East Gippsland Water
8 April 2010
Mallacoota Water Supply Demand Strategy Mallacoota Water Supply Demand Strategy AECOM
Mallacoota Water Supply Demand Strategy
Prepared for East Gippsland Water
Prepared by
AECOM Australia Pty Ltd Level 9, 8 Exhibition Street, Melbourne VIC 3000, Australia T +61 3 9653 1234 F +61 3 9654 7117 www.aecom.com ABN 20 093 846 925
8 April 2010
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Quality Information
Document Mallacoota Water Supply Demand Strategy
Ref
Date 8 April 2010
Prepared by L Dragicevich
Reviewed by Steven Wallner
Revision History
Authorised Revision Revision Details Date Name/Position Signature
A 14- Jan- Draft Document Elisa Hunter 2010 Principal Consultant B 29-Jan-2010 Final Draft Document Elisa Hunter Principal Consultant C 08-Apr-2010 Final Document Andrew Grant Original Signed Associate Director
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Table of Contents Executive Summary i 1.0 Introduction 4 1.1 Regional Setting 4 2.0 Current Water Supply 5 2.1 Description of Water Supply System 5 2.1.1 Surface Water Extraction 5 2.1.2 Groundwater Extraction 5 2.1.3 Water Treatment Plant 6 2.2 Allocation of Water 7 2.2.1 Bulk Water Entitlements 7 2.2.2 Groundwater Licences 7 2.3 Level of Service Objectives 8 2.4 Historical Water Restrictions 8 3.0 Previous Studies, Legislation and Regulation 9 3.1 Previous Long Term Planning Studies 9 3.1.1 Drought Response Plan for Mallacoota (SKM, 2003) 9 3.1.2 EGW Water Supply Demand Strategy (SKM, 2007) 9 3.1.3 Licence Increase Application – Groundwater Licence 9016496 (GHD, 2008) 9 3.2 Regulations and Legislation 9 3.2.1 Surface Water Caps 9 3.2.2 Streamflow Management Plans 10 3.2.3 Groundwater Caps 10 3.2.4 Regional River Health Strategy 11 3.2.5 Heritage Rivers 11 3.2.6 Victorian River Health Strategy 11 4.0 Water Demand 12 4.1 Current Demand 12 4.1.1 Unaccounted Water 12 4.1.2 Non-residential Water Use 13 4.1.3 Summary of Current Demand 13 4.2 Forecast Water Demand 14 4.2.1 Population Projections in the Previous WSDS 14 4.2.2 Census Data 14 4.2.3 Victoria in Future Data 14 4.2.4 East Gippsland Shire Council 14 4.3 Summary of Demand Projections 15 5.0 Demand Management 16 5.1 Measures to Achieve Demand Reduction Targets 16 5.1.1 Current Demand Reduction Initiatives (SKM, 2007) 16 5.1.2 Future Demand Reduction Initiatives (SKM, 2007) 17 6.0 Water Supply 19 6.1 Future Reliability of Surface Water 19 6.1.1 Impact of Climate Change 19 6.1.2 Step Change 19 6.1.3 Impact of Bushfires 20 6.1.4 Forestry 21 6.2 Future Reliability of Groundwater 21 6.2.1 Long Term Reliability and Climate Change 21 6.2.2 Short Term Reliability 22 7.0 Reliability of Supply 23 7.1 Current Reliability of Supply 23 7.1.1 Model Limitations 23 7.1.2 Sensitivity to Groundwater Supply Capacity 24 7.1.3 Setting Restriction Triggers 24 7.2 Future Reliability of Supply 29
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7.2.1 Summary of Future Reliability of Supply 29 8.0 Alternative Water Supply Options 35 8.1 Surface Water 35 8.1.1 Qualification of Rights on the Betka River 35 8.1.2 Water Trading 35 8.1.3 The Genoa River 35 8.1.4 Brackish Water or Seawater 36 8.2 Groundwater 37 8.2.1 Additional Groundwater Bores 37 8.2.2 Managed Aquifer Recharge 37 8.3 Demand Management 38 8.3.1 Auditing High Water Users 38 8.3.2 Foreshore Caravan Park 38 Alternative Water Supply 38 Changing Water Use Behaviour 39 8.4 Improve System Performance 39 8.4.1 Water Loss Reduction 39 8.4.2 Increase Storage 39 8.4.3 Increase System Capacity 39 8.4.4 Treatment Plant Capacity 40 8.4.5 Optimising System Performance 40 8.5 Recycled Water (from the wastewater treatment plant) 40 8.6 Rainwater 41 8.7 Stormwater 41 8.8 Water Cartage 41 8.9 Options to be Considered Further 42 9.0 Assessment of Supply Options using MCA 43 9.1 Selection of Criteria 43 9.2 Scoring 43 9.3 Weightings 43 9.4 Results 44 9.5 Discussion 46 9.5.1 Water Supply Augmentation 46 9.5.2 Emergency Supply 47 9.6 Expected Scheme Costs 47 10.0 Stakeholder Consultation 49 11.0 Conclusions and Recommendations 50 11.1 Conclusion 50 11.2 Summary of Recommendations 50 Appendix A Review of Groundwater Data A Existing Conditions a-1 Impacts from Climate Change a-1 Reliability of the Aquifer a-2 Appendix B Modelling Methodology and Assumptions B Appendix C Additional Modelling Results C
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Executive Summary Water Supply Demand Strategies (WSDS) aim to ensure that an appropriate balance is maintained between urban water supply and demand over the long term planning horizon of 50 years. East Gippsland Water (EGW) finalised their WSDS for all water supply systems during 2007 and is in the process of reviewing the strategies for water supply systems that are experiencing critical shortages. AECOM Australia Pty Ltd (AECOM) has been engaged by EGW to revise their existing WSDS for the Mallacoota water supply system.
Objectives EGW has set level of service (LOS) objectives for water supply reliability. The objectives state that: x Moderate restrictions (Stages 1 & 2) are not desired more frequently on average than 1 year in 10; and x More severe restrictions (Stages 3 & 4) are not desired more frequently than 1 year in 15.
These LOS objectives have been used as a basis for assessing the adequacy of Mallacoota’s current water supply system for meeting current and future water demand.
Reliability of supply With scientific evidence suggesting that climate change is tracking along the driest of scenarios, it is likely that the Betka River will not provide a reliable source of water for Mallacoota into the future. In addition there is significant uncertainty around how groundwater supplies will be impacted by climate change. A number of modelling scenarios were used to determine EGW ability to meet its LOS objectives in Mallacoota. The results showed that the LOS objectives can be met under a high impact scenario (continuation of low flows and high population growth) by the continued reliance on groundwater. Preliminary evidence suggests (refer to Appendix A) that the licensed extraction volume of groundwater of 120 ML per year is within the sustainable yield of the aquifer. However, the data also shows that the groundwater levels have declined over the last 3 years. This observed decline, combined with the likelihood that the recharge rate will be affected by climate change, creates significant uncertainty about the reliability of groundwater in the long term. It is recommended that EGW continue to use groundwater as an integral part of supply to Mallacoota and closely monitor and review groundwater level data. If groundwater does become an unreliable source, EGW should review this WSDS and re-evaluate the options presented in this strategy to secure Mallacoota’s supply.
Alternative Supply Options A number of water supply options have been identified for Mallacoota, which can be described as either supply augmentation options or emergency supply options. The following supply augmentation options will be considered further: x Option 1 – Install additional groundwater bores and seek an increase in the groundwater extraction license x Option 2 – Managed Aquifer Recharge x Option 3 - Demand management for high water users x Option 4 – Cover the raw water storage x Option 5 - Supply additional recycled water to the Golf Course x Option 6 – Supply recycled water to other customers x Option 7 – Supply an alternative water source (rainwater/groundwater) to the Caravan Park
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In addition to the supply augmentation options listed above, the following emergency supply options will also be considered in the multi criteria analysis (MCA): x Water carting x Mobile desalination
Options that were identified and not considered viable include: x Extracting water from the Genoa River due to the length of pipeline required to connect these sources to the existing supply system and poor reliability during dry periods x Accessing the deep pools on the Betka River should only be considered as a last resort and is unlikely to provide significant additional supply x Additional surface storage would provide minimal additional reliability and would therefore not be cost effective x The cost of retrofitting households to supply rainwater is not expected to be cost effective x The infrastructure required for a stormwater harvesting scheme is not considered to be cost effective x Increasing the capacity of the pumps, pipeline and treatment to the bulk entitlement level is not expected to provide much benefit due to the decreasing reliability of the river.
Proposed Scheme The proposed scheme to improve reliability of supply to Mallacoota is: x Improve reliability of supply by: - Completing water use audits of high water users to identify potential water efficient projects - Investigating the possibility of supplying additional recycled water to the golf course - Constructing new groundwater bores - Increasing EGW’s groundwater licence to 220 ML/yr - Covering the raw water storage if funding is granted - Supplying an alternative water source to the caravan park x Provide emergency supply by: - Water carting
Following this update of the WSDS for Mallacoota, it is recommended that EGW action the following strategies for the Mallacoota water supply system. Implementing all of these recommendations will be resource intensive and EGW should prioritise implementation in accordance with the action plan on the following page.
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Mallacoota Water Supply Action Plan Action Implementation Monitor groundwater levels in accordance with the BE requirements and assess long term Immediate trends in groundwater levels. If levels continue to decline across the aquifer, this WSDS should be reviewed as higher cost supply alternatives may become viable. Apply to increase the existing groundwater licence to 220 ML/yr Immediate Seek to reduce current water demand by auditing high water users in Mallacoota and Immediate identifying possible savings Identify supply sources for water carting and if appropriate, formalise emergency access into Immediate the existing bulk entitlement Investigate whether an initial Managed Aquifer Recharge feasibility assessment could be Immediate cost effectively combined with ongoing groundwater investigations at Mallacoota Update Mallacoota’s Drought Response Plan Immediate Continue the current practice of extracting water from the Betka River during times of flow Ongoing Continue to use groundwater as an integral part of Mallacoota’s water supply by constructing Ongoing new bores to ease the pressure on the existing bores and also investigate the potential for a drought relief bore Document the operational procedures for the Mallacoota system and review on an annual Ongoing basis to identify and monitor opportunities for improving the performance of the system. Continue existing leak detection programs to ensure the system operates in an efficient Ongoing manner. Continue to seek a reduction in the area to be logged within Mallacoota’s water supply Ongoing catchment Evaluate the feasibility of a regional mobile desalination plant upon completion of the July 2010 remaining WSDS’s Investigate the feasibility of providing either groundwater, rainwater or a combination of both 2011 to the Caravan Park to reduce their reliance on mains water particularly during peak periods Investigate the feasibility of providing additional recycled water to the golf course 2011 Cover the raw water storage if funding is secured Longer term
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1.0 Introduction Water Supply Demand Strategies (WSDS) aim to ensure that an appropriate balance is maintained between urban water supply and demand over a long term planning horizon of 50 years. East Gippsland Water (EGW) finalised their WSDS for all water supply systems in 2007 and is in the process of reviewing the strategies for water supply systems that are experiencing critical shortages resulting from the combined impacts of the ongoing drought, climate change and bushfires. WSDS are otherwise required to be reviewed and updated every 5 years. Continuing dry conditions has resulted in a significant drop in streamflow rights across Victoria and East Gippsland has not been exempt from these impacts. CSIRO has determined that climatic conditions are tracking above the previous high climate change scenarios, which suggests that the medium climate change scenario that was recommended by Department of Sustainability and Environment (DSE) during preparation of the earlier WSDS may over estimate long term yields. Over recent years streamflow in the Betka River has become increasingly unreliable and reliance on groundwater to provide water to Mallacoota has increased. For this reason the WSDS for Mallacoota is being revised. This document forms a revised WSDS for the Mallacoota water supply system and will replace the strategy set out for Mallacoota in EGW’s overall WSDS (Chapter 10). Where possible this strategy has been prepared in accordance with the DSE’s Guidelines for the Development of a Water Supply Demand Strategy (DSE, 2005), however it is recognised that some of these guidelines are now out of date, particularly with regard to climate change.
1.1 Regional Setting Mallacoota is a coastal town located approximately 190 km east of Bairnsdale in the eastern corner of East Gippsland Shire, near the New South Wales border. The township of Mallacoota is located on the mouth of the Mallacoota inlet. Access to Mallacoota is via Mallacoota Road, approximately 22km from the Princes Highway at Genoa through the Croajingolong National Park. Mallacoota is a relatively small township with a permanent population of around 1,000 people. It is a popular holiday location during the Easter and the summer holidays and experiences large surges in population at these times. The location of Mallacoota is shown in Figure 1.
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Figure 1: Locality Plan (Google Earth)
2.0 Current Water Supply
2.1 Description of Water Supply System Mallacoota is supplied with surface water from the Betka River. Groundwater from two groundwater bores is used to supplement the supply during low flow periods in the Betka River, which has become increasingly common. Supply from groundwater and surface water over the last 3 years is shown in Table 1.
Table 1: Supply from Groundwater and Surface Water Financial Year Groundwater Supply Surface Water Supply 2006/07 45% 55% 2007/08 25% 75% 2008/09 59% 41% 2009/10 (estimate) 74% 26%
2.1.1 Surface Water Extraction Surface water is pumped from the Betka River at a maximum rate of 1.2 ML/day via a 6 km long 150 mm diameter asbestos cement rising main to a 41 ML raw water storage at the water treatment plant. Surface water is pumped from a pumping pool on the river up to a balancing tank by a submersible pump, before being transferred to the treatment plant by a larger pump station. The maximum rate of water transfer is limited by the transfer infrastructure (pipeline and pump station), which prevents the system from delivering the maximum daily bulk entitlement from the river when it is flowing (1.55 ML/day).
2.1.2 Groundwater Extraction When the Betka River ceases to flow, groundwater is extracted from one of two groundwater bores as long as there is capacity in the raw water storage. One of the groundwater bores is located near the Betka River surface water offtake and the other near the treatment plant. Groundwater from the offtake bore is pumped to the treatment plant via the same pipeline that transfers surface water to the treatment plant. The treatment plant bore and offtake bore are fitted with pumps with capacities of 12 L/s and 7.4 L/s respectively. The long term pumping rate of the two bores was assessed in 2000 and it was concluded that the bores could be pumped continuously at 6 L/s for 60 days (Geo-eng, 2000). The report suggested that it would be preferable to
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operate the bores on a 24 hour cycle of 16 hours pumping and 8 hours recovery, allowing for partial groundwater recovery and a longer period before maximum drawdown is reached (i.e. longer than 60 days). Review of recent groundwater extraction rates indicate that the treatment plant bore was providing 0.55 ML/day over a 60 day period, while the Betka bore was providing approximately 0.4 ML/day over a 60 day period The treatment plant bore has a higher transmissivity than the offtake bore and therefore provides a more reliable supply of groundwater. It is also further away from the Betka River and is less likely to impact on surface water values. For these reasons the treatment plant bore is relied upon more heavily than the offtake bore.
2.1.3 Water Treatment Plant The water treatment plant has a capacity of 1.0 ML/day. In the peak periods this capacity is lower than the demand and therefore the treatment plant constrains the system. However, during these peak periods the system is usually also constrained by supply of groundwater to the treatment plant. The bores are generally relied upon to fill the storages in preparation for the peak holiday periods. This results in increased drawdown in the aquifer and reduces the production of groundwater from the bores due to the head losses. The groundwater is high in iron and manganese and is aerated prior to entering the treatment plant to reduce algal blooms from occurring in the raw water storage. From the treatment plant, treated water is delivered to a 240 kL clear water tank for release to customers either directly or via a 23 ML clear water storage at the treatment plant. The clear water storage is covered, however the raw water storage is not, which contributes to system losses through evaporation. A schematic of Mallacoota’s water supply system is shown in Figure 2.
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Figure 2: Mallacoota's Water Supply System
2.2 Allocation of Water 2.2.1 Bulk Water Entitlements EGW has a bulk water entitlement of 330 ML per year for the Betka River. EGW can take up to 1.55 ML per day when flow in the river exceeds 3.1 ML per day or 50% of the flow at other times.
2.2.2 Groundwater Licences EGW currently holds a licence (licence number 9016496) to extract a total of 80 ML of groundwater each year to supplement Mallacoota’s water supply during times of low flow in the Betka River. In August 2008 GHD prepared a hydrogeological assessment for EGW to support an application to access a further 40 ML each year. EGW must comply with a number of conditions, including the submission of a groundwater monitoring program, which provides data for the assessment of potential impacts to surface water features (such as rivers, wetlands and/or groundwater dependant ecosystems) and to the aquifer through saline water intrusion, before Southern Rural Water (SRW) will allow access to the additional water. It is understood that EGW are currently implementing a groundwater monitoring program and investigating a location for a third bore. A review of the last three years of bore level data indicates that 120 ML/year of extraction is likely to be within the sustainable yield of the aquifer. This is consistent with the findings of the 2008 GHD report. The GHD report also concluded that the existing bores have the capacity to supply 120 ML per year to Mallacoota, however there is
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some evidence to suggest that the supply can be affected during peak periods if adequate recharge time isn’t allowed.
2.3 Level of Service Objectives EGW has previously defined the following level of service objectives for water supply reliability: x Moderate restrictions (Stages 1 & 2) are not desired more frequently on average than 1 year in 10 x More severe restrictions (Stages 3 & 4) are not desired more frequently than 1 year in 15.
Further information on allowed uses under each stage of water restrictions is provided at; http://www.egwater.vic.gov.au/DroughtManagement/DroughtMgmtDisplay.htm. Mallacoota is currently subject to Permanent Water Saving Rules, which are being applied as part of a Victoria wide strategy.
2.4 Historical Water Restrictions Historically, there has been difficulty supplying water to Mallacoota in summer. Restrictions were imposed during three drought events, as detailed in Table 2.
Table 2: Summary of Water Restrictions in Mallacoota Drought Event Date Stage of Restriction 1982/83 drought event1 October 1982 Stage 1 January 1983 Stage 2 January 1983 Stage 3 January 1983 Stage 4 May 1983 Restrictions lifted 1987/88 drought event January 1988 Stage 1 January 1988 Stage 3 February 1988 Stage 2 February 1988 Stage 3 March 1988 Stage 3A2 April 1988 Restrictions lifted 1997/98 drought event January 1998 Voluntary restrictions January 1998 Stage 1 February 1998 Stage 2 March 1998 Stage 3 March 1998 Stage 4 May 1998 Stage 2 May 1998 Restrictions lifted 1 The 41 ML storage was not full at the start of the drought event due to maintenance works and the groundwater bores were not commissioned 2 Stage 3A in 1988 was identical to current Stage 4 restrictions, i.e. no external water use permitted
Mallacoota has not experienced water restrictions in recent years.
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3.0 Previous Studies, Legislation and Regulation
3.1 Previous Long Term Planning Studies A number of long term planning reports have been commissioned by EGW (and their predecessors) relating to water supply security. The key documents include: x Drought Response Plan for Mallacoota, SKM (2003) x Water Supply Demand Strategy, SKM (2007) x Licence Increase Application – Groundwater Licence 9016496, GHD (2008)
The reports are summarised in the following sections.
3.1.1 Drought Response Plan for Mallacoota (SKM, 2003) Under section 78B and 78C of the Water Industry Act 1994 all authorities holding a retail water licence are required to develop a Drought Response Plan (DRP) for approval by the Minister. The DRP for Mallacoota aims to provide a framework for ensuring a timely and effective response to water shortages to ensure that social, environmental and economic impacts of shortages are reduced. The DRP included modelling of Mallacoota’s water supply system was used as a basis for the preparation of the initial WSDS in 2007.
3.1.2 EGW Water Supply Demand Strategy (SKM, 2007) The WSDS prepared by SKM in 2007 is EGW’s current WSDS for all of its water supply systems and forms the basis from which this updated WSDS has been developed. The previous WSDS provides long term strategies for managing available urban bulk water supply and customer demand across each of EGW’s water supply systems.
3.1.3 Licence Increase Application – Groundwater Licence 9016496 (GHD, 2008) In 2008, GHD undertook a hydrogeological assessment for EGW to support an application to increase the current groundwater extraction licence by 40 ML per year, to a total allocation of 120 ML per year. The report concluded that the increase would not be expected to have a significant impact on existing groundwater users or surface water features and that a total annual extraction of 120 ML is within the sustainable capacity of the aquifer. The report also stated that the two existing groundwater bores could have the capacity to supply the additional allocation.
3.2 Regulations and Legislation Victoria’s water resources are governed by a number of regulations and legislation. Some key legislation concerning this WSDS are detailed as follows.
3.2.1 Surface Water Caps Each Surface Water Management Area (SWMA) within Victoria is subject to a surface water cap. Any further development in terms of surface water can only be undertaken by trading water rights (via water savings achieved through improvements in distribution and water-use efficiency) or via use of alternative sources of water (e.g. recycled water). Mallacoota does not fall within a SWMA.
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3.2.2 Streamflow Management Plans Streamflow Management Plans (SMP) aim to ensure that surface water is managed in a fair, reliable and equitable manner between both consumers and the environment. They define the rules for sharing water in unregulated rivers and streams and are only developed for priority streams where there are competing water users. There is currently no SMP that applies to the Betka River.
3.2.3 Groundwater Caps Groundwater management in Victoria is undertaken geographically through the identification of a series of areas called Groundwater Management Units (GMU’s). The groundwater management areas in East Gippsland can be seen in Figure 3. The three different groundwater units are: x Groundwater Management Area (GMA) – these cover aquifers with high use of potential for high use to ensure sustainable extraction. Each GMA has been assigned a cap known as ‘Permissible Annual Volume’ (PAV) x Water Supply Protection Area (WSPA) – these cover aquifers that have been identified as having potential value however does not yet require a PAV to be set. Each WSPA has a Groundwater Management Plan to ensure the ongoing protection of the resource x Unincorporated Area (UA) – these cover aquifers where groundwater is expected to provide little potential due to low yields or poor water quality.
Figure 3: Groundwater Management Units in East Gippsland (SKM, 2007)
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Mallacoota is located within an Unincorporated Area therefore no caps on groundwater use have been established.
3.2.4 Regional River Health Strategy Stream value for the Betka River, which supplies Mallacoota, is covered by the East Gippsland Catchment Management Authority Regional River Health Strategy released in 2006. The strategy outlines the value, condition and risks to each waterway. The Betka River is described as having a high value and an excellent condition downstream of the EGW offtake.
3.2.5 Heritage Rivers The Heritage Rivers Act (HRA) identifies a number of Heritage River Areas within Victoria. The HRA prohibits some water-related activities in heritage river areas, including the construction of artificial barriers or structures that may impact on the natural passage of flow. The HRA also restricts and in some cases prohibits the diversion of water, some clearing practices, plantation establishments and domestic animal grazing. The Betka River does not fall under the Heritage River classification and therefore is not subject to any of the above limitations under the HRA.
3.2.6 Victorian River Health Strategy The Victorian River Health Strategy outlines the Government’s long-term policy for managing Victoria’s rivers. It includes a vision for Victorian river management, policy direction on river health issues and a blueprint to integrate all work on Victorian rivers to gain the best river health outcomes (Environment Victoria, 2009). Some of the Legislation that should be considered in the development of any water supply solution includes: x Water Act 1989 x Flora and Fauna Guarantee Act 1988 x Environment Protection Act 1970 x Planning and Environment Act 1987 x Environment Effects Act 1978 x National Parks Act 1975 x Fisheries Act 1995 x Wildlife Act 1975 x Catchment and Land Protection Act 1994 x Environment Protection and Biodiversity Conservation Act 1999
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4.0 Water Demand This Chapter of the report discusses the estimated current water demands in Mallacoota and outlines the likely future demand based on predicted population trends. Best practice water supply planning is to use long term average demands for determining existing per capita water demand. Mallacoota has not been subject to water restrictions in recent years and therefore recent water use data should provide a good representation of unrestricted demand.
4.1 Current Demand Historical water usage data for Mallacoota was obtained from the 2006 Drought Response Plan (DRP) prepared by SKM and is shown in Table 3.
Table 3: Monthly Water Demand (SKM, 2006) Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Total Demand 11.0 11.1 11.4 11.7 12.2 16.5 22.7 14.2 15.5 13.7 11.4 11.0 162.4 (ML) % of 6.8 6.9 7.0 7.2 7.5 10.1 14.0 8.7 9.6 8.5 7.0 6.8 100.0 Annual Demand
Current water usage data was obtained from EGW in the form of bulk water meter data (Table 4) and customer billing records (Table 5).
Table 4: Bulk Water Meter Data Volume (ML) 2006-07 2007-08 2008-09 Betka bore (142799) 22.1 6.9 43.4 Treatment plant bore (142800) 60.7 35.3 46.1 Betka River Offtake 101.8 125.8 62.5 Total Extraction 184.6 168.0 153.0
Table 5: Customer Billing Data 2006-07 2007-08 2008-09 Number of Connections Population1 974 981 988 Residential connections 754 775 Non-residential connections 97 103 Total connections 824 851 878 Total Water Use Residential water use (ML) 107.3 96.4 96.9 Non-residential water (ML) 43.8 52.7 56.4 Total water use (ML) 151.1 149.1 153.3 Per Capita Water Use Litres per household per day 350 343 Litres per person per day2 175 171 1Based on 2006 Census data and EGSC predicted growth rate of 0.7% per annum 2Average household size of 2 as per 2006 census
4.1.1 Unaccounted Water The difference between the readings from the bulk extraction meters, the town supply bulk meter and the customer billings have been compared to determine if any significant losses are occurring in the transfer, treatment and supply networks. The information is shown Table 6.
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Table 6: Unaccounted Water 2006-07 2007-08 2008-09 Transfer and Treatment System Total bulk extraction (ML) 184.6 168.0 153.0 Town bulk water meter (ML) 164.2 159.4 161.6 Change in storage volume (ML) 9.9 -2.3 -13.6 Unaccounted water (ML) 10.5 10.8 5.0 Unaccounted water 6% 6% 3% Reticulation System Total customer billings (ML) 151.1 149.1 153.3 Unaccounted water (ML) 13.1 10.3 8.0 Unaccounted water 8% 6% 5% Total Supply System Unaccounted water (ML) 23.6 21.2 13.3 Unaccounted water 13% 13% 9%
The bulk meter data and customer billing data show total unaccounted water in 2008/09 was approximately 9%, which is a reduction on the two previous years when it was 13%. These losses are consistent with the losses across EGW entire area of service, which was in their 2008/09 Annual Report reported as 8.5% for the 2008/09 financial year. The target set in EGW’s Water Plan is to reduce unaccounted water to 10%. The losses are also typical for a regional water corporation. In comparison, South Gippsland Water reports losses in the order of 10% and Gippsland Water 11% in their 2008/09 Annual Reports.
4.1.2 Non-residential Water Use Non-residential water use accounted for 37% of all water supplied to customers during the 2008-09 billing period. The top five water users in Mallacoota in 2008-09 are all believed to be non-residential users and their water use is shown in Table 7.
Table 7: Top 5 Water Users in Mallacoota Water Use (kL) % of Total 1 15,823 11.8% 2 4,722 3.5% 3 3,213 2.4% 4 1,815 1.4% 5 1,718 1.3%
4.1.3 Summary of Current Demand With no water restrictions in Mallacoota in recent years, it is assumed that the water demand shown in the bulk water meter data represents the unrestricted demand for Mallacoota. It is therefore estimated that the current annual water demand (including non revenue water) for Mallacoota is in the order of 160ML per annum. Monthly demand patterns outlined in 2006 DRP will be used in this study as they are most likely to represent unrestricted demand patterns.
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4.2 Forecast Water Demand To predict future water demand in Mallacoota, the likely trends in population have been reviewed and determined. The following sections provide a review of available information on population in Mallacoota and estimate future water use.
4.2.1 Population Projections in the Previous WSDS Over the period 1991 to 2001, Mallacoota grew at a rate of 0.8% per year while the population in the Orbost Statistical Local Area declined by 0.4% per year (SKM, 2007). Based on this strong historical growth, the previous WSDS (SKM, 2007) assumed that Mallacoota would continue to grow at a higher rate than surrounding areas.
4.2.2 Census Data Since the previous WSDS (SKM, 2007), the 2006 census data has been released. The 2006 census data provides population details based on the usual place of residence, which indicated that the permanent population in Mallacoota was 974 people. Population details based on usual place of residence in Mallacoota are not available from the 2001 census. To allow comparison of the 2001 and 2006 data, the number of people counted in Mallacoota on census night, who usually live there, are compared in Table 8. The data does not account for residents of Mallacoota who were absent on census night.
Table 8: Census Data (2001 and 2006) Year Persons Counted Occupied at Home Dwellings 2001 912 462 2006 834 422
This comparison shows a 9% decline in the number of people counted in Mallacoota between 2001 and 2006. This equates to an average annual decrease of 1.8%. This is inconsistent with the growth experienced in Mallacoota in the decade prior to 2001 (SKM, 2007). This comparison may not provide an accurate indication of the population trends occurring in Mallacoota between the 2001 and 2006 census nights, as it does not capture residents of Mallacoota that were absent on census night.
4.2.3 Victoria in Future Data The smallest regional breakdown of data available from Victoria in Future is for the Orbost Statistical Local Area (SLA). Available 2008 projections for the Orbost SLA suggest an average annual increase of 0.4% to 2026. Historical population growth in Mallacoota shows that it is growing at a faster rate than the surrounding SLA.
4.2.4 East Gippsland Shire Council An Urban Design Framework for Mallacoota was prepared for East Gippsland Shire Council in 2007. The Framework provides strategic guidance for the future development of Mallacoota and provides the following information relating to future population growth: x Mallacoota is likely to grow strongly and age significantly over the next 30 years as many retirees move to Mallacoota x The projected average annual rate of population increase in East Gippsland is 0.32% x Over the past 15 years Mallacoota has been growing at 2.2 times higher than the East Gippsland average.
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4.3 Summary of Demand Projections Based on the information presented above, it is likely that the population in Mallacoota will continue to grow into the future, however the rate at which this growth may occur is uncertain. To account for uncertainties in future growth rates, two alternative scenarios will be modelled: x Alternative 1 – Continued population growth (and hence demand) at 2.2 times the average annual growth predicted for East Gippsland (i.e. 0.7% per annum increase). This is considered to provide a worst case scenario consistent with EGSC’s Urban Design Framework for Mallacoota. x Alternative 2 – Population growth (and hence demand) consistent with the average annual growth predicted for East Gippsland (i.e. 0.32% per annum increase), providing a best case scenario.
The two demand alternatives are shown graphically in Figure 4.
Figure 4: Demand Projections
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5.0 Demand Management
5.1 Measures to Achieve Demand Reduction Targets The 2007 WSDS detailed both current (at 2007) and future demand reduction initiatives for EGW’s service area. There have been no significant changes since then and as such the majority of this text has remained the same. Sections 5.1.1 and 5.1.2 of this report are direct excerpts from the 2007 WSDS (SKM) with updates provided in italics.
5.1.1 Current Demand Reduction Initiatives (SKM, 2007) East Gippsland Water is currently undertaking measures which are expected to result in per capita demand reduction over time. EGW is part of the savewater!TM alliance through the Victorian Water Industry Association, which represents all of Victoria’s water authorities. Details of the savewater! TM initiative can be found at http://www.savewater.com.au. The site provides information on water conservation, runs competitions to win water conserving products and provides access to suppliers of water conserving products. For estimating the effect of demand reduction initiatives, East Gippsland Water relies upon the detailed demand information derived from Melbourne’s end-use model, which models property scale demand by considering the in- house and external water use of each property (WaterSmart, 2006a). It is acknowledged that there are some differences between consumer behaviour in Melbourne and East Gippsland, however given the high degree of uncertainty surrounding demand reduction forecasts, this adoption of technical information from Melbourne with justifiable adjustments is considered appropriate. In recent years, water conservation efforts by the water utilities and the Victorian Government have targeted all major aspects of residential water use with an emphasis on education and behaviour change. A rebate scheme for water conservation products has been operating since January 2003. For example, AAA shower roses attract a $10 rebate on the purchase price, whilst rainwater tanks with a connection to the toilet for flushing attract a $300 rebate. The most noteworthy regulatory changes affecting residential indoor water use have been: x The introduction of a mandatory water efficiency labelling for appliances (commencing 2006) under the national Water Efficiency Labelling and Standards Scheme (WELS); x The introduction of rising block tariffs, which result in higher charges for high water users; and x The Five Star Home standards which require all new homes in Victoria to have water efficient showerheads, tapware, a pressure reducing valve where mains pressure is over 50 m, and either a solar hot water heater or a rainwater tank connected to the toilet (or equivalent saving through a dual pipe system).
Outdoor water use has been targeted through the introduction of permanent water saving measures, which include the requirement for a trigger nozzle on hoses, restricted times for garden watering, no hosing of paved areas and notification to be given to East Gippsland Water when filling a new pool. These State wide measures are expected to result in a 2% reduction in total demand (TWGWSA, 2005). A per capita demand reduction of 22% has been achieved in Melbourne over the last decade, however some of this demand reduction is due to recent water restrictions and hence it is unclear whether all of this demand reduction will be maintained when restrictions are lifted (Watersmart,2006b). This reduction includes water savings by industry, government and households. WaterSmart attributes this to water conservation programs, water pricing reform, water audits with major industrial water users, the five star building standard, permanent water saving measures, water saving garden centres, savewater.com alliance, leak control programs and the national water efficiency labelling scheme. Of these activities, East Gippsland Water has only just introduced permanent water saving measures, well after they were introduced in Melbourne, which are expected to result in a 2% reduction in demand (TWGWSA, 2005). This is effective from 2005/06 onwards. EGW also has an active leakage detection program which has completed works in Dinner Plain, Orbost, Cann River, Metung, Paynesville & Eagle Point. These are areas where East Gippsland Water believes that high rates of leakage may occur.
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It could be argued that household disposable income, water authority revenue and access to information are lower in regional areas than in Melbourne, so the water savings due to other activities could be expected to lag those achieved in Melbourne. Quantifying this lag is difficult, hence it has been conservatively assumed that existing demand reduction measures will merely serve to maintain existing per capita demand, similar to what has been assumed in Melbourne, apart from the initial 2% reduction in demand due to the introduction of permanent water saving measures. This assumption has been carried forward into this updated WSDS for Mallacoota. Estimating per capita demands in East Gippsland is problematic because of the difficulty in accurately assessing the population being serviced. The estimate of population from census information is only collected in winter and therefore significantly underestimates peak summer and Easter populations, which swell due to an influx of tourists to the region. Monthly demand patterns outlined in 2006 DRP will be used in this study as they are most likely to represent unrestricted demand patterns. The unrestricted annual demand will be broken down by month based on this demand pattern. Estimating a change in per capita demand is equally problematic without knowledge of changes in seasonally weighted populations. This is because a change in winter population does not necessarily translate directly into a linear change in summer population, which is affected by the state economy (influencing disposable income and therefore travel decisions), weather conditions and accommodation capacity.
5.1.2 Future Demand Reduction Initiatives (SKM, 2007) East Gippsland Water will actively pursue demand reduction in each supply system. East Gippsland Water has set itself a demand reduction target in line with State Government targets set for other water authorities across Victoria of: x A 25% reduction in per capita demand by the year 2015 relative to 1990s average demand; and x A 30% reduction in per capita demand by the year 2020 relative to 1990s average demand.
Assuming that the 22% reduction in per capita demand has already been achieved in East Gippsland, East Gippsland Water would require a 3% reduction in per capita demand from its customers by the year 2015 and an 8% reduction in per capita demand by the year 2020 in order to reach this target. This includes the 2% reduction in demand due to the recent introduction of permanent water saving measures that is not likely to have been realised relative to the 2005/06 demand data used in this strategy. A range of actions by East Gippsland Water and the State Government will be required to meet these targets. It is anticipated that the majority of these actions would be driven by the State Government and Melbourne’s urban water utilities. Specific actions by East Gippsland Water include the following: x East Gippsland Water will continue to work with its major customers to reduce the water use of those major customers. x East Gippsland Water will continue its leak reduction program. x East Gippsland Water will continue to keep abreast of technological developments in water saving measures currently being investigated by Melbourne’s urban water utilities through East Gippsland Water’s membership of the Victorian Water Industry Association.
Specific actions by other organisations that will contribute to East Gippsland Water’s customers achieving the demand reduction target are as follows, as outlined in the Central Region Sustainable Water Strategy: x The State Government will extend its existing water savings behavioural change program until 2015. – This program is still running x The State Government will by 2006/07 introduce on-the-spot fines for breaching water restrictions or the permanent water saving measures – This has been adopted x The State Government will reform the water component of the 5-star building standard to make it performance based. This is expected to be operational by 2009
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x The State Government will by 2010 seek the adoption of standards under the national Water Efficiency Labelling Scheme for water appliances to set mandatory minimum or higher than existing standards for showerheads, washing machines, toilets and evaporative coolers x The State Government will consider the rollout of smart water meters showing real time water use after completion of a trial in south east Melbourne by December 2007 – Trials completed and smart water meters were provided to Melbourne’s top 200 industrial water users. During 2007 the Victorian Government advised that Smart Water meters will be rolled out to all customers using 10 million litres or more of water per year. The progress of this rollout is unknown. x The Water Smart Homes and Gardens Rebates scheme, currently funded by the Victorian Water Trust, will be extended for a further four years until June 2011. This scheme makes rebates available for water tanks, dual flush toilets, greywater systems and other water saving appliances and devices – Scheme is still active x The State Government will develop a web-based ready reckoner to assist home owners in choosing different water saving options for their home by 2007 – This action has been completed x The State Government will continue until 2009 the Sustainable Water Efficiency Program for schools. This involves an audit of indoor water use and a retrofit of fittings and appliances – This program is still running
The extent to which demand reduction targets are achievable in any given year will be influenced by the age profile of assets, particularly in small supply systems, of which East Gippsland Water operates several. As assets such as pipelines approach the end of their useful life, they will leak or burst, increasing water losses. Measuring the effectiveness of these actions against East Gippsland Water’s target will be based on measuring the change in the per capita demand from the current 335 litres per capita per day to 325 litres per capita per day by 2015 and 310 litres per capita per day by 2020. These targets are based on an assumed seasonally weighted population of double the winter population. Meeting these targets also assumes that the seasonally weighted population increases in proportion to the increase in winter population for the period over which the targets have been set.
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6.0 Water Supply
6.1 Future Reliability of Surface Water 6.1.1 Impact of Climate Change The greatest concern for Mallacoota’s water supply system relating to climate change is a significant reduction in the volume of surface water available for extraction from the Betka River. A report titled “Future Runoff Projections (~2030) for South East Australia” by the South Eastern Australian Climate Initiative (SEACI) (2008) was used as the basis for obtaining stream flow reduction figures. The methodology used in this paper is similar to the paper “Rainfall-runoff modelling across the Murray-Darling Basin” (CSIRO 2008), which was used to source stream flow reduction figures for the Omeo WSDS, but uses a medium emissions scenario only to formulate runoff scenarios. Mallacoota is not covered by the study area of either report but is close to the boundary of the SEACI region; changes in runoff have therefore been sourced from the latter report. The percentage change in modelled mean annual run off for Mallacoota (~2030 relative to 1990) is projected to be -5% for the median scenario and -10.8% for the dry scenario (pers. comm. David Post). The CSIRO report states that: “Almost all the catchments available for model calibration are in the higher runoff areas in the southern and eastern parts of the SEACI region. Runoff estimates are therefore generally good in the southern and eastern parts of the SEACI region but comparatively poor elsewhere.” Mallacoota is located close to the south eastern corner of the MDB and so the figures derived in the report are assumed to be applicable to that catchment. The dry scenario has been selected as the most prudent scenario (i.e. a -10.8% change in mean annual runoff) upon which to plan future water supply given the Gippsland Region Sustainable Water Strategy: Discussion Paper (2009) notes that the low inflows experienced since 1997 may represent a permanent step change in reservoir inflows. More comprehensive information regarding the potential impacts of climate change on water supply is scheduled to become available in the first half of 2010, including: x Finalisation of the Gippsland Region Sustainable Water Strategy – this is expected to provide guidance regarding considering potential impacts of future climate change for the purpose of water supply planning x SEACI modelling for the high emissions scenario published: current climate projections are only available for the medium emissions scenario for the SEACI region, which includes the majority of EGW’s supply area. Based on recent climate change science (e.g. Rahmstorf 2007), we are currently tracking at or above worst case scenarios for emissions and temperature, and it is therefore prudent to plan based on a high emissions scenario.
For the purposes of this report the published results from SEACI report have been adopted, however EGW should consider reviewing these assumptions in 2010 when the additional data is released.
6.1.2 Step Change It is possible that the low inflows that have been experienced since 1997 represent a permanent step change. SEACI will be conducting research over the next three years to investigate the reasons for the recent dry conditions and determine the suitability of the various global climate models for south eastern Australia. It may take decades before it is understood if the inflows of the past 12 years are part of the normal cycle of climate variability or if a permanent step change has been experienced. As such, it is important to ensure that water supply planning takes this possibility into consideration. Streamflow gauging has only occurred intermittently on the Betka River and does not provide enough data to compare actual flows pre and post-1997. As an alternative, modelled streamflows produced by the rainfall-runoff
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model developed by SKM for the 2007 WSDS have been used. The model may actually overestimate some of the larger streamflow events and therefore using the modelled flows provides a conservative estimate of average reduction in streamflow. The modelled flows show that the reduction in average flows pre and post-1997 is 31%. Using continued low flows therefore represents a greater impact on water supply in Mallacoota than the dry climate change scenario.
6.1.3 Impact of Bushfires Bushfires in forested catchments have the potential to significantly impact runoff and therefore streamflows over time. Runoff after bushfires initially increases in the first few years until vegetation starts to re-grow, when runoff starts to decrease. The maximum reduction in runoff generally occurs approximately 10-30 years after the fire, before increasing back to pre-fire levels. The Betka River catchment is predominately forested with mixed species of eucalypt trees, the most common being E. Sieberi or Silvertop. The response of catchments to bushfires varies with different vegetation types. This relationship between stream runoff and recovery for different species is shown in Figure 5.
Figure 5: Estimated reduction in streamflow due to bushfire (Hill et al, 2008)
Previous Bushfire Events The most recent bushfire affecting the Betka River catchment was in January 1983, when approximately 95% of the catchment was burnt. The curve shown in Figure 5 has been used as a guide to understand the impact that the 1983 forest fire may be having on the current Betka River catchment runoff. The curve shows that the greatest reduction in runoff is expected to occur between 20 and 30 years after the bushfire. A severe drought event was experienced in Mallacoota in 1997/98, which was approximately 15 years after the catchment was burnt. It is now 27 years after the bushfire and runoff is expected to begin returning back towards historical levels (dependant on climatic changes) as the catchment continues to regenerate.
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Discussions with DSE have provided an appreciation for the complexity of the interactions between climate change and the impacts associated with bushfires. DSE has given preliminary advice that a drier climate could reduce the percentage impact of bushfires on streamflows however there is currently no published literature to support this theory. To take a conservative approach, no increase in streamflow resulting from bushfire impacts will be considered in the WSDS. This approach is consistent with advice from DSE.
Proposed Fuel Reduction DSE is proposing to undertake fuel reduction burns over the next 3 years that will impact on 36% of the Betka River catchment. It is proposed to burn a further 1% of the catchment in 2011. It is estimated that 12% of the proposed burns are located in the higher yielding portion of the catchment and EGW has requested that DSE commit to re-burning this area within the next 15 years. EGW has also requested that the fuel reduction will be done by “cool” burning and will have a far lesser impact on runoff than a bushfire. Discussions with DSE have confirmed that runoff impacts from fuel reduction burning will be minor and do not need to be considered in the WSDS.
6.1.4 Forestry Areas within the Betka River catchment are logged on a rotation basis. Similar to the impacts of bushfires, logging reduces streamflows in the long term as the forests re-establish. The previous WSDS concluded that the impact of this logging on the offtake would be relatively small, provided the logging remains dispersed across the catchment (SKM, 2007). Any increase in logging area will have a detrimental impact on streamflow. Continued logging will impact upon the streamflow within the Betka River. To improve water supply reliability, it is recommended that EGW continue to seek a reduction in the area to be logged within Mallacoota’s water supply catchment.
6.2 Future Reliability of Groundwater To assess the likely future reliability of groundwater, the last 3 years of groundwater level data in the two extraction bores has been reviewed. The analysis has been based on a total annual extraction of 120 ML. While the current extraction volume for Groundwater License number 9016496 is 80 ML per year, it is possible that the license will be increased pending further investigations by EGW. A detailed summary of the analysis is provided in Appendix A.
6.2.1 Long Term Reliability and Climate Change Similar to surface water supplies, groundwater is also susceptible to climate change and increasingly drier conditions may result in a significant reduction in the volume of water available for extraction. To consider the effect that climate change may have on the availability of groundwater, the decreases in rainfall associated with a dry climate change scenario was assessed. Under the dry scenario there is expected to be a 10% reduction in historical rainfall levels by 2030. Using a recharge rate of 5% (GHD, 2008) and an estimated total area of exposed bedrock aquifer of 15.2 km2 (GHD, 2008), the estimated annual volume of recharge available over the area is calculated to be 569 ML. It should be noted that it is possible that the rate of recharge will decrease if the climate becomes drier. If the total allocation of groundwater extraction is 120 ML for Groundwater License 9016496 and 2 ML is allocated for other Stock and Domestic used in the region (122 ML total allocation), this would represent less than 22% of the annual recharge estimate for the catchment. It is therefore considered that, given a 10% reduction in rainfall due to climate change, the current allocation to 120 ML/yr is well within the sustainable yield of the aquifer even under conditions of lower rainfall.
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However, over the three year period both wells show an overall trend of decreasing water levels (around a 3 - 5 m), EGW should undertake further monitoring to verify whether this is indicative of a long term trend for the entire aquifer.
6.2.2 Short Term Reliability Water level data for the two extraction bores over the period October 2006 to November 2009 shows fluctuating levels generally corresponding to daily extraction rates. The data shows a relatively quick recovery following each water extraction event, indicating water available in storage. The recent problems experienced by EGW operators are expected to be localised caused by over pumping of the existing wells. Additional wells located outside of the sphere of influence of the existing wells, would allow more time for recharge during high extraction events. Water level data suggests that the wells are in good condition and that the water allocation of 120 ML is well within the sustainable yield of the aquifer and that the existing bores should be capable of extracting this volume. Given that the Mallacoota Treatment Plant Bore (142800) has a higher transmissivity than the Betka bore (142799), this well is expected to be the most reliable groundwater supply bore of the two and contribute the greater volume of groundwater to the overall water allocation.
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7.0 Reliability of Supply The storage reservoirs at Mallacoota operate as “within year” reservoirs fed from an unregulated stream (Betka River). Unlike “carry over” reservoirs on larger supply systems, “within year” reservoir’s refill on an annual basis and are designed to drawdown over a shorter period typically of a month or two of low flows. The critical period for Mallacoota’s reservoir occurs during summer and drawdown can occur quite rapidly when the Betka River is often not flowing. Behavioural simulation analysis using a REALM model was used to assess the likely performance of the water supply system under different future supply and demand conditions. The methodology and assumptions for the modelling are outlined in Appendix B.
7.1 Current Reliability of Supply The existing water supply system was modelled to assess its reliability with regards to EGW’s level of service (LOS) objectives. The analysis was conducted using a REALM model with the main inputs being current annual demand of 160 ML and a continuation of the low flows experienced since 1997 (31% reduction to average pre- 1997 flows). The model shows that (see Figure 7) with the changed climatic conditions, water restrictions would not be required. This is achieved through a reliance on groundwater. The groundwater extraction over the modelled period is shown in Figure 8, which shows that the groundwater extraction would not exceed the proposed new license conditions of 120 ML. Mallacoota has been subject to restrictions in the past (refer to Section 2.4), which differs from the results of the REALM modelling. However these restrictions occurred prior to 2000 when the capacity of the groundwater pumps was upgraded.
7.1.1 Model Limitations The model does not take into account the level of drawdown being experienced in the aquifer at any one time and treats groundwater as a constant supply, regardless of drawdown. The results of the model are only valid if the bores can deliver the licensed volume of groundwater when the river is not flowing. Discussions with EGW operators at the Mallacoota depot, suggest that the increased reliance on groundwater is not allowing sufficient time for the aquifer to recover and drawdown from the existing bores is reaching maximum limits. The model was therefore run assuming a long term continuous supply of 0.4 ML/day which was the average production capacity observed during the recent extended dry period of January – July 2009. In addition, to the uncertainties surrounding the groundwater, there is only a limited amount of gauged stream flow data to base the modelling on. The majority of the stream flow data was simulated using the rainfall-run off model, as show in Figure 6.
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Figure 6: Modelled and Gauged Flow in the Betka River
7.1.2 Sensitivity to Groundwater Supply Capacity Given the reliance of these results have on groundwater capacity, a sensitivity analysis was performed to assess the impact of an extended reduction in groundwater supply. This could occur due to declining groundwater levels or an extended operational failure from one of the bores. A decreased rate of continuous groundwater extraction of 0.2 ML/day was used which could occur if the Betka bore was the only operable bore for a period of multiple months. The results shown in Figure 7 show that a reduction in supply of 0.2 ML/day would significantly increase the storage drawdown during dry periods. Although EGW would still be able to meet the target LOS objectives, the sensitivity analysis demonstrates the importance of a reliable groundwater supply.
7.1.3 Setting Restriction Triggers Reliability of supply is significantly impacted by the setting of restriction trigger levels and the demand reductions associated with these restriction levels. Restriction trigger levels need be set in consideration of: x The desired frequency of restrictions (defined by EGW’s LOS objectives) x Allowing sufficient time between restriction levels for community adjustment x Allowing sufficient time for EGW to arrange emergency supply arrangements in the rare event of reservoir failure The restriction triggers, set by EGW in Mallacoota’s 2006 DRP are shown in Table 9.
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Table 9: Restriction Triggers Start of Month Stage of Restriction (Triggered by dropping below listed storage volumes – given in ML) Voluntary One Two Three Four Jan 17.8 16.8 14.6 12.7 10.3 Feb 9.0 9.0 9.0 9.0 9.0 Mar 9.8 9.0 9.0 9.0 9.0 Apr 9.0 9.0 9.0 9.0 9.0 May 9.0 9.0 9.0 9.0 9.0 Jun 9.0 9.0 9.0 9.0 9.0 Jul 9.0 9.0 9.0 9.0 9.0 Aug 9.0 9.0 9.0 9.0 9.0 Sep 9.0 9.0 9.0 9.0 9.0 Oct 9.0 9.0 9.0 9.0 9.0 Nov 14.1 10.2 9.0 9.0 9.0 Dec 19.0 16.2 12.8 9.0 9.0
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Figure 7: Reservoir drawdown under current operating conditions
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Figure 8: Groundwater extraction under current operating conditions
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Figure 9: Reservoir drawdown under current operating conditions
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7.2 Future Reliability of Supply To account for the uncertainty associated with climate change and population growth, two scenarios were created to assess Mallacoota’s future reliability of supply. Increase in runoff resulting from the 1983 bushfires has not been considered as discussed in Section 6.1.3.
Scenario S1 – High Impact This scenario presents the worst case future water supply situation and combines the most dire of predicted outcomes for each of the following variables: x Continuation of low flows experienced since 1997 (31% reduction to pre-1997 flows) x High population growth (0.8%)
Scenario S2 – Moderate Impact This scenario presents the best case future water supply situation and combines the best predicted outcome for each of the main variables: x Medium climate change scenario (5% reduction) x Medium population growth (0.32%)
Table 10: Summary of REALM Modelling Scenarios Scenario Reduction in Increase in Population growth Streamflow from Streamflow from Climate Change Bushfires S1 – High Impact 31% 0% 0.8% S2 – Moderate Impact 5% 0% 0.32%
7.2.1 Summary of Future Reliability of Supply The REALM modelling indicates that under a repeat of historical climatic conditions, the Mallacoota water supply system has sufficient reliability to enable EGW to meet its level of service objectives for the next 50 years even under a High Impact Scenario (continuation of lows flows, high population growth). These results are dependant on the short term and long term reliability of groundwater supply as discussed below. The detailed results are contained presented in Tables 11 and 12 below. Although the level of storage drawdown is expected to increase dramatically with increased future demand, EGW would still be able to meet its level of service objectives if the current restriction triggers are maintained. Under the Moderate Impact Scenario the level of drawdown is less severe refer to Appendix C for details.
Short–term Reliability of Groundwater The results of the model are only valid if the bores can deliver the modelled volume of groundwater when the river is not flowing. As discussed earlier in this report, the increased reliance on groundwater is not allowing sufficient time for the aquifer to recover locally and drawdown is reaching maximum limits. To test the sensitivity of the model, the high impact scenario has been modelled using a decreased rate of groundwater extraction. As with the current demand scenario the model was run assuming a reduced long term continuous supply of 0.2 ML/day which matched the average observed production from the Betka bore during the recent extended dry period of January – July 2009. The results are shown below in Table 13 and indicate that with a reduction in groundwater supply capacity the storage could fail twice in 100 years and approach failure on a number of additional occasions. This again highlights the importance of a reliable groundwater supply in ensuring the township has a reliable water supply.
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Long-term Reliability of Groundwater It has been assumed that the full volume of groundwater licensed for extraction (120 ML/year) will be available throughout the 50 year planning horizon. A review of the groundwater data (refer to Appendix A) suggests that an extraction volume of 120 ML/year is within the sustainable yield of the aquifer. However, there has been a noted decline in groundwater levels over the last 3 years. In addition, the recharge rate of the aquifer may also be reduced in the future as a result of predicted climate change impacts. As part of EGW’s requirements under the revised licence, groundwater levels will be monitored to ensure there is no long term decline in groundwater levels or water quality across the aquifer. If this monitoring indicates such an occurrence, this model should be updated to determine the impact on the systems reliability of supply. As there is considerable uncertainty around the long-term reliability of the groundwater, alternative water sources have been identified with the objective of providing a back up supply should groundwater cease to provide a reliable supply at some point in the future.
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Table 11: Future Reliability of Supply – High Impact Scenario
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Table 12: Future Groundwater Extraction – High Impact Scenario
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Table 13: Future Surface Water Extraction – High Impact Scenario
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Table 14: Future Reliability of Supply with Reduced Groundwater Extraction
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8.0 Alternative Water Supply Options The results of the modelling presented in Chapter 7.0 of this report showed that Mallacoota currently has a secure water supply. However, future growth in demand will increase the town’s already heavy reliance on existing groundwater supplies, which have been experiencing diminished reliability in recent years. This section of the report discusses alternative water supply and demand management options that could improve the system’s reliability of supply and reduce the risk of EGW not being able to meet their LOS objectives.
8.1 Surface Water 8.1.1 Qualification of Rights on the Betka River There is unlikely to be any benefit in applying for a Ministerial Qualification of Rights to gain access to the environment’s share of the river flow in the Betka. Streamflow records show that the river recedes relatively quickly in dry periods and ceases to flow on a regular basis, providing no benefit for Mallacoota. The previous drought response plan (SKM, 2003) identified pumping from deep pools on the Betka as a potential source of water during dry periods. While it may be possible to pump from these pools for emergency supply, this option has a number of constraints and issues, including: x It will put further stress on aquatic environments during times of low flow x Potential volume and quality are unknown x Difficult to access x Difficult to get temporary infrastructure to extract and transport the water from these deep pools.
Accessing additional water from deep pools on the Betka River may be possible during times of emergency. For the reasons discussed above, it should only be considered as a last resort and other options for emergency supply should be investigated in preference. For these reasons this option has not been considered further in this WSDS.
8.1.2 Water Trading There are no other users on the Betka River and therefore no opportunity to transfer or exchange bulk entitlements.
8.1.3 The Genoa River There may be the potential to supply Mallacoota with surface water from either the Genoa River or the Wallagaraugh River. The two rivers meet upstream of Gipsy Point. Gipsy Point, located in the upper reaches of the Mallacoota Inlet, is the closest point to Mallacoota that would provide access to surface water. It is likely that surface water at this location is brackish, however there is no available data to confirm this. It is likely that water would need to be extracted further upstream from Gipsy Point. Genoa is likely to be the closest location, which is approximately 20 km from Mallacoota. Gauging records are available for the Genoa River at The Gorge from August 1972 to current. Review of the stream flow data shows that: x The river ran dry 9 times during the record x There were 6 events where the Genoa River ran dry for more than 30 consecutive days x Of these 6 no-flow events, 4 occurred within the last decade x There were no-flow events of over 100 consecutive days experienced in 2006 and 2009 x The river was dry from beginning of March to end of June 2009
A comparison of the gauged flow in the Genoa River and the flow in the Betka River recorded by EGW operations staff over the last 3 years is shown in Figure 10. The Genoa River catchment is larger than the Betka and
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therefore produces more streamflow. However, as Figure 10 shows, the Genoa runs dry at similar times to the Betka, although for generally shorter periods. The Genoa is likely to provide a greater volume of water than the Betka, but will still have issues with reliability during dry periods.
Figure 10: Streamflow Comparison - Betka and Genoa Rivers
There is no available streamflow data for the Wallagaraugh River. The option of extracting water from the Genoa River has not been considered further due to the length of pipeline (i.e. ~20km) required to connect these sources to the existing supply system. 8.1.4 Brackish Water or Seawater Brackish (slightly saline water) or seawater could be sourced from coastal waters near Mallacoota and treated using reverse osmosis to reduce the salt content to acceptable levels. There are a number of barriers to implementing a desalination scheme, including: x Finding a suitable harvesting location x Environmental impacts, such as salt intrusion, impacts of brine discharge x Disposal of the brine waste stream x Energy consumption – treatment of brackish and saline water using reverse osmosis is energy intensive
In this case EGW currently has a brine discharge licence for the abalone co-op in Mallacoota and it may be possible to utilise this existing discharge licence making the approval process for a desalination project more straightforward. However it is unlikely that approval from regulatory agencies would be easy to obtain due to the other issues discussed above. A desalination scheme may be more suitable as an emergency supply option, where EGW purchases a mobile desalination plant that can provide water to Mallacoota as well as other towns in East Gippsland during critical dry periods. It could also be rented out to other water corporations when it is not being used by EGW. The investigation of this option should be undertaken following completion of the remainder of EGW’s WSDS’s.
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8.2 Groundwater The two groundwater bores at Mallacoota have become an integral part of the town’s water supply over the past few years, as flows in the Betka River have become less reliable. Operational difficulties at the treatment plant were experienced when groundwater initially became a large part of supply. This was due to the high levels of iron and manganese leading to algal blooms in the raw water storage. The operational difficulties have now been overcome with aeration being introduced prior to the raw water storage. EGW will be granted a licence increase to 120 ML per year once a groundwater monitoring program has been deployed. Review of available groundwater level information for the last 3 years and the licence application report (GHD, 2008) shows that 120 ML/year is within the sustainable yield of the aquifer. The GHD report also concluded that the existing bores and pumps should be capable of delivering this volume of water. The bore at the treatment plant has a higher transmissivity than the Betka bore and is relied on more. As a result, the treatment plant bore has been drawn down to the screens in the past.
8.2.1 Additional Groundwater Bores Whilst current extraction appears to be well within the sustainable yield of the aquifer, the recent increased reliance on groundwater has resulted in a localised decline in aquifer recharge in the vicinity of the existing bores. To allow the treatment plant bore to adequately recharge another bore or bores could be installed to take the pressure off the existing bores. EGW is currently undertaking an investigation to identify suitable locations for additional groundwater bores. The investigation should determine how many additional groundwater bores are required to supply Mallacoota’s peak monthly demand over the planning horizon. This option continues the transition of Mallacoota’s water supply from a predominantly surface water supplied system to a predominantly groundwater supplied system. Given the uncertainty regarding the Betka River’s long term reliability, EGW should consider applying to have their groundwater licence increased further beyond the currently proposed 120 ML/yr. Indications are that an increase of 100 ML/yr (enough to meet all of the system’s projected long term demand) would be within the sustainable yield of the aquifer. This would need to be verified by monitoring.
8.2.2 Managed Aquifer Recharge Managed Aquifer Recharge (MAR) is the controlled recharge of an aquifer with a water source, such as surface water or recycled water, for storage and later beneficial use. MAR offers advantages such as additional natural treatment and storage to buffer seasonal variations in water supply. MAR would only be required if groundwater levels continue to decline across the whole aquifer or if saline intrusion is detected during long term monitoring of the aquifer. In this instance there may be the opportunity to use the aquifer as storage and improve the long term reliability of the aquifer. Surface water from the Betka River could be injected into the aquifer when the raw water storage is full or when the Betka bore is in use and the pipeline is already in use. MAR is not suggested as a solution to localised draw down More investigation would be required to verify the technical feasibility of this option and EGW should investigate whether any efficiencies could be gained by combining some initial feasibility investigations with the other groundwater investigations currently being undertaken at Mallacoota.
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8.3 Demand Management Analysis of water meter data has shown that the top five water users in Mallacoota use over 20% of the total supply.
8.3.1 Auditing High Water Users There is likely to be some opportunities for water savings by reducing demand of the top water users, whether it is through the installation of water efficient devices such as shower heads, potable substitution with rainwater or other water sources, leakage detection and education awareness programs. It is difficult to quantify the savings associated with reducing demand from the top water users and as such it is suggested that EGW undertake a water audit of the top water users to determine the feasibility of these water savings. It is expected that targeting high water users will be more effective than targeting the general customer base, where significant savings are unlikely due to the influx of holiday makers during peak periods.
8.3.2 Foreshore Caravan Park The Foreshore Caravan Park uses a significant portion of the water supplied to Mallacoota due to the large influx of holiday visitors that they receive each year. The caravan park has been working to reduce their water consumption by retrofitting their amenities with water efficient devices. In addition, EGW installed a pressure reducing valve (PRV) to try and reduce consumption by limiting the pressure. The PRV is being installed prior to the peak summer period of 2009/10 and billing data should be reviewed in 2010 to determine what savings were made as a result and if further savings should be pursued. Discussions with the Caravan Park management indicate that main water uses at the caravan park are: x Toilets and showers x Laundry x Washing boat engines x Vehicle washing (with a bucket only)
There is no irrigation of open space, such as camping lots or gardens, as they have traditionally had enough rainfall. They also use water saving shower heads and have dual flush toilets and have a maintenance supervisor who actively monitors water use, including fixing leaking taps.
Alternative Water Supply There may be some opportunity for reducing water consumption, however given that they already have water efficient devices installed and don’t irrigate open space, there is likely to be more opportunity to supply an alternative source to reduce reliance on the potable supply. Feasible alternative sources include: x Raw groundwater – installation of a groundwater bore at the caravan park to supply non-potable uses. End uses will be dependent on quality of the groundwater. x Rainwater – rainwater harvested on site for non-potable uses. Reliability dependent on adequate roof area. x Recycled water – supplied from the wastewater treatment plant for toilet flushing. This would require the installation of a pipeline and an upgrade of the treatment plant to provide Class A water.
Supplying recycled water to the caravan park will require an upgrade to the treatment plant to achieve Class A quality. The Class A water could then be used for toilet flushing and outdoor uses. Given that the caravan park does not have significant outdoor uses, supplying recycled water is not likely to be a cost effective option. Supplying either groundwater or rainwater, depending on quality, is likely to have more end uses at the caravan park than recycled water such as showers and laundry. It is also likely that supplying groundwater or rainwater would be less expensive than supplying recycled water. For these reasons the option of supplying groundwater or rainwater or a combination of the two has been considered further.
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Changing Water Use Behaviour In the past, the managers of the caravan park have installed signage to educate their visitors on the importance of conserving water and ways in which water consumption can be reduced. However, this material was not focussed specifically at caravan parks. EGW should ensure that the managers of the caravan park are supplied with up to date signage and educational material to help in improve water use behaviours amongst holiday visitors.
8.4 Improve System Performance 8.4.1 Water Loss Reduction When comparing the water meter readings for the 2008-09 financial year (in Table 5) and the bulk water meter readings for the same period (Table 4) it can be seen that approximately 13 ML of water is unaccounted for between the off-takes and customers meters. Some of this water is used by EGW for operational purposes, whilst some of this water is likely to be lost as evaporation from the raw water storage and from system leakage. It is likely that a significant proportion of the lost water can be attributed to evaporation from the raw water storage. With an approximate surface area of 1.2 Ha and a recorded evaporation of 926 mm in 2008-09, approximately 10 ML of water would have been lost as a result of evaporation in 2008-09. EGW currently have a grant application pending to cover the raw water storage but as this has not happened yet it will be considered further as an option. Comparison of the bulk meter at the outlet of the treatment plant and the water meter reading shows that approximately 5 ML or 5% of water is unaccounted for in the distribution network. Water systems typically operate with up to 10% unaccounted for water and reducing losses further in an already efficient system is unlikely to be cost effective in comparison with alternative options to improve reliability of supply. It is however, recommended that EGW continue to monitor losses in the distribution system to ensure they do not increase and as infrastructure ages and requires replacement, EGW should ensure that the reticulation network is replaced with appropriate pipe materials to further reduce leakage.
8.4.2 Increase Storage Mallacoota currently has 64 ML of storage capacity in the supply system. This equates to approximately 38% of the annual supply. Additional surface water storage requires significant capital investment and would not significantly improve reliability. With groundwater being available as a backup supply, additional storage would only be required if groundwater levels continue to decline. In this instance, if a Managed Aquifer Recharge (MAR)scheme is technically feasible, it is likely to be a more cost effective storage alternative and should be investigated in preference to an additional surface water storage. For all of the above reasons, the option of further increasing the storage capacity is not likely to be cost effective and has not been considered further.
8.4.3 Increase System Capacity The pump station and pipeline from the Betka River currently have a maximum capacity of 1.2 ML per day, while the treatment plant has a capacity of 1.0 ML per day. EGW bulk entitlement allows maximum extraction of 1.55 ML per day when flow in the Betka exceeds 3.1 ML/day. Increasing the capacity of the infrastructure to accept the maximum bulk entitlement would increase extraction during high flow periods by 0.35 ML per day. This is unlikely to provide any significant benefit during extended dry periods when runoff from storm events is typically of short duration. Considering the limited additional supply that this option provides, it would only be cost effective if the works to upgrade the system were minimal. As such, this option has not been considered further.
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8.4.4 Treatment Plant Capacity The capacity of the treatment plant is 1.0 ML per day and during peak holiday periods the daily demand can exceed this capacity. During the peak periods the clear water storage is drawn down to meet demand. In the long-term, the treatment plant may need to be upgraded to meet demand, which is expected to increase over the planning horizon. Pressure on the supply system during peak periods could be alleviated by supplying alternative water sources to customers that use large amounts of water during those periods. The foreshore caravan park is the biggest water user in Mallacoota, which is the result of significant tourist numbers during the peak periods. An option to supply alternative water sources to the caravan park has been discussed in Section 8.3.2.
8.4.5 Optimising System Performance Analysis of the bulk water meter data from the last 3 years shows that during the periods when the Betka is flowing, less than 1.2 ML per day is generally extracted from the river. Discussions with the operators suggest that the system is capable of extracting 1.2 ML per day however there are a number of operational factors that prevent maximum extraction from occurring, including: x Storage levels – when the river begins flowing the operators take into consideration the available storage capacity and run the pumps at a constant rate over the estimated period of time that the river will flow. That is, the pumps are run at the minimum pumping rate required to fill the storages over that estimated time period. x Operation of the system – if possible the treatment plant can be operated at an increased flow rate to free up storage in the raw water basin, however this is not always possible if problems with algal blooms are occurring in the raw water basin.
While the bulk meter data that was analysed is limited, it shows that approximately 60 ML per year of allowable extraction of river water is not being utilised. While it won’t be possible to extract this entire amount, it is worthwhile getting a better understanding of the operational constraints and limitations associated with extracting the maximum amount from the river. It is recommended that EGW document the operational procedures for Mallacoota and review them on a reguilar basis (annually) to identify and monitor opportunities for improving the performance of the system.
8.5 Recycled Water (from the wastewater treatment plant) Most of the Mallacoota Wastewater Treatment Plant (WWTP) was constructed in 1987 along with the town’s sewerage system. Treatment is undertaken in a lagoon based system with winter storage to hold treated effluent during months when irrigation water is not required. Some of the treated effluent is provided to the Mallacoota Golf Course for irrigation purposes and the remainder of the treated effluent is used to irrigate pasture and tree lots. The EPA Discharge Licence for the treatment plant dictates a maximum discharge flow rate of 20 ML per month. Average annual inflows to the wastewater treatment plant are estimated at 9.5 ML per month. All of the treated wastewater is used either reused at the Golf Course or on pasture and tree lots. The water is supplied to the Golf Course under an agreement signed in the 1990s. Under the agreement the Golf Course receives recycled water without charge. There may be the opportunity to supply additional recycled water to the Golf Course or other customers to achieve potable savings. Potable savings can be achieved either by supplying end uses that do not require potable standard water, such as open space use or toilet flushing, or by indirect potable use where the treated wastewater is released into the water supply system and combined with existing sources for potable consumption. The Victorian Government’s White Paper, Our Water, Our Future, rules out indirect potable use as an option and as such it is not considered further here. It may however become an option in the future as technologies and perceptions change.
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The Caravan Park uses almost 16 ML of water per year and could potentially use recycled water for toilet flushing and open space irrigation. This would require an upgrade to the treatment plant to provide Class A water and the installation of a pipeline. Supplying recycled water is not expected to be cost effective compare dot supplying other sources such as rainwater or groundwater. These options have been discussed further in Section 8.3.2. It is understood that the Golf Course is interested in using more recycled water than they are currently receiving. Increasing supply of recycled water to the Golf Course will be the most cost effective option, given that the infrastructure is already in place. As such, this option has been taken forward for further analysis.
8.6 Rainwater A preliminary rainfall analysis was undertaken to establish whether or not the installation of rainwater tanks could be a viable alternative water supply. The analysis determined that for an average daily demand of 343 L/house/day, rainwater could supply of 15% of the total household demand (or 51 L/day) at a reliability of around 90% with the installation of a tank size of 15,000L (assuming a collection area of 175 square meters per house). As the construction of new dwellings within the township is predicted to be minimal, rainwater tanks would need to be retrofitted into existing homes. This can most economically be accomplished by supplying outdoor uses only as the cost of retrofitting indoor appliances (i.e. toilets and washing machines) is more expensive. This limits the ability of this supply source to supply demands during the critical period when most of the town’s demand is comprised of un-restrictable indoor water use. The cost of retrofitting rainwater tanks to households is likely to be cost prohibitive and has not been considered further. While the installation of rainwater tanks on individual houses is likely to be cost prohibitive, the option of using rainwater for large users may be a more viable option. Supply of rainwater to the caravan park has been considered further and is discussed in Section 8.3.2.
8.7 Stormwater Stormwater could be harvested on a large scale to substitute potable consumption. Stormwater harvesting involves the storage, treatment and delivery of water to a customer or a number of customers. The storage generally has to be quite large to capture flows during high rainfall events. The treated stormwater is generally used for non-potable end uses. There are a number of constraints to a stormwater harvesting scheme in Mallacoota, including: x There is unlikely to be sufficient existing stormwater infrastructure to make this a viable option x A large storage would be required x A large user or users who could accept treated stormwater to substitute current potable usage would need to be identified. x These end uses could also be supplied with recycled water for which there exists a readily available supply
Supplying large non potable demands, such as demand at the caravan park, would be more cost effective than retrofitting existing residential dwellings with a third pipe arrangement, especially when a reliable source of groundwater already exists. In the case of the caravan park, the viability of rainwater should considered first as treating stormwater to a suitable standard is much more complex. The option of harvesting rainwater to supply the caravan park has been discussed further in Section 8.3.2. Due to these limitations and constraints, stormwater harvesting has not been taken forward as an option.
8.8 Water Cartage Water carting should only be considered as an emergency supply in the event that Mallacoota’s water storages approach critically low levels. In this situation, water carting would be required infrequently and is therefore financially viable compared to investing in large infrastructure that may be used infrequently or not at all.
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Water carting surface water would either need to come from Genoa (20 km), Wigan (45 km) or Cann River (72 km). Given that the Genoa River is often dry it is likely that water would need to be carted some distance and an alternative emergency solution should be investigated if groundwater becomes unreliable. EGW are currently investigating the possibility of installing a groundwater bore at Gipsy Point, which could potentially be used for emergency supply to Mallacoota.
8.9 Options to be Considered Further A number of water supply options have been identified for Mallacoota in the previous sections. These options can be described as either supply augmentation options or emergency supply options. The following supply augmentation options will be considered further: x Option 1 – Install additional groundwater bores x Option 2 – Managed Aquifer Recharge x Option 3 – Demand management for high water users x Option 4 – Cover raw water storage x Option 5 – Supply additional recycled water to the Golf Course x Option 6 – Supply recycled water to other customers x Option 7 – Supply an alternative water source (rainwater/groundwater) to the Caravan Park
In addition to the supply augmentation options listed above, the following emergency supply options will also be considered in the multi criteria analysis (MCA): x Water carting x Mobile desalination
Reduction in system leakage has not been assessed through the TBL as it is not expected to have a significant impact on security of supply, however EGW should continue the current practice of minimising system losses and improving efficiency. Options that have not been considered further include: x Extracting water from the Genoa River has not been considered further due to the length of pipeline required to connect these sources to the existing supply system x Accessing the deep pools on the Betka River should only be considered as a last resort and is unlikely to provide significant additional supply x Additional surface storage would provide minimal additional reliability and would therefore not be cost effective x The cost of retrofitting households to supply rainwater is not expected to be cost effective x The infrastructure required for a stormwater harvesting scheme is not considered to be cost effective x Increasing the capacity of the pumps, pipeline and treatment to the bulk entitlement level is not expected to be cost effective given the limited additional supply that it would provide
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9.0 Assessment of Supply Options using MCA To assess the options available for securing Mallacoota’s water supply system, a Multi Criteria Analysis (MCA) has been undertaken. The MCA has been based on the methodology used in the Central Region Sustainable Water Strategy as it is anticipated that this methodology will also be adopted for the Gippsland Sustainable Water Strategy currently being prepared by DSE.
9.1 Selection of Criteria The criteria in Table 15 have been used to qualitatively assess the impact of each option.
Table 15: MCA Criteria for Assessment
Criteria Measure Economic Net Present Cost Comparative Assessment Environmental Greenhouse Gas Emissions Comparative Assessment Impact upon environmental flow objectives Estimated relative impact Impact on surface, ground and marine water quality Estimated relative impact
Estimated loss or gain of significant ecological vegetation Impact on terrestrial ecosystems classes Recreation and Heritage Estimated impact on recreation and heritage Social
Estimated degree of opposition or acceptance by the local Social Acceptability community Reliability of Supply Confidence of Success Level of confidence in option Potential increase in the volume of water available during Volume of water provided critical supply periods
9.2 Scoring All criteria are scored on a scale from -5 to +5, where -5 generally represents a relatively negative impact or cost and +5 generally represents a relatively high degree of benefit. Scores around 0 are generally neutral impacts or mid-range costs.
9.3 Weightings Weightings have been applied to each of the criteria based on their relative importance to EGW. Economic and Reliability of Supply criteria are considered to be equally the most important criteria as EGW has a commitment to meet its LOS objectives for its customers, while being required by legislation and regulated by the ESC to minimise the cost burden to its customer base. Environmental impacts are also given a significant weighting as EGW recognises the interactions between urban water supply, river health and greenhouse gas production. The final criteria is Social, which is not considered as sensitive in this situation where no proposal exists to transfer water from farming to urban use. The weightings applied to each group of criteria are shown in Table 16.
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Table 16: MCA Weightings Weighting Criteria (%) Economic 35 Environmental 20 Social 10 Reliability of Supply 35
9.4 Results The results of the MCA for the supply augmentation options and the emergency supply options are presented in Section 9.5, Table 16 and Table 18 respectively.
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Table 17: MCA results for the supply augmentation options
Option 7 – Option 1 - Option 2- Option 5 - Option 6 - Alternative Additional Managed Option 3 - Option 4 - Recycled Recycled water sources groundwater Aquifer Demand Cover raw Water to Golf Water to other for the Bores Recharge Management water storage Course users Caravan Park Economic (35%) Net Present Cost 0.0 -2.0 2.0 -1.0 1.0 -3.0 0.0 Average Economic 0.0 -2.0 2.0 -1.0 1.0 -3.0 0.0 Weighted Economic 0.0 -0.7 0.7 -0.4 0.4 -1.1 0.0 Environmental (20%) Greenhouse Gas Emissions -2.0 -2.0 3.0 3.0 -2.0 -3.0 -1.0 Impact upon environmental flow objectives -1.0 -1.0 2.0 2.0 1.0 1.0 0.0 Impact on surface, ground and marine water quality -1.0 -1.0 0.0 0.0 1.0 1.0 -1.0 Impact on terrestrial ecosystems -1.0 -1.0 0.0 0.0 0.0 -1.0 0.0 Recreation and Heritage 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Average Environmental -1.0 -1.0 1.0 1.0 0.0 -0.4 -0.4 Weighted Environmental -0.2 -0.2 0.2 0.2 0.0 -0.1 -0.1 Social (10%) Social Acceptability 1.0 1.0 -1.0 1.0 1.0 1.0 0.0 Average Social 1.0 1.0 -1.0 1.0 1.0 1.0 0.0 Weighted Social 0.1 0.1 -0.1 0.1 0.1 0.1 0.0 Other Criteria (35%) Confidence of Success 2.0 1.0 3.0 3.0 3.0 1.0 2.0 Volume Supplied 3.0 2.0 1.0 1.0 1.0 2.0 1.0 Average Other 2.5 1.5 2.0 2.0 2.0 1.5 1.5 Weighted Other 0.9 0.5 0.7 0.7 0.7 0.5 0.5 Overall Score 2.5 -0.5 4.0 3.0 4.0 -0.9 1.1 Weighted Overall Score 0.8 -0.3 1.5 0.7 1.2 -0.5 0.4
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Table 18: MCA results for the emergency supply options Water Mobile Carting Desalination Plant
Economic (35%) Net Present Cost -1.0 -4.0 Average Economic -1.0 -4.0 Weighted Economic -0.4 -1.4 Environmental (20%) Greenhouse Gas Emissions -3.0 -5.0 Impact upon environmental flow objectives -1.0 0.0 Impact on surface, ground and marine water quality -1.0 -1.0 Impact on terrestrial ecosystems 0.0 -1.0 Recreation and Heritage 0.0 0.0 Average Environmental -1.0 -1.4 Weighted Environmental -0.2 -0.3 Social (10%) Social Acceptability 1.0 -2.0 Average Social 1.0 -2.0 Weighted Social 0.1 -0.2 Other Criteria (35%) Confidence of Success 3.0 2.0 Volume Supplied 1.0 2.0 Average Other 2.0 2.0 Weighted Other 0.7 0.7 Overall Score 1.0 -5.4 Weighted Overall Score 0.3 -1.2
9.5 Discussion 9.5.1 Water Supply Augmentation The water supply augmentation options scored in the following order, from highest to lowest: x Demand management x Supply additional recycled water to the golf course x Construction of an additional groundwater bore/s and an increase in EGW’s groundwater licence x Cover the raw water storage x Supply an alternative water source to the caravan park for non-potable uses x Managed aquifer recharge x Supply recycled water to additional customers
Demand management scored the highest in the MCA. EGW has already installed a PRV at the caravan park to limit pressure and water consumption during the peak periods. EGW should further pursue demand management by conducting an audit of high water users to understand their water use patterns and effectively tailor demand management initiatives. Although demand management is a cost effective means of improving reliability of supply it will need to be combined with other solutions to secure Mallacoota’s future water supply.
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The next highest scoring option was supplying additional recycled water to the golf course. This option scored well because the infrastructure is already in place and requires little capital investment. This option provides an additional water supply but will be limited to a relatively small amount that can be utilised by the golf course. Construction of new groundwater bores scored the third highest and will diversify Mallacoota’s water supply. It is understood that EGW is currently investigating a suitable locations for new groundwater bores. This option performed slightly better than covering the raw storage as it is likely to incur lower capital cost and will provide a greater volume of water. Covering the raw water storage was assessed assuming that the funding application is successful. If funding is granted, this option should be implemented, however if funding is not secured it does not provide a cost effective option, dropping the overall weighted score of this option to 0. The option of suppling an alternative water source to the caravan park scored the next highest. While it was not one of the top scoring options, it has the benefit of reducing demand during the peak periods when the treatment plant is running at capacity. This option could have additional cost benefits associated with delaying future upgrades to the treatment plant by reducing demand of potable water during the peak periods, which have not been considered in the MCA. . The options of managed aquifer recharge and supply of recycled water to additional customers all involve significant capital cost and should only be considered if groundwater levels continue to decline across the aquifer.
9.5.2 Emergency Supply As streamflows have become less and less reliable, reliance on groundwater has increased. It is likely that groundwater will provide Mallacoota’s bulk supply in the future. In the event that groundwater extraction has to cease for a period of time an emergency supply needs to be available. Of the emergency supply options assessed, water cartage either from a surface water or groundwater source scored higher in the MCA than a mobile desalination plant. This is primarily a result of the cost and the environmental impacts associated with desalination. Whilst water carting will be costly due to the distance to a reliable water source, it will be a very rare event and therefore provides a suitable emergency supply. While a mobile desalination plant did not score well here, it may have some merits if used across EGW‘s entire area of service. The value of this could be assessed upon completion of the remaining WSDS’s for EGW. Limited brine disposal options at other locations is likely to be the main impediment to the viability of this option.
9.6 Expected Scheme Costs The proposed scheme to improve reliability of supply to Mallacoota is: x Improve reliability of supply by: - Completing water use audits of high water users to identify potential water efficient projects - Investigating the possibility of supplying additional recycled water to the golf course - Constructing new groundwater bores - Increasing EGW’s groundwater licence to 220 ML/yr - Covering the raw water storage if funding is granted - Supplying an alternative water source to the caravan park x Provide emergency supply by: - Water carting
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An estimated concept cost for each of these options is presented in Table 19.
Table 19: Expected Scheme Costs Scheme Component Conceptual Cost ($) Water efficiency projects Pending water use audits Additional recycled water to golf course Negligible assuming transfer capacity exists Construct new groundwater bores $100,000 (assuming 2 bores) Emergency carting Dependant on source, likely to be in excess of $5,000/ML Covering the raw water storage (50% $240,000 external funding) Supply alternative water source to the $60,000 Caravan Park
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10.0 Stakeholder Consultation Stakeholder consultation was undertaken as part of the 2007 WSDS. As this WSDS forms an interim document, stakeholder consultation has not been undertaken.
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11.0 Conclusions and Recommendations
11.1 Conclusion With scientific evidence suggesting that climate change is tracking along the driest of scenarios, it is likely that the Betka River will not provide a reliable source of water for Mallacoota into the future. In addition there is significant uncertainty around how groundwater supplies will be impacted by climate change. A number of modelling scenarios were used to determine EGW ability to meet its LOS objectives in Mallacoota. The results showed that the LOS objectives can be met under a high impact scenario (continuation of low flows and high population growth) by the continued reliance on groundwater. Preliminary evidence suggests (refer to Appendix A) that the licensed extraction volume of groundwater is within the sustainable yield of the aquifer. However, the data also shows that the groundwater levels have declined over the last 3 years. This observed decline, combined with the likelihood that the recharge rate will be affected by climate change, creates significant uncertainty about the reliability of groundwater in the long term. It is recommended that EGW continue to use groundwater as an integral part of supply to Mallacoota and closely monitor and review groundwater level data. If groundwater does become an unreliable source, EGW should review this WSDS and re-evaluate the options presented in this strategy to secure Mallacoota’s supply.
11.2 Summary of Recommendations Following this update of the WSDS for Mallacoota, it is recommended that EGW action the following strategies for the Mallacoota water supply system. Implementing all of these recommendations will be resource intensive and EGW should prioritise implementation in accordance with the below action plan.
Table 20: Action Plan Action Implementation Monitor groundwater levels in accordance with the BE requirements and assess long term Immediate trends in groundwater levels. If levels continue to decline across the aquifer, this WSDS should be reviewed as higher cost supply alternatives may become viable. Apply to increase the existing groundwater licence to 220 ML/yr Immediate Seek to reduce current water demand by auditing high water users in Mallacoota and Immediate identifying possible savings Identify supply sources for water carting and if appropriate, formalise emergency access into Immediate the existing bulk entitlement Investigate whether an initial Managed Aquifer Recharge feasibility assessment could be Immediate cost effectively combined with ongoing groundwater investigations at Mallacoota Update Mallacoota’s Drought Response Plan Immediate Continue the current practice of extracting water from the Betka River during times of flow Ongoing Continue to use groundwater as an integral part of Mallacoota’s water supply by constructing Ongoing new bores to ease the pressure on the existing bores and also investigate the potential for a drought relief bore Document the operational procedures for the Mallacoota system and review on an annual Ongoing basis to identify and monitor opportunities for improving the performance of the system. Continue existing leak detection programs to ensure the system operates in an efficient Ongoing manner. Continue to seek a reduction in the area to be logged within Mallacoota’s water supply Ongoing catchment Evaluate the feasibility of a regional mobile desalination plant upon completion of the July 2010 remaining WSDS’s Investigate the feasibility of providing either groundwater, rainwater or a combination of both 2011 to the Caravan Park to reduce their reliance on mains water particularly during peak periods Investigate the feasibility of providing additional recycled water to the golf course 2011 Cover the raw water storage if funding is secured Longer term
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Appendix A
Review of Groundwater Data
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Appendix A Groundwater
To examine the reliability of groundwater supply from existing East Gippsland Water (EGW) bore infrastructure at Mallacoota, AECOM has reviewed: x Bore data supplied by EGW x GHD Report “East Gippsland Water. Licence Increase Application – Groundwater License 9016496” dated August 2008.
The analysis has been based on a total annual extraction of 120 ML. While the current extraction volume for Groundwater License number 9016496 is 80 ML per year, it is possible that the license will be increased pending further investigations by EGW.
Existing Conditions Groundwater is currently extracted from two bores, Bore 142799 (Betka Bore) and Bore 142800 (Mallacoota Treatment Plant Bore). Bore 142799 was installed in September 2000 to a total depth of 84.5 metres below ground surface (mbgs) and screened from 44.5 to 84.5 mbgs across weathered Ordovician sediments. Standing water level was reportedly 5.2 m. Bore 142800 was installed in October 2000 to a total depth of 86.9 mbgs and screened from 40.9 to 81.5 mbgs across weathered Ordovician sediments. Standing water level was reportedly 10.5 m. Reported hydrostratigraphy for the area indicates that the weathered Ordovician sediments intercepted by these bores, is overlain by approximately 25 m of Tertiary overburden belonging to the Haunted Hill Formation. These unconsolidated sediments reportedly have a high clay content and form a confining layer. This confining layer acts as a hydraulic barrier reportedly preventing extractions from the fractured bedrock aquifer impacting the watertable or surface water features. This barrier will help to protect the deeper groundwater and isolate it from surface effects. Based on pumping test analysis completed by Geo-Eng Pty Ltd in November 2000, the Transmissivity of the bores were estimated to be 20-25 m2/day for Bore 142799 and 134-137 m2/day for Bore 142800. Storage coefficients were estimated to be approximately 10-3 to 10-4 for the weathered Ordovician bedrock (GHD, 2008).
Impacts from Climate Change Similar to surface water supplies, groundwater is also susceptible to climate change and increasingly drier conditions may result in a significant reduction in the volume of water available for extraction. To consider the effect that climate change may have on the availability of groundwater, a 10% decrease in the average annual rainfall was evaluated (i.e. dry scenario). Rainfall data for the area taken from the Bureau of Meteorology for Mallacoota, indicates that from 2006 to 2008 the average annual rainfall was 831 mm. For the period 1974-2008, the average annual rainfall for the region was estimated to be 941 mm. Overall, rainfall appears to have decreased slightly over the recorded time period (note that some of the rainfall data has not been quality controlled by the Bureau of Meteorology). If it is assumed that rainfall may decrease a further 10% (from 831 mm), the rainfall may drop to 748 mm/year. Given a typical recharge rate of 5% (GHD, 2008) and an estimated total area of exposed bedrock aquifer of 15.2 km2 (GHD, 2008), the estimated annual volume of recharge available over the area is calculated to be 569 ML. It should be noted that an evaluation of the assumptions made in previous investigations, such as the recharge rate of the aquifer, has not been performed and should be considered. It is possible that the recharge rate will decease if the climate becomes drier. If the total allocation of groundwater extraction is 120 ML for Groundwater License 9016496 and 2 ML is allocated for other Stock and Domestic used in the region (122 ML total allocation), this would represent less than 22% of the annual recharge estimate for the catchment. It is therefore considered that, given a 10% reduction in rainfall due to climate change, the current allocation to 120 ML/yr is well within the sustainable yield of the aquifer even under conditions of lower rainfall.
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Reliability of the Aquifer Water level data for the two extraction bores over the period October 2006 to November 2009 show fluctuating levels generally corresponding to daily extraction rates. Both wells show an overall trend of decreasing water levels (around a 3 - 5 m) over the three year period, indicating increased drawdown corresponding to increased pumping rates. They also show good recovery following water extraction events, indicating water available in storage. Pump test data for Bore 142799 recorded by Geo-Eng in 2000, indicated that at a pumping rate of around 5.8 L/s, drawdown after 24 hours was around 15.4 m. For Bore 142800, the recorded drawdown after 24 hours was approximately 4.4 m. In June 2007, a drawdown of approximately 19.0 m was recorded for Bore 142799 at an average daily pumping rate of approximately 5.7 L/s. Compared to the pumping test data collected in 2000, this indicates that approximately 19% of the available drawdown was being used. In August 2009, Bore 142800 recorded a drawdown of approximately 6.1 m at an average daily pumping rate of approximately 5.7 L/s. This indicates that approximately 28% of the available drawdown was being used Based on the aquifer properties (GHD, 2008) and well construction, an assessment was conducted to evaluate whether the two existing bores are physically capable of providing the 120 ML allocation. The Cooper-Jacob approximation to the Theis equation was used for this evaluation. It was also assumed that the wells are 80% efficient, the drawdown does not drop below the top of the screen, and well interference is ignored. The results of the calculations suggest that the maximum pumping rate for the two wells in combination is approximately 780 m3/day or 280 ML/yr. Therefore, the existing wells should be able to provide the full allocation volume. In February 2009, the average daily extraction rate for Bore 142800 exceeded 1500 kL and the water level in this bore subsequently fell to approximately 40 m bgs, just above the reported screen interval of this bore. Based on this data and the pumping tests conducted by Geo-Eng in 2000, to prevent overpumping of the wells it is recommended that a pumping rate of 10 L/s or 864 kL/day should not be exceeded as recommended by GHD (2008). It should be noted that the impact to surrounding water features and other regional bore users has not been considered here. The reliability of groundwater supply from Bores 142799 and 142800 as indicated from water level data taken from October 2006 to the present and recorded average daily extraction rates, suggests that these wells are in good condition and that the water allocation of 120 ML is well within the sustainable yield of the aquifer and that the existing bores should be capable of extracting this volume. Given that the Mallacoota Treatment Plant Bore (142800) has a higher transmissivity than the Betka bore (142799), this well is expected to be the most reliable groundwater supply bore of the two and contribute the greater volume of groundwater to the overall water allocation.
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Appendix B
Modelling Methodology and Assumptions
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Appendix B Modelling Methodology and Assumptions
The method adopted for the REALM modelling can be summarised as: x Review previous WSDS model (SKM, 2007) and identify any issues x Collate streamflow data and update where possible x Model impacts of climate change and population growth on water supply x Undertake modelling and produce output graphs.
Streamflow Data There are two gauging stations on the Betka River for which data could be found; Betka River at Mallacoota (221203) and Betka River at Miners Track (221218). The Mallacoota record is from February 1970 to July 1972 and the Miners track record runs from January 1996 to July 2000. East Gippsland Water operations staff from the Mallacoota Depot were able to provide records of readings which they have been making from 2006 to the present time. Given the lack of overall stream flow data the results from the HYDROLOG model from the previous report was used in the REALM model to make up the majority of the stream flow record. Gauged stream flow was only used from 2006 to present.
Assumptions The key assumptions made during the modelling exercise are summarised in Table 21.
Table 21: REALM Modelling Assumptions Data Assumptions Streamflow Data x The streamflow estimates from the HYDROLOG model, which SKM created as part of the DRP, were assumed to represent a good relationship between rainfall and runoff and were used for data between 1900 and 2005 x Between 2005 and 2006 median weekly flow values were used to extend the flow record x From 2006 to 2009 EGW provided readings from the Mallacoota Depot operations group. These readings were generally weekly and were averaged to create an additional 3 years of streamflow data. Missing values were filled in with averages. Groundwater Data x The total groundwater bulk entitlement is 120 ML/year x The rate of ground water extraction is assumed to be 0.4 ML/day (when required) x The groundwater bores will operate whenever the total storage level in the raw water and clear water tanks drops below 90% (total volume of 57.6 ML) x The effect of drawdown on bores is not modelled. Demand Data x The total annual average demand is assumed to be 160 ML/year x The data from the previous model was factored down to 160 ML/year in order to maintain the same peaking rates over summer and winter. The previous demand data model was not checked. It was assumed to be sufficient in the form it was provided x For demand data beyond 2005 (where the previous demand model ended) average demand figures for each week of the year were used x Two scenarios were modelled with increased population growth. The rate of growth is assumed to be 0.32% for the moderate scenario and 0.8% for the high scenario. This led to a total demand increase of 6.9 % being applied for the moderate scenario and 18.2% for the high scenario. It is assumed that demand increases at
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Data Assumptions the same rate as population. Climate Change x The impacts of climate change will be realised by 2030, after this time there will be no further reduction in streamflow due to climate change x The reduction in streamflow will occur in a linear fashion, reducing by a fixed amount each year between 1990 and 2030 x The predicted reduction in streamflow is outlined in Section 6.1. REALM Model x The REALM model uses a weekly time step – this may understate the effect of a few days of low or no flow on reservoir storage levels; and x The rate of extraction from the Betka River is assumed to be 1.2 ML/day – if the flow in the Betka River drops below 3 ML/day then only half of the flow may be extracted. x The groundwater bores and the Betka River offtake can operate simultaneously.
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Appendix C
Additional Modelling Results
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