential The key findings of the surveys by residents (602) and businesses (8) in consumption remains very high, included: even when compared with areas of the greater Darwin area. • More than half of all residents and similar climate, growth pressures and Overall, most residents and businesses businesses believed that water water supply network, such as Cairns, were open to water conservation, and conservation in Darwin is critical. Townsville and Mackay. in favour of measures to reform water • Residents and businesses agreed During the past decade, such growth use. While there was some division in the community about the need for that it is socially responsible for pressures have served to highlight them to monitor water use. how water efficiency measures can permanent water restrictions, other • Being well informed about the effect preserve existing water supplies. measures such as water-efficient of water consumption on the water With community support, these devices in new buildings, using supply system and educated on same communities have successfully recycled water and encouraging the water efficiency actions was a key reduced their annual water use of rainwater tanks (for example driver to saving water. consumption over the past five years. through subsidising schemes) were supported by a majority of residents • Residents and businesses agreed and businesses. that mandatory installation of In 2012, Power and Water conducted water-efficient devices in new focus-group surveys that generally buildings and residences was the confirmed the 2005 survey results. preferred way to encourage water Darwin residents and businesses efficiency (out of five options).

power and water corporation Darwin Region Water Supply Strategy 29

• Suggestions for water management 6.2.2 Power and Water’s Response to expectation that the conservation and social responsibility included the Survey effort should be spread across all ‘organisations to lead by example’ consumer groups. In response to the 2005 and 2012 and ‘educating the public on why survey findings Power and Water: Power and Water seeks to work with water conservation is important all sectors of the community to reduce for Darwin and the Top End whilst • Has put information about . water consumption, and in the area providing specific details about rainwater tanks and grey-water of unaccounted-for water to achieve alternative options (e.g. cost, amount reuse systems on its internet site . the water savings goals. This approach of water saved, details of proposed (www.powerwater.com.au) along better spreads water conservation restrictions)’. with who to contact regarding efforts across the entire consumer base • Those who believed water the use of these measures in the Northern Territory. and prioritises efforts in areas with the conservation was critical were more greatest potential savings. supportive of recycling water and • Encourages residents to review . introducing an environmental levy and benchmark their water end. Power and Water regularly models to support water recycling, and were uses by undertaking an online the benefits of achieving demand more likely to agree that higher interactive virtual water audit at management targets in terms of the water users should pay more. www.powerwater.com.au. deferral of capital expenditure on new water source development. • Among those who did not see water • Has included additional information conservation as a critical issue, the on water bills, which compares water 6.4 Demand and Supply majority believed that the rainfall in use for the billing period with the Management Initiatives the Northern Territory guarantees same period in previous years. our water supply. • Understands the public is sensitive In the short and medium term, • Although the respondents felt to new tariff reform and/or . significant water savings will need to favourable towards water efficient water restrictions. be achieved to moderate the demands devices there was no real support for • Has promoted National Water . of a growing population, and to help introducing step water tariffs and Week events and other initiatives prevent environmental stress during permanent water-saving rules to such as ‘Tapstar saves water’ . an era of greater climate variability encourage water efficiency. a school performance aiming . and resultant impacts on water resources. Power and Water’s customer • Encouraging the purchase of to create awareness about . engagement and other studies have rainwater tanks was the first water conservation. shown there is capacity for consumers preference for most residents • Has developed and promoted a . to become more water efficient and is and businesses. However, when suite of publications providing investigating opportunities for further examining the top two priorities, advice and guidance to householders water demand savings in the future. encouraging greywater systems including the Green Guide and The potential for significant reductions was the most popular overall Water Wise Gardening. across all water consumption groups is initiative. Almost two in three people • Has added to customer bills graphs achievable through the introduction of supported recycling water and that compare the amount of . water efficient technologies, focussed agreed that a levy to support this water, power and greenhouse . incentives to preserve lifestyles, strong would be a good initiative. Eighty . gas emissions used over the . community support and a collective per cent of households and past 12 months, with the average commitment towards water efficiency. businesses agreed they would . residential consumption. use recycled greywater. Power and Water has developed • Provides water audit services to • The majority of residents and experience in demand and supply help businesses analyse water businesses stated they would use management over the past five years consumption and develop water recycled greywater. Encouraging the through various water conservation efficiency management plans. purchase of rainwater tanks was initiatives and industry support. In the first preference for two in five • Continues to survey customers with more recent times, the implementation respondents, followed by effluent a focus on water efficiency attitudes. of Alice Water Smart in 2011 has reuse and greywater systems. provided important contemporary 6.3 Drivers for Demand experience in application of water Management conservation initiatives at a whole- Water efficiency continues to receive of-community level, and within the considerable support from the Northern Territory. Some examples are community and all other levels of outlined in Table 11 (on the following Government. There is also a growing page).

power and water corporation 30 Darwin Region Water Supply Strategy

Table 11: Previous Water Efficiency Initiatives: Initiative Description Leak Management Plan A Leak Management Plan has been implemented in the Darwin region that will systematically monitor, identify and address leakage and pressure management zones in Power and Water’s water supply network. Public Education Campaign Power and Water is implementing various public education campaigns, primarily aimed at improving water efficiency by promotion, publications, billing information, facilitating leadership with key non-residential organizations and schools to support reductions in commercial and residential water consumption. Audits Power and Water sponsors residential audits and undertakes water audits with businesses as part of ongoing consumer engagement to increase awareness and the benefits of water efficiency. Alice Water Smart Power and Water is leading Alice Water Smart, which is a whole of community water efficiency program. Launched in Alice Springs in 2011 and finishing in 2013, Alice Water Smart has been focussing and incentivising residents and businesses to become more water efficient through encouraging voluntary water saving rules, undertaking water audits, offering greater rebates and retrofits, automating irrigation systems in parks and gardens, providing more recycled water and establishing an intensive water loss management and smart metering programs. The consortium partners include the Department of Land Recourse Management, Alice Springs Town Council, Tourism NT and Arid Lands and Environment Centre.

6.4.1 Living Water Smart By working with other Northern • Improve competitiveness of Darwin’s Territory Government agencies and businesses and industry through Power and Water has developed a Councils to implement water efficiency efficient use of water. comprehensive multi-objective and initiatives and provide leadership, multi-faceted water efficiency program • Foster water efficiency compliance the program aims to help Darwin’s called ‘Living Water Smart’. Living in residential and commercial residents and businesses recognise the Water Smart will be implemented over buildings, as measured under the economic and social benefits of being the next five years. The program aims standards of the Building Code of more water efficient. This includes to achieve water savings over the short Australia. Power and Water, which aims to reduce and medium terms, and targets all • Embed water efficient infrastructure water consumption in its own facilities. water consumer groups and users in and practices in Northern Territory the Darwin region’s urban areas. Living Water Smart aims to reduce Government agencies and Darwin annual water consumption in the region Councils. Living Water Smart includes demand Darwin region by 10,000 ML/yr over and supply management initiatives. The initiatives of Living Water Smart five years. The focus of supply management are included in Table 12 (on the initiatives will be managing water Saving water under Living Water Smart following page). loss through leakage reduction and will; better pressure management. Demand • Reduce the amount of water used management initiatives will focus on by Darwin region households working with residents and businesses by an average of 25 per cent by to involve them in deciding the best 2018, compared with 2011-12 ways to change their use of water. consumption levels.

power and water corporation Darwin Region Water Supply Strategy 31

Table 12: Living Water Smart Initiatives Living Water Smart Initiatives Activities Homes & Businesses - Conduct 5000 residential water audits prioritising the highest water users. (Demand Management) - Conduct 250 commercial water audits and produce water efficiency management plans prioritising the highest water users. - Develop water efficiency partnership program for all other businesses. - Develop residential and non-residential (by sector) water efficiency . benchmark guidelines. - Offer incentives for taking up the recommendations from water audits through targeted rebates and smart metering. - Develop permanent voluntary water saving rules for Darwin. Parks Ovals & Road reserves - Install smart water irrigation technology systems to road reserves and 200 parks . (Demand Management) and ovals. - Develop water efficiency management plans and irrigation scheduling tools for parks and ovals. - Encourage early leak detection and response to water leaks and wastage. Accommodation . - Conduct water audits and develop water efficiency plans for 30 key . (Demand Management) accommodation properties. - Develop guidelines for water efficiency benchmarks for the accommodation sector. - Offer incentives for taking up recommendations from water audits through targeted rebates and smart metering. Schools. - Conduct water audits and develop water efficiency plans for 40 schools. (Demand Management) - Develop water efficiency benchmark guidelines. - Offer incentives for taking up recommendations from water audits through targeted rebates and smart metering. - Develop education resources and a delivery program for ongoing water . efficiency education. Hospitals and Defence - Conduct water audits and develop water efficiency plans for hospital . (Demand Management) and Defence facilities. - Develop guidelines for water efficiency benchmarks. - Offer incentives for taking up recommendations from water audits through targeted rebates and smart metering. Reuse and Reticulation - Investigate and plan opportunities to recycle water. (Supply Management) - Develop and implement leak detection program. - Develop and implement pressure management plan. - Provide industry training for leak detection in properties. Smart Metering - Install smart water meters to support the Homes and Businesses, Accommodation, (Enabler) Hospitals and Defence, and Schools projects. - Encourage savings by providing constant awareness of water use . Rebates . - Rebate program customised to support Homes and Businesses, Accommodation, (Enabler) Hospitals and Defence, and Schools projects. - Encourage savings by providing rebates to general public (i.e. not participants in other projects). Administration and Promotion - Encourage savings by general public promotion (i.e. not from participants . (Enabler) in other projects). Tariff increase - Promotion of water efficiency themes in response to recently introduced tariffs to (30%+5%+5%) fully realise price elasticity opportunity. - 0.1% price elasticity.

power and water corporation 32 Darwin Region Water Supply Strategy

6.4.2 Non-revenue Water However, the increased focus on 6.4.4 Sustaining Water water efficiency provided by Living Demand Savings Maintaining the efficiency of the water Water Smart is expected to realise supply system can help to minimise Living Water Smart aims to encourage this demand elasticity from the recent the amount of water unaccounted for, the community to save water by tariff increase of 30 per cent. otherwise called ‘non-revenue water’. promoting water efficient practices To influence consumer behaviour and making available tools to . Non-revenue water includes: and promote water conservation, help residents and businesses . • water loss through mains breaks . the Commonwealth Government’s conserve water. and leakage Productivity Commission has Managing water loss by making it part recommended reducing reliability on • water meter and billing errors of every-day operations, will also help. water restrictions, and emphasising • operational use (flushing etc) the use of water tariff pricing signals Promoting water conservation as a • water theft; and that respond to the scarcity of supply. core business activity for Power and • unmetered fire fighting use. Also, the Commission suggests Water, will help to realise the full Historically, non-revenue water for the introducing a range of tariff structures potential of Living Water Smart, and Darwin region water supply system matched to the customer’s appetite preserve water-efficient behaviour and has been as high as 20 per cent of for risk. infrastructure in the community. total system demand. Unaccounted Power and Water has previously Power and Water will keep abreast of for water represented 19 per cent investigated the introduction of step appropriate technologies to save water, of total system demand in 2012/13. tariffs, whereby a base level of supply as they become available. Power and Water is implementing is provided at a base cost, with an a Leak Management Plan to reduce increased tariff tied to nominated unaccounted for water. This plan has steps in consumption. The introduction informed development of Living Water of step tariffs is not favoured by the

Smart and will be greatly expanded Productivity Commission, but is under supply management initiatives. standard practice for a number of Australian water agencies, where step 6.4.3 Water Tariff Pricing Signals tariffs support water efficiency by The Northern Territory Government rewarding water efficient behaviour. dictates water pricing policy in the Power and Water will continue to . Northern Territory using a flat rate liaise with the Department of tariff policy. Treasury and Finance and the Utilities Power and Water regularly forecasts Commission in order to agree a . retail revenue associated with water water pricing methodology that . consumption. In its modelling of the will provide for a return on Power . impact on demand of increased water and Water’s investment in water pricing, Power and Water assumes a supply infrastructure, and that uses 0.1 per cent reduction in per capita pricing signals to support water demand for every one per cent increase efficiency targets. in price. This assumption is based on interstate studies and is yet to be validated in the Northern Territory.

power and water corporation Darwin Region Water Supply Strategy 33

7 Future water source options

7.1 History Figure 23: Existing and Planned Emergency Supply Capacity Power and Water’s previous strategic plan for supplying water to the Darwin 40 region provided for small incremental increases to supply, matched to 35 relatively low forecasts of growth in 30 demand. The plan covered the short to Emergency Supply Target (2030) medium term (five to 10 years). 25

These small incremental increases 20 to supply were to be provided by Emergency Supply Target (2013) developing three additional stages 15

of the Howard East Borefield over Emergency Supply (ML/d) time. However, improved estimates of 10 sustainable yield from the Koolpinyah 5 aquifer in the Howard East area, have meant that developing the Howard 0 Current Total Current Total Future Total Future Total East Borefield is no longer considered Emergency Supply Emergency Supply Emergency Supply Emergency Supply a sustainable way to supplement the with n-2 Redundancy with n-2 Redundancy Darwin region water supply system. Moreover, because the region is Proposed Additional Extraction Borefield Capacity at Howard East Borefield Existing Extraction Capacity at McMinns and Howard East Borefield growing more rapidly than first forecast – a combined effect of increased population-based * ‘n-2’ refers to a policy requirement to ensure supply capability is maintained should the two highest growth and demand for water from yielding bores in the borefield fail major industrial and commercial developments – Power and Water must develop water sources on a greater scale than was previously planned for this period.

7.2 Immediate Action to Address Emergency Supply Shortfall To address an immediate shortfall in emergency supply capacity, Power and Water is still planning to develop extra extraction capacity at the Howard East Borefield. Further development of the Howard East Borefield will provide additional emergency water supply capacity to a 2030 planning horizon. The connection of Manton Dam, planned for 2025 will further augment the emergency supply capability Figure 23 (right) identifies the existing shortfall and the improvements to emergency supply capacity achieved by further developing the Howard East Borefield. The supply targets represent short-term emergency supply capability approximately equal to 25 per cent of wet season demand.

power and water corporation 34 Darwin Region Water Supply Strategy

7.3 Source Augmentation in the 7.3.2.1 Infrastructure Requirements source represents a significant risk Short Term to the public water supply and is Since the Darwin River Dam was inconsistent with Power and Water’s Limited options exist to significantly commissioned in 1972, Manton Dam’s adherence to the Framework for augment the Darwin region water two transmission mains (300mm Management of Drinking Water Quality, supply in the short term (by 2020). and 375mm) have been used to which is a key component of the Planned augmentation projects aim to pipe water from McMinns transfer Australian Drinking Water Guidelines. maximise the benefit of existing assets station to the rural area (backfeed). and existing sources. However, the pipes are old, with The future of recreational activities at reduced reliability, and can no longer the dam will be carefully reviewed as 7.3.1 Further Development of the be used as transmission mains. A new part of the strategy to return Manton Howard East Borefield transmission main must therefore be Dam to service. Clearly defining constructed to return Manton Dam management responsibilities and As described above, Power and Water to service. The transmission main will liabilities, additional operating controls is planning to further develop the deliver Manton Dam’s water to the and significant operational resources Howard East Borefield in 2014/15 proposed Strauss Water Treatment and will be needed, as well as regular to increase the emergency supply Storage Facility. consultation with recreational user capacity for Darwin in the event of a groups, if recreational use is to continue. short term supply constraint due to Transferring water from Manton Dam to Darwin River Dam for pumping into the infrastructure failure or water quality 7.4 Strauss Water Storage and issues at Darwin River Dam (i.e. not water supply system was assessed as an Treatment Facility related to water resource reliability). option, but discounted on the basis of risk to water quality and supply security. Increased regulation of drinking However, the additional redundancy water quality, rising expectations of in the Howard East Borefield will also The intake tower and suction main consumers and the need for improved allow Power and Water to reliably pipework at Manton Dam have aged risk management has driven the need access its existing total licensed significantly and without significant to plan for the future treatment of groundwater extraction, addressing augmentation, would represent an water for the Darwin region. the majority of the immediate supply unacceptable operational risk were shortfall (2,420 ML/yr of the current they incorporated into the supply Moreover, recent water quality 5,084 ML/yr shortfall). system. Whilst the existing pumping assessments at Manton Dam bring station and pumping equipment forward the need for a major water The further development of the have been maintained to provide treatment facility for the Darwin region Howard East Borefield may also allow for an emergency function, they water supply system. Power and Water to partially shift require replacement to provide the regular groundwater extraction efforts security of operation required for an Power and Water plans to develop the away from the McMinns Borefield operational supply system. A new Strauss Water Treatment and Storage which is located closer to residential intake arrangement, new suction main Facility on approximately 42ha of land land, so as to reduce contamination pipework and a new pumping station adjacent to the intersection of the risk and potential performance will be required to support Manton Stuart Highway and Cox Peninsula impacts on surrounding bores. Dam’s return to service. Road. The site is strategically located at the intersection of the transmission mains from Darwin River Dam and 7.3.2 Manton Dam Return to Service 7.3.2.2 Recreation and Water the planned water transmission main Quality Issues To provide additional water for the from Manton Dam. It provides an ideal Darwin region water supply system In 2008, Power and Water commenced location for major water storage to in the short term, Power and Water a water quality study to determine the service future residential development is planning for the return to service treatment required to improve Manton in the area, and will house new water of Manton Dam. Whilst the current Dam’s water quality to a level suitable storage and water treatment facilities water source development programme for public consumption. to be developed in the short term. identifies Manton Dam’s return to service in 2025, planning and design The water quality studies have identified Water treatment will at first be sized work continues to allow for earlier that the reservoir at Manton Dam to cater for water from Manton Dam connection of Manton Dam should this suffers seasonal thermal stratification only. The planning and design of the be required. (layering), has elevated levels of iron, treatment facility will however, allow manganese, colour and turbidity at for expansion so as to provide whole- Power and Water currently holds a times, and is susceptible to periodic of-system treatment for the Darwin licence to extract water from Manton high levels of cynobacteria (blue-green region water supply in the future. Dam. Water is not presently extracted algae). Significant water treatment will Preliminary design of the treatment from Manton Dam however, owing be necessary to overcome these water process and planning of the site layout to infrastructure constraints and quality challenges. unacceptable water quality. are complete and further planning The Northern Territory Government and investigation is underway. The reconnection of Manton Dam is opened up Manton Dam to recreation Land acquisition has commenced, planned to provide an additional 7,400 in the late 1980s after lobbying from and Power and Water is working ML/yr for the Darwin region water supply. the public and interest groups. Allowing with Government to address the recreation on a potable water supply requirements of the Native Title Act.

power and water corporation Darwin Region Water Supply Strategy 35

Figure 24: Site Map for Strauss Water Treatment Facility

Palmerston Stuart Highway McMinns and Howard East Borefields

Girraween Road

Stuart Highway Proposed Strauss Water Treatment Facility

Cox Peninsula Road

power and water corporation 36 Darwin Region Water Supply Strategy

7.5 Source Augmentation the technologies can be proven at a Options for the commercial scale. Evaporation from Medium Term Darwin River Dam has a major impact on yield. If evaporation from the There are a number of potential reservoir could be reduced, then more sources which could augment the water would be available for extraction. Darwin region’s water supply in . This issue is explored further in 7.7 the medium term (beyond 2020). . Evaporation Reduction Technology. A preliminary assessment of options undertaken over the past five years 7.5.1 Future Dam Sites has identified a shortlist of preferred options for detailed assessment . In 1988, the Northern Territory and prioritising. Government endorsed the Warrai, Marrakai and Mount Bennett Dams as Detailed hydrological, geophysical, its preferred options for major dams in engineering and environmental studies the Darwin region. A plan of the three will be undertaken over the next two dam sites is shown in Figure 25. years to determine the viability and priority of the shortlisted options. A contemporary review of the three dam sites by Power and Water has Besides new sources of water supply, selected Upper Adelaide River Dam as a range of decentralised integrated the preferred development priority of water management solutions have the three dam sites, based on a range clear potential. These options aim to of economic, social, environmental and reduce reliance on the potable water water quality criteria. system for non-potable uses, and help defer the development of major Of the three dam sites, Upper Adelaide new sources of potable supply. These River Dam is the only site for which the include rainwater tanks, greywater catchment can be closed to the public, reuse and wastewater recycling to as for Darwin River Dam. Closing be implemented over time. Further the catchment may reduce the level discussion is provided in Section 7.6 of treatment required to achieve a Alternative Supply Options. potable supply. Technologies to reduce evaporation can A plan of the future dam sites is help manage water supplies, providing provided (on the following page).

power and water corporation Darwin Region Water Supply Strategy 37

Figure 25: Plan of Future Dam Site Options for the Darwin Region

Manton Darwin River Dam Dam Catchment Catchment Area Area Marrakai Dam (Future) Mount Bennett Dam (Future)

Mount Bennett Dam Catchment Area

Upper Adelaide Marrakai Dam River Dam Catchment Area (Future)

Upper Adelaide River Dam Catchment Area

7.5.1.1 Upper Adelaide River Dam Approximately half of the catchment comprises two land parcels that . The proposed Upper Adelaide River are part of Litchfield National Park. . Dam is located on the Adelaide River, Two other properties make up the . about five km upstream from the town rest of the catchment — Silkwood of Adelaide River. The catchment area Downs, a Crown Lease with very few is approximately 610 square km. The existing improvements, and Tipperary catchment comprises segments from Station, a pastoral lease with current four parcels of land, indicated by the stock operations. hatched areas on Figure 26.

power and water corporation 38 Darwin Region Water Supply Strategy

Figure 26: Proposed Upper Adelaide River Dam Site and Affected Land Parcels

Upper Adelaide River Dam Catchment Area

Proposed new Upper Adelaide River Dam site Sec 94 Conservation Land Corporation (Litchfield Park) Adelaide Approximate River Catchment Area STUART HIGHWAY 72 km2

DORAT ROAD Indicative area subject to inundation Upper Adelaide River Dam (Future) Waters edge at full supply level

Conservation Land Corporation (Litchfield Park) Robin Approximate Falls Catchment Area 185 km2

Adelaide River Silkwood Downs Adelaide River West Branch Approximate Catchment Area 265 km2

Tipperary Station Approximate Catchment Area 88 km2

DALY RIVER ROAD

power and water corporation Darwin Region Water Supply Strategy 39

Power and Water and the Northern 7.5.1.2 Marrakai Dam would require successful negotiations Territory Government have been with members of the Finniss River The Marrakai Dam proposal would investigating potential future dam Aboriginal Land Trust, who are create a very large, shallow reservoir on sites for many years and have custodians of a significant proportion the Adelaide River in the Marrakai area. undertaken various investigations for of the dam’s inundation area. The catchment area is 4,325 square km the Upper Adelaide River Dam site and the reservoir would cover . As a result of a contemporary including: 211 square km with an average . assessment of the three shortlisted • Streamflow monitoring to provide depth of only 3 m. dam options, Mt Bennett Dam is not a an indication of potential yield preferred option for the medium term, In 1990, Cabinet approved acquisition from Upper Adelaide River Dam but will remain an option for further of properties affected by the catchment; assessment in the longer term. inundation area of Marrakai Dam, • Geophysical studies and which at the time, was considered geotechnical investigations to to be the preferred water source provide information about the development option. Land acquisition structural suitability of the land for for the inundation area of Marrakai constructing a dam, and positioning Dam has been completed, with the of the dam wall; land re-leased for a range of low • Land use and erosion studies of the impact uses. catchment; and A significant number of existing • Flood studies. and legacy mines exist within the These previous studies provide Marrakai Dam catchment, resulting Power and Water with confidence in potential water quality risks for any that the Upper Adelaide River Dam future water supply scheme. A dam site is technically suitable for the at this location would impact on a construction of a major dam. Further large proportion of the Adelaide River engineering investigations are required catchment. Moreover, with evaporation however, as well as an assessment of rates forecast to increase significantly the environmental, social and cultural due to climate change, the viability impacts of the dam. Additionally, a of the Marrakai Dam will require contemporary calculation of yield is reassessment should it be prioritised required to be able to assess Upper for development in the future. Adelaide River Dam against other As a result of a contemporary medium term water supply options for assessment of the three shortlisted the Darwin region. dam options, Marrakai Dam is not a Currently, a catchment management preferred option for the medium term, plan is being developed for the Upper but will remain an option for further Adelaide River Dam option, as well as assessment in the longer term. other environmental, hydrological and engineering studies. 7.5.1.3 Mt Bennett Dam The land on which it is proposed Mt Bennett Dam is the third option that Upper Adelaide River Dam be for a dam site in the Darwin region constructed is subject to the Native that was shortlisted in 1988, and Title Act (i.e. Native Title may not is downstream of Batchelor on the be extinguished), and a number of Finniss River. registered and recorded Aboriginal A significant number of existing and sacred sites are known to exist in the legacy mines exist within the Mt catchment and/or the inundation area. Bennett Dam catchment, including the Power and Water has been liaising Rum Jungle Uranium Mine, resulting with the Traditional Owners of the area in potential water quality risks for any through the Northern Land Council, future water supply scheme. and the Aboriginal Areas Protection Authority, as well as landowners in the Development of the Mt Bennett Dam area, to secure permission to access would impact on a large proportion the catchment for the purpose of of the Finniss River catchment. undertaking environmental studies. Development of the Mt Bennett Dam

power and water corporation 40 Darwin Region Water Supply Strategy

7.5.2 Augmentation of Manton • Developing a new dam further car park. Constructing a dam further Dam’s Storage upstream in the catchment, and upstream reduces the impact on maintaining the existing full supply recreation, but is more expensive and Augmenting Manton Dam’s storage level for the existing storage. results in a significantly lower yield provides an opportunity to increase the improvement. yield available from the reservoir. Cost estimates for the augmentation options range from $60 million to $220 The augmentation of Manton Dam will A number of storage augmentation million, which could increase yield by be assessed against other short-listed options have been identified and 5,000 to 15,000 ML/yr. medium term options to augment the investigated for Manton Dam over Darwin region water supply. A number the years. The two main approaches Raising the full supply level at the of hydrological and environmental involve either: existing dam site will maximise the yield potential of the catchment, but studies will be undertaken over . • Raising the full supply level for the will adversely impact the existing the next two years to support . existing storage by constructing a recreational use of the dam by flooding the assessment. new, higher dam at the existing dam existing roads, the boat ramp and the site; or

Figure 27: Manton Dam – Potential Storage Augmentation

Pipeline to Darwin

Extent of Water Manton Surface for Manton Dam Pump Station Dam Raised to FSL 46m AHD

Existing FSL 38.17m Existing FSL Manton Dam 45.86m for Recreation Area for Manton Dam Darwin River Dam Darwin River Dam

NATIVE VEGETATION AREAS Forest or Shrub WATERWAYS Existing Waterways RAILWAYS Line ROADS Existing Roads CATCHMENT Catchment Boundary Existing FSL

PROPOSED WORKS 0 1 2 Proposed FSL (Raised Dam) kilometres Proposed Railway Reinforcement Embankment FSL = Full Supply Level

power and water corporation Darwin Region Water Supply Strategy 41

7.5.3 Adelaide River Off-stream water harvest and off-stream storage River to assess its variability and . Water Storage Scheme scheme could supply up to 50,000 ML/ the sediment load it carries. This . yr to the Darwin region water supply data will help in assessing the An area in the Marrakai region could system. It is likely the scheme would be scheme’s viability and frame any provide off-stream storage adjacent constructed in stages. The study also potential operating strategy. to the Adelaide River of 300,000 ML, a considered the scheme’s potential role volume roughly equivalent to that of The Adelaide River off-stream water in harvesting water from a future Upper Darwin River Dam. The area could store storage scheme will be assessed Adelaide River Dam, whereby water is water harvested from the Adelaide against other short-listed medium released from the Upper Adelaide River River during flood flows in the wet term options to augment the Darwin Dam to the Adelaide River for transfer season. The stored water could then region water supply. A number of downstream. These channel flows be transferred to the Strauss Water hydrological, geophysical, engineering would be in lieu of a pipeline connecting Treatment and Storage Facility for and environmental studies will be Upper Adelaide River Dam with the treatment and distribution. undertaken over the next two years to water supply system. support the assessment. A feasibility study undertaken in Power and Water has commenced 2011, suggested the Adelaide River sampling water quality in the Adelaide

Figure 28: Adelaide River Off-stream Water Storage Scheme

Upgrade existing road to all weather access track Connect to future transmission main Byers Road Bridge over Manton River

Rising main Road

Manton Valley Intake channel Stuart Highway Pipeline and access tunnel

Pump station Manton Dam

Pump station and rising main

Offtake channel Adelaide River off stream water storage Adelaide River FSL. 30m AHD

Marrakai Road All weather access track

All weather LEGEND access track All weather access track Rising main Intake and Offtake channel Pump station

Bridge over Stuart Highway Tunnel Heathers Lagoon Road

FSL = Full Supply Level

power and water corporation 42 Darwin Region Water Supply Strategy

7.5.4 Desalination 7.6.1 Water Sensitive Urban Design 7.6.2 Rainwater Tanks Desalination plants exist in most Water Sensitive Urban Design (WSUD) The marked seasonality of rainfall capital cities in Australia, or are is a contemporary and holistic in the wet/dry tropics is the major planned for development. Whilst the approach to urban development that barrier to take-up of rainwater tanks Top End receives reliable rainfall and aims to minimise impacts on the in urban areas of the Darwin region. this is not expected to change over natural water cycle and protect the Rainwater tanks cannot substitute for time, Power and Water recognises health of aquatic ecosystems. potable water, as a potential source for there are is significant risk in irrigation water in Darwin. Irrigation The principles of WSUD are to: developing surface water supplies. demand is very high during the dry Desalination needs to be part of the • protect and enhance natural water season, but little irrigation occurs suite of water source development systems (creeks and rivers etc.); during the wet season. Large rainwater options being assessed for the . • treat urban stormwater to meet tanks would be needed to capture and medium term. water quality objectives for reuse store enough water during the wet, for use during the dry. Such tank sizes Furthermore, desalination technology and/or discharge to receiving waters; are not feasible for typical urban lots, and operation has improved • match the natural water runoff and are costly. In the wet/dry tropics, significantly in recent times, . regime as closely as possible (where therefore, rainwater tanks are best providing increased efficiencies . appropriate); suited to replacing indoor demands . and reduced environmental impacts. . • reduce potable water demand for water. A contemporary review of the potential through water efficient fittings and for desalination is warranted, and appliances, rainwater harvesting and Despite the high degree of seasonality should be included in Power . wastewater reuse; of rainfall in the Darwin region, and Water’s water source . significant volumes of rainwater can • minimise wastewater generation, development planning. still be harvested during the wet and treat wastewater to a standard season. Rainwater tanks can effectively Power and Water is currently suitable for effluent reuse, and; service high-volume indoor uses, such undertaking a feasibility study into . • integrate stormwater management as washing machines and hot water the use of desalination as a water into the landscape, creating services. The large volumes and high supply option for the Darwin region. . multiple-use corridors to maximise reliability of rainfall during the wet . visual and recreational opportunities. season means rainwater tanks can The study assesses: The recently developed suburb of meet almost all of the demand for • The suitability of Darwin . Bellamack in Palmerston has been . internal water during the wet season. harbour as source water for a used by the Northern Territory This high reliability for up to five desalination plant; Government to showcase WSUD months of the year, compensates for • Requirements for pre-treatment principles. The following initiatives the lack of rainfall during the . and appropriate desalination support WSUD objectives: dry season. technologies; • Three constructed ephemeral 7.6.3 Greywater Reuse • Infrastructure requirements for wetlands which treat stormwater; connecting to the public water • A non-potable water supply Greywater from residential and supply system; reticulation network within the commercial areas (water from the • The logistics of disposing of waste development will supply water for laundry, bathroom taps and shower) streams; and outdoor uses, including irrigation along with industrial greywater (slightly • Energy use and greenhouse gas of public and private landscapes. polluted water reused in manufacturing production. Initially, groundwater will supply the or other industrial processes) is a non-potable reticulation network, potential water source requiring less 7.6 Alternative Supply Options but ultimately recycled wastewater treatment than blackwater (water from from Palmerston Wastewater toilets and kitchen). In addition to the traditional options Treatment Plant will charge the non- for augmenting the Darwin region Greywater contaminants include; low potable water supply reticulation levels of bacteria, faecal matter, organic water supply in the medium term, a network; and range of decentralised integrated water matter, microorganisms, salts and management solutions also warrant • Additional water conservation detergents. All of these contaminants consideration. Such options aim to measures, which are promoted can contribute to colour and odour. reduce reliance on potable water for within all public buildings and public Depending on how it is to be reused, non-potable uses, and help to defer open space, as well as demand greywater may require a high level the development of major new water management within private of treatment, including screening, sources. The options include rainwater dwellings and private open space. sedimentation, biological treatment tanks, greywater reuse and wastewater and disinfection. However, where recycling implemented over time. public access is limited, treatment requirements are lower. For example, . it may be possible to divert greywater

power and water corporation Darwin Region Water Supply Strategy 43

for subsurface irrigation with . 7.6.5 Recycled Wastewater The level of treatment required for a minimal treatment. wastewater recycling scheme varies Power and Water aims to use recycled depending on the end-use of the Reuse of greywater requires that the wastewater when justified on recycled water. The general philosophy greywater is separated from blackwater economic, social and environmental applied in treated wastewater recycling at the source. This may be feasible in grounds. A target has been set for is that wastewater is treated to the new high density developments or the long term: Power and Water aims minimum level required for it to be at individual industrial sites, but it is to reuse 100 per cent of dry weather ‘fit-for-purpose’. For example, some difficult to retrofit existing buildings flows as treated wastewater in all industrial processes, or irrigating open or to apply the technique on a regional wastewater systems. This remains an spaces where there are high levels of scale. Generally speaking, it falls to aspirational target at this time, owing human contact, require a higher level individual households to take up . to cost and logistical constraints. of treatment than uses where public the initiative. The Darwin region has five wastewater access and human contact is limited. treatment plants (WWTP), which 7.6.4 Stormwater Reuse The cost of treating wastewater to service different areas of the collection higher levels is currently much higher Stormwater flows in urban network. The WWTPs are located than the cost of supplying potable environments are higher, more at Ludmilla, Leanyer/Sanderson, water. However, there are a additional frequent and of lower quality than in Palmerston, Berrimah and Humpty benefits from recycling of treated undeveloped catchments. This leads Doo. Over 20,000 ML of treated wastewater, including a reduction to adverse impacts on downstream wastewater is currently discharged of environmental impacts and the waterways. Harvesting stormwater each year to Darwin Harbour from deferral of capital expenditure on flows from a catchment can therefore these plants. additional water sources. benefit downstream waterways by Power and Water operates one removing excess pollutants along with major treated wastewater recycling 7.7 Evaporation Reduction the excess stormwater flows. This scheme in the Darwin region, with Technology environmental benefit is the principal highly-treated wastewater from the driver for stormwater reuse in the Evaporation from Darwin River Dam Northlakes Recycled Water Treatment Darwin region. is responsible for between one half Plant (RWTP) supplied to the Darwin to two-thirds of the total water loss Theoretically, stormwater harvesting Golf Club and Marrara Sports Complex. (water level drop) each year. This could reduce potable water demand. As Approximately 200 ML/yr is supplied loss significantly affects the yield for rainwater tanks however, the slump by the Northlakes RWTP, which is (sustainable annual extraction limit) in demand for irrigation water during operating at its maximum capacity. from the reservoir. If evaporation from the wet season means stormwater Power and Water also uses treatment the reservoir could be reduced, then reuse is less viable than it might be. wastewater in its process train at . more water would be available for Moreover, the treatment required to the Ludmilla WWTP. Approximately extraction. allow non-potable reuse of stormwater 550 ML/yr is currently reused on-site . in the household, means stormwater is There are three main types . at the plant. unlikely to substitute for potable water of evaporation reduction . under most circumstances. A scheme to provide treated wastewater technologies available: to a turf-growing business near the Due to the seasonal nature of rainfall 1. shading the water with shade . Palmerston WWTP has been partially in the Darwin area, significant storage cloth or plastic screens; developed. This scheme would supply would be needed to make captured less than 100 ML/year and is dependant 2. covering the water surface . stormwater viable for irrigation. on a commercial commitment . with floating plastic modular Storage in Darwin can be in storage from the turf farm operators. material; and ponds, storage tanks or via aquifer 3. applying chemical products to storage and recovery. Aquifer storage A study into the viability of a treated the water surface to reduce its involves the pumping of water into wastewater recycling scheme to evaporation potential. a groundwater aquifer during the irrigate public open space in the wet season, and recovering the water northern suburbs of Darwin is being These technologies have been applied again for use during the dry season. undertaken. The study investigates elsewhere on small water storages, Aquifer storage and recovery can be upgrading the Leanyer Sanderson such as farm dams. None of the cost effective and eliminates the loss WWTP to provide high-quality treated available technologies have been of water from storages to evaporation wastewater for recycling. tested on a large-scale potable water during the dry season. However, reservoir like Darwin River Dam. A third pipe system has been installed aquifer storage and recovery is highly at the new suburb of Bellamack in The primary issues affecting the dependent on the underlying geology Palmerston, and is charged with application and effectiveness of the and the nature of the aquifers, and non-potable groundwater. In the long- available technologies are: there are no suitable aquifers in the term, the third pipe will be charged Darwin region. • the impact of seasonal wave . with treated wastewater from the and wind action, and extreme Palmerston WWTP, once additional weather events; treatment is available.

power and water corporation 44 Darwin Region Water Supply Strategy

• the logistics of securing shading or spillway at Darwin River Dam to resource (beyond the current Howard modular floating technologies in increase the full supply level by 1.3m. East Borefield project) is no longer areas which are inaccessible by land, The works increased the capacity of considered to represent a sustainable and the provision of safe access for Darwin River Dam by 20 per cent, option for additional water for the maintenance; and which increased yield. Additional Darwin region water supply system. • the impact on drinking water quality storage augmentation options are resulting from changes in limnology available through further works to 7.8.4 Continued Development of the due to shading, cooling, heating the embankments, spillway and the Howard East Borefield construction of a series of saddle and chemical influence, including The continued development of the dams, however, though these were potential treatment requirements. Howard East Borefield was planned considered in the planning process, to deliver an additional 14,000 ML/ At full supply, Darwin River Dam’s the optimal project was selected yr supply to the Darwin region over surface area is 52 square km and the for construction. The further time. However, with the improved water body is subject to significant augmentation of Darwin River Dam’s understanding of sustainable yield wind and wave action at various times storage is now excluded as an option. during both the wet and dry seasons. from the Koolpinyah aquifer, ongoing significant development of the Howard 7.8.2 Darwin River Dam – Further Whilst some of the technologies East Borefield is no longer considered Extraction Supported by could potentially be applied to only to represent a sustainable option for Water Treatment a proportion of the surface area and additional water for the Darwin region still achieve measurable evaporation Historically, the minimum operating water supply system. savings, covering even a part of the level adopted for Darwin River Dam In the absence of a significant water body offers up significant was 40m AHD . This was to ensure . reduction in other consumptive uses logistical challenges, at extremely high the quality of water extracted from . (horticulture irrigation and private capital and maintenance costs. For the reservoir met the standards for rural residential bores), the continued example, the application of an existing potable water. floating plastic modular technology development of the Howard East to a quarter of the water body of It is likely that the quality of water Borefield, beyond the additional Darwin River Dam is estimated to cost available from Darwin River Dam will development identified for 2014/15 to hundreds of millions of dollars . deteriorate as it becomes necessary increase emergency supply provisions to operate the dam at lower levels and to improve the reliability of Water utilities, mining companies . than have occurred in the past. The extracting Power and Water’s current and researchers around the country development of water treatment licensed groundwater allocation, is are undertaking both small and larger capabilities for the Darwin water excluded as an option. scale trials, and manufacturers are supply system could allow Power and responding with further product Water to safely draw water from below 7.8.5 Alternative Dam Sites development. Power and Water is the previously set minimum operating In the 1980s at least three alternative closely monitoring the continuing level, providing opportunity to increase dam sites (additional to the three . development and testing of the . the previously assessed yield. various evaporation reduction that were eventually shortlisted) . technologies. Whilst it is unlikely However, the recent adoption of the were considered. that an appropriate evaporation targeted level-of-service objectives for Figure 29 (right) identifies the location reduction technology will be available the Darwin region relies on the whole of three previously-considered dam for application to Darwin River of the extractable volume of Darwin sites: Tumbling Waters, Acacia Gap Dam within the next five years, River Dam being available as working and Batchelor. In 1990 the Northern this may represent a viable supply volume, drought response reserve, Territory Government considered the augmentation option in the . or contingency storage, to assure relative risks and benefits associated medium term. adequate water security for the Darwin with these sites and selected three region. As such, the option to increase dam sites (Upper Adelaide River, 7.8 Excluded Options yield, by more fully utilising Darwin Marrakai and Mt Bennet) to be taken River Dam’s storage combined with . forward in Power and Water’s water Over the past two decades, numerous the provision of water treatment has source planning. The other sites were water source development options been nullified. have been considered as part of a long discounted for a range of reasons including potential environmental, term planning process. The following 7.8.3 Lambell’s Borefield section briefly lists and describes the engineering, economic, social and major options that have been excluded Lambell’s Borefield, on the Koolpinyah water quality impacts. from the current strategy. Aquifer in the Humpty Doo area, was once suggested as a potential 7.8.1 Darwin River Dam Storage drinking water supply source. The Augmentation water resource in this area is part of the Koolpinyah Aquifer which is likely In 2010, Power and Water completed to be already over extracted. As such, the upgrade of embankments and additional development of this

power and water corporation Darwin Region Water Supply Strategy 45

Figure 29: Previously Considered Dam Sites

Darwin

Stuart Highway McMinns and Howard Palmerston East Borefields

Adelaide River Humpty Doo

Arnhem Highway

Acacia Gap Dam Tumbling Waters Dam

Manton Reservoir Darwin Marrakai Finniss River Dam River Reservoir Mount Bennet Dam

Batchelor Dam

Batchelor

Upper Adelaide River Dam Adelaide River

power and water corporation 46 Darwin Region Water Supply Strategy

7.8.6 Existing Dams and Lakes 7.8.7 Hanna’s Pool on the Finniss River A number of small dams and lakes exist in the Darwin region, such as Lake An interbasin transfer scheme (Hanna’s Bennett. Many of these storages are Pool) identified in the 1980s, whereby privately owned, have significant water flood flows would be harvested from quality challenges and are not large the Finniss River for transfer to the enough to provide an economically Darwin River Dam was the subject of a viable water source option for the feasibility study in 2011. Darwin region water supply system, Given the assumptions for given the significant connection costs environmental flows that were applied, associated with their remoteness from the study found there was insufficient the water supply network. water available for the scheme to be an economically-viable source for the Darwin region water supply system.

power and water corporation Darwin Region Water Supply Strategy 47

8 Development of plans

8.1 Demand/Supply Model • forecast industrial demand growth; investment. Successful demand management will be essential to Integral to the Strategy is the • achievement of the Living . defer the need to develop new sources development and ongoing refinement Water Smart water demand . of water for as long as possible. and review of a long-term demand/ savings targets; Decentralised integrated water supply model. The model relies on a • climate change-driven demand management solutions will likely be range of key parameters including: growth (based on temperature and a key tool in reducing demand on the evaporation increases); • source (surface water and potable water supply system over time. groundwater) yields; • climate change-driven yield Power and Water recognises that the • base demand (total production); reductions from sources (largely due to increased evapotranspiration); water demand savings targeted by • demand growth (organic and Living Water Smart are ambitious and • a 10 per cent headroom requirement incremental); require sustained community and (buffer) between demand and Government support. As a prudent • climate change impacts (on both supply; and demand and supply); and way to manage risk, Power and Water • programmed development of water is continuing the planning and design • demand management outcomes. source projects. work required to return Manton Dam The values attributed to each of these Figure 30 (on the following page) to service and to find additional future key parameters are subject to varying represents Power and Water’s current sources of water. This will allow the levels of confidence, with the greatest water source development programme programme to be fast tracked should uncertainty surrounding the impacts and indicates that the supply system growth in water demand outpace of climate change and the outcomes of will be subject to a reduced level of demand management. demand management. service (increased likelihood of water Illustrated in Figure 31 (on the Power and Water’s demand/supply restrictions) at times, as demand following page), the alternative model has been developed and refined encroaches on the 10 per cent programme represents the earliest over the past three years and has . headroom requirement ahead of achievable timeline, considering the capability to test sensitivities for programmed source augmentation. the significant engineering and key parameters. It is intended that The current programme identifies the environmental studies and approvals the key parameters in the model be further development of the Howard that are required, and making reviewed regularly, so as to incorporate East Borefield in 2014/15, the return allowance for construction. The the latest and most accurate to service of Manton Dam in 2025 alternative programme assumes . information available. and the connection of the preferred 50 per cent of the Living Water . (but yet to be selected) medium-term Smart demand management . 8.2 Demand Driven Water Source supply augmentation option beyond targets are achieved. Development Programme 2030. The programme is subject to key Power and Water aims for its capital planning assumptions, including the works programme to deliver the base realisation of the Living Water Smart case – a demand-driven water source water demand savings targets. development programme. A new major water supply source Power and Water’s base case demand/ such as Upper Adelaide River Dam supply model scenario incorporates: could cost in excess of $500 million to develop and connect to the water • system yield based on the targeted supply system. Capital investment of level-of-service objectives; that magnitude will have a significant • forecast general demand growth impact on water pricing in the region, (PWC base demand); in order to recover the costs of the

power and water corporation 48 Darwin Region Water Supply Strategy

Figure 30: Current Water Source Development Programme

Industrial Step Demands Demand Projection Based On PWC BASE - 1.45 % Residential Demand Management: -20.60% Total by 2018 Historical Demand Industrial Demand Management: -21.60% Total by 2018 Supply Capacity Climate Change Impact on Demand: +2.66% Total by 2030 10% headroom requirement infringed Climate Change Impact on Supply: -10.00% Total by 2030 Augmentation Dates

100,000

50,000 Manton Dam - Return to Service Howard East Borefield - Further Development Darwin River Dam - Raise FSL Howard East Borefield Consumption (ML/annum) 2001/02 2010/11 2014/15 2025/26 0 1999/00 2004/05 2009/10 2014/15 2019/20 2024/25 2029/30 Year

Figure 31: Alternative Programme – For Planning and Design Purposes

Industrial Step Demands Demand Projection Based On PWC BASE - 1.45 % Residential Demand Management: -10.30% Total by 2018 Historical Demand Industrial Demand Management: -10.70% Total by 2018 Supply Capacity Climate Change Impact on Demand: +2.66% Total by 2030 10% headroom requirement infringed Climate Change Impact on Supply: -10.00% Total by 2030 Augmentation Dates

100,000 Next Water Source Manton Dam - Return to Service 50,000 Howard East Borefield - Further Development Darwin River Dam - Raise FSL Howard East Borefield Consumption (ML/annum) 2001/02 2010/11 2014/15 2017/18 2025/26 0 1999/00 2004/05 2009/10 2014/15 2019/20 2024/25 2029/30 Year

power and water corporation Darwin Region Water Supply Strategy 49

8.3 Capital Expenditure emergency supply capacity, and Funding of $30 million has been Programme enhancing redundancy so as to reliably allocated to construct additional water extract Power and Water’s existing storage at the Strauss Water Treatment Power and Water’s short term capital licensed groundwater allocation. Facility. The staging of storage expenditure programme is identified development depends on load growth in its Statement of Corporate Intent, The major components of the Manton in the area. an annual publication identifying Dam return to service project total Power and Water’s strategies, risks, $161.5 million, including the Strauss Also, $21.4 million has been allocated investment plans and performance Water Treatment Facility and storage. to construct a new pumping station at targets. Table 13 details Power and Darwin River Dam, to meet increasing During the next two years, there Water’s capital investment programme peak-day demand pumping, and to will be opportunity to review the for water source planning and manage risk over time. assumptions influencing the timing of development. capital expenditure on Manton Dam’s Hydrological, engineering, geophysical The programme identifies the further return to service, including growth in and environmental studies are . development of the Howard East demand and the outcomes of demand being undertaken for a range Borefield and the return to service of management. The construction costs of medium-term water source Manton Dam as the significant water identified in the programme are development options, and are . source development investments in order-of-cost estimates only. Project funded from a $4 million allocation . the short term. development and design over the . to strategic planning. next two years will firm up these The cost of further developing . estimates, allowing the programme . the Howard East Borefield is . to be updated accordingly. $15.6 million, providing increased

Table 13: Capital Investment Programme – Water Source Development Projects

Description of Works Total Howard East Borefield - Stage 2 $15.6 Strauss Water Treatment Facility $70.0 Bulk Water Storage at Strauss $30.0 Darwin River Dam - New Pump Station $21.4 Manton Dam Transmission Main $51.0 Manton Dam - Upgrade Pump Station / Intake $10.5 Long Term Water Source Strategy Works $4.0 TOTAL ($ Millions) $202.5

Works Category EMERGENCY SUPPLY TREATMENT AND STORAGE WATER SOURCE AUGMENTATION STRATEGIC PLANNING

power and water corporation 50 Darwin Region Water Supply Strategy

9 Management of risk and uncertainty

The inherent difficulty of planning strategies will be pursued, with a view established management zones for a 20-year period means plans and to recommending measures for water around these bores to help reduce risk strategies need to be flexible to adapt supply planning. of contamination. to changing circumstances in the Planned further development of the future. This section outlines some of 9.3 Impact of Government Policy Howard East Borefield to provide the major uncertainties associated Water allocation planning in the redundancy in Power and Water’s with long-term water resource Darwin region may impact on Power groundwater supply, may present an planning, and the measures that have and Water’s licensed extraction from opportunity to partially shift Power been implemented to manage these water resources. and Water’s regular extraction away uncertainties. from the McMinn’s Borefield, further The water allocation planning process reducing contamination risks. 9.1 Water Demand Growth formally commenced in 2010 in the Koolpinyah (Howard East) Aquifer . Surface water catchments present a Power and Water recognises the with the formation of the Howard . number of significant risks with the difficulty of calculating statistically- East Water Advisory Committee. . potential to detrimentally affect the accurate projections of growth beyond The groundwater resource is quality of water drawn from dams. five years. This is due to the range of considered to be under stress, and These risks include illegal access to the factors that influence water demand, current extraction may be exceeding catchment, erosion and flood damage, prompting the analysis of historical sustainable levels. The water allocation bush fires, feral animals and weeds. trends, and the development of planning process is expected to limit forecasts using up-to-date local and The detection of the aquatic weed extraction to sustainable levels, and regional information. Cabomba downstream of Darwin to achieve an equitable share of the River Dam in the Darwin River in The growing focus on water resource for each stakeholder, whilst 2004, triggered a significant weed conservation and an emphasis on providing for environmental and eradication action plan by the finding new ways to save water, are cultural water requirements. Northern Territory Government. driving the need for better demand Power and Water is active in the . Whilst occurrences of Cabomba have forecasting and analysis tools. Power water allocation planning process . since reduced significantly, an active and Water recognises the importance for the Darwin region and will . monitoring and quarantine regime of understanding details and patterns continue to work closely with DLRM continues. of use at the customer’s tap. to ensure public water supply is at the Power and Water regularly reviews its Over the next three years, Power and forefront of water resource planning catchment management activities Water aims to improve its demand and allocation. to protect source water quality. Some modelling and forecasting capabilities. Environmental policy initiatives have of the most important activities the potential to impact on water include river health works, biodiversity 9.2 Impacts of Climate Change source development planning and management, fire prevention and An area of uncertainty within the project development. Power and property management. planning horizon is climate change. Water will liaise closely with DLRM Power and Water has developed Modelling climate change has and Government over existing and a Catchments and Water Source identified significant impacts on yields proposed initiatives to ensure the Protection Strategy to support the that are likely to be available from Darwin region water supply remains proactive management and protection surface water storages in the Darwin sustainable in the long term. of its water supply catchments. region by 2030. 9.4 Catchment Risks The nature and severity of future climate change will clearly have A number of significant catchment- implications for the Darwin region related risks have the potential to water supply system. Power and impact on the Darwin region water Water will continue to monitor the supply’s sources. impacts of climate change, and plan In the McMinns Borefield, land for it using the best available scientific adjacent to Power and Water’s water information. supply bores has been developed for Power and Water will model impacts rural residential and horticultural on yields in line with new regional land uses. These land uses pose a climate change information as it risk of contamination to the public becomes available. Also, adaptation water supply. Power and Water has

power and water corporation Darwin Region Water Supply Strategy 51

10 Stakeholder consultation

Delivering the Strategy in the most The outcomes of community debate, Manton Dam, once the timing of the effective way, will require consultation measured changes to customer water- project is resolved. The stakeholder with stakeholders and managed use, regulatory direction and updated engagement phase for these projects communications. climate change data as it comes to will directly influence their design and hand, will be used to inform the next implementation. The development of the Strategy has issue of the strategy in approximately been informed in part by the results five years. of Power and Water’s 2005 survey of community attitudes to water use. Detailed stakeholder engagement plans will be developed for individual The Strategy is intended to provide . water source development projects. a basis for community debate . The projects include the further over the next few years around development of the Howard East demand management and water Borefield and the return to service of source development.

power and water corporation 52 Darwin Region Water Supply Strategy

11 References

Darwin Region Water Supply – Level of Water Sensitive Urban Design – Darwin Rural Area South - Water Service Objectives, SMEC, 2012 Practical Guide, Department of Land Supply Development Master Plan, Planning, 2009 GHD, 1996 Darwin Yield Assessment and Multi- Objective Decision Support System Water Sensitive Urban Design – Darwin Regional Water Supply and Volume 3 – Multi-Objective Decision Rainwater Tank Discussion Paper, Land Management Strategy, Northern Support System, SMEC, 2012 Department of Land Planning, 2009 Territory Government, 1988 Darwin Yield Assessment and Multi- Survey Outcomes, Community Manton Dam Transfer Feasibility Study, Objective Decision Support System Attitudes to Water Use, Power and Gibb Australia, 1985 Volume 2 – Manton Dam Return to Water Corporation, 2006 Finniss River Dam and Diversion Service and Upgrade Options, SMEC, Framework for Urban Water Resource (Hanna’s Pool) Studies, Gibb Australia, 2012 Planning, Water Services Association of 1982 Darwin Yield Assessment and Multi Australia (WSAA), 2005 Objective Decision Support System Guidelines for the Development of Volume 1 – Review of Yield, SMEC, 2011 a Water Supply Demand Strategy, Interbasin Transfer Options Study Department of Sustainability and for the Darwin Water Supply System, Environment, Victoria, 2005 SMEC, 2011 Darwin Water Story, Power and Water Planning Guidelines for Water Corporation, 2005 Supply and Sewerage, Queensland Darwin Bulk Water Strategy, ARUP, Department of Environment and 2004 Resource Management, 2010 Western Manton Dam Study, SMEC, Power and Water Corporation 2000 Supplements for the Planning Guidelines for Water Supply and Water Resources for the Greater Sewerage, Power and Water Darwin Area - Darwin Water Resources Corporation, 2010 Strategy, Power and Water Authority, 1999 Territory 2030 Strategy – Northern Territory Government, 2009

power and water corporation Darwin Region Water Supply Strategy 53

Appendix 1: Land tenure and land zoning maps for Darwin region water supply catchments

power and water corporation 54 Darwin Region Water Supply Strategy

Darwin River Dam and Manton Dam Land Tenure LEGEND

Dams

Dam Catchment

Roads Major

C O TENURE REFERENCE TYPE X P E N IN Freehold S U LA R Crown Lease Perpetual O AD Vacant Crown Land

Government

Perpetual Pastoral Lease

Reserve

Darwin River Dam

Manton Dam

Y

A

W

H

G I

H

T

R

A

U

T

S

0 1.25 2.5 5 Kilometers

power and water corporation Darwin Region Water Supply Strategy 55

Darwin River Dam and Manton Dam Land Tenure LEGEND

Dams

Dam Catchment

Roads Major

C O TENURE REFERENCE TYPE X P E N IN Freehold S U LA R Crown Lease Perpetual O AD Vacant Crown Land

Government

Perpetual Pastoral Lease

Reserve

Darwin River Dam

Manton Dam

Y

A

W

H

G I

H

T

R

A

U

T

S

0 1.25 2.5 5 Kilometers

power and water corporation 56 Darwin Region Water Supply Strategy

Darwin River Dam and Manton Dam Land Zoning LEGEND

Roads Major

Dam Catchment

Dams

D A Zone Description O R Agriculture

A L Commercial CO SU IN Community Living X P EN Community Purpose

Conservation

Future Development

Horticulture

Light Industry

Main Road

S Multiple Dwelling T U A No Planning Scheme Controls

R T Organised Recreation

H

I G Proposed Main Raod

H W Public Open Space

A Rural Y Rural Living Darwin River Dam Rural Residential Manton Dam Service Commercial

Single Dwelling

Specific Use

Tourist Commercial

Utilities

Water Management

0 1.25 2.5 5 Kilometres

power and water corporation Darwin Region Water Supply Strategy 57

Darwin River Dam and Manton Dam Land Zoning LEGEND

Roads Major

Dam Catchment

Dams

D A Zone Description O R Agriculture

A L Commercial CO SU IN Community Living X P EN Community Purpose

Conservation

Future Development

Horticulture

Light Industry

Main Road

S Multiple Dwelling T U A No Planning Scheme Controls

R T Organised Recreation

H

I G Proposed Main Raod

H W Public Open Space

A Rural Y Rural Living Darwin River Dam Rural Residential Manton Dam Service Commercial

Single Dwelling

Specific Use

Tourist Commercial

Utilities

Water Management

0 1.25 2.5 5 Kilometres

power and water corporation 58 Darwin Region Water Supply Strategy

McMinns and Howard East Borefields Land Tenure LEGEND

Existing Power and Water Production Bores

Proposed Power and Water Production Bores

Wellhead Protection Zone

Rivers Lakes

Roads Major

TENURE REFERENCE TYPE

Crown Lease Perpetual

Crown Lease Term

Freehold

Government

Perpetual Pastoral Lease

Reserve

Special Purposes Lease

Vacant Crown Land

GIRRAWEEN ROAD

S T U A R T H IG H W A

Y

ARNH EM HIGH 0 0.5 1 2 Kilometres WAY

power and water corporation Darwin Region Water Supply Strategy 59

McMinns and Howard East Borefields Land Tenure LEGEND

Existing Power and Water Production Bores

Proposed Power and Water Production Bores

Wellhead Protection Zone

Rivers Lakes

Roads Major

TENURE REFERENCE TYPE

Crown Lease Perpetual

Crown Lease Term

Freehold

Government

Perpetual Pastoral Lease

Reserve

Special Purposes Lease

Vacant Crown Land

GIRRAWEEN ROAD

S T U A R T H IG H W A

Y

ARNH EM HIGH 0 0.5 1 2 Kilometres WAY

power and water corporation 60 Darwin Region Water Supply Strategy

McMinns and Howard East Borefields Land Zoning LEGEND

Existing Power and Water Production Bores

Proposed Power and Water Production Bores

Wellhead Protection Zone

Rivers Lakes

ZONE DESCRIPTION

Agriculture

Commercial

Community Purpose

Conservation

Future Development

Horticulture

Light Industry

Main Road

Multiple Dwelling

No Planning Scheme Controls

Organised Recreation

Proposed Main Raod

Public Open Space

Rural GIRRAWEEN ROAD Rural Living

Rural Residential

Service Commercial

Single Dwelling

Specific Use

Tourist Commercial

Utilities

Water Management Y A W ARNH IG H EM

H H IGHW

T AY UA R

0 0.5 1 2 KilT ometres S

power and water corporation Darwin Region Water Supply Strategy 61

McMinns and Howard East Borefields Land Zoning LEGEND

Existing Power and Water Production Bores

Proposed Power and Water Production Bores

Wellhead Protection Zone

Rivers Lakes

ZONE DESCRIPTION

Agriculture

Commercial

Community Purpose

Conservation

Future Development

Horticulture

Light Industry

Main Road

Multiple Dwelling

No Planning Scheme Controls

Organised Recreation

Proposed Main Raod

Public Open Space

Rural GIRRAWEEN ROAD Rural Living

Rural Residential

Service Commercial

Single Dwelling

Specific Use

Tourist Commercial

Utilities

Water Management Y A W ARNH IG H EM

H H IGHW

T AY UA R

0 0.5 1 2 KilT ometres S

power and water corporation Contact us

Call 1800 245 092. Email [email protected]. Visit powerwater.com.au. Follow PowerWaterCorp on Twitter. ABN 15 947 352 360

Head office

Level 2, Mitchell Centre. 55 Mitchell Street, Darwin. GPO Box 1921. Darwin NT 0801

Customer service centres

Shop 28, Ground Floor, Mitchell Centre. 55 Mitchell Street, Darwin

Shop 21, Palmerston Shopping Centre. 10 Temple Terrace, Palmerston

Ground Floor, Government Centre. 5 First Street, Katherine

Shop 8, Alice Plaza. 36 Todd Mall, Alice Springs