Swifts Creek Water Supply Demand Strategy Swifts Creek Water Supply Demand Strategy AECOM

11 May 2010

Swifts Creek 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

11 May 2010

60144336 Task 1.02

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11 May 2010 Swifts Creek Water Supply Demand Strategy AECOM

Quality Information

Document Swifts Creek Water Supply Demand Strategy

Ref 60144336 Task 1.02

Date 11 May 2010

Prepared by Mandy Habener

Reviewed by Steven Wallner

Revision History

Authorised Revision Revision Details Date Name/Position Signature

A 22-Mar-2010 Draft for Internal Review Elisa Hunter Original Signed Principal Engineer - Water B 24-Mar-2010 Draft for Client Comment Elisa Hunter Original Signed Principal Engineer - Water C 20-Apr-2010 Final Draft for Issue Andrew Grant Original Signed Principal Engineer - Water D 10-May- Final for Issue Andrew Grant Original Signed 2010 Principal Engineer - Water E 11-May- Revised Final for Issue Andrew Grant Original Signed 2010 Principal Engineer - Water

11 May 2010 Swifts Creek Water Supply Demand Strategy AECOM

Table of Contents Executive Summary i 1.0 Introduction 1 1.1 Regional Setting 1 2.0 Current Water Supplies 3 2.1 Description of Water Supply System 3 2.2 Allocations of Water 4 2.2.1 Bulk Entitlements 4 2.2.2 Licensed Diversions 4 2.2.3 Groundwater Licences 5 2.2.4 Level of Service Objectives 5 2.3 Historical Water Restrictions 5 3.0 Previous Studies, Legislation and Regulation 7 3.1 Previous Long Term Planning Studies 7 3.1.1 Drought Response Plan for Swifts Creek (SKM, 2006) 7 3.1.2 EGW Water Supply Demand Strategy (SKM, 2007) 7 3.2 Regulations and Legislation 7 4.0 Water Demand 10 4.1 Current Demand 10 4.1.1 Previous Demand Estimates 10 4.1.2 Bulk water meter data and historical diversions 10 4.1.3 Water Consumption and Connections Data 11 4.1.4 Industrial/Commercial Water Use 12 4.1.5 Unaccounted Water 12 4.1.6 Summary of Current Demand 12 4.2 Forecast Water Demand 12 4.2.1 Previous Population Projections 12 4.2.2 Recent Census Data 13 4.2.3 Victoria in Future Data 13 5.0 Demand Management and Reduction 14 5.1 Measures to Achieve Demand Reduction Targets 14 5.1.1 Current Demand Reduction Initiatives (SKM, 2007) 14 5.1.2 Future Demand Reduction Initiatives (SKM, 2007) 15 6.0 Water Supply 17 6.1 Future Reliability of Surface Water 17 6.1.1 Impact of Climate Change 17 6.1.2 Step Change 17

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6.2 Impact of Bushfires 18 6.2.1 Background 18 6.2.2 Previous Bushfires 18 6.2.3 Future Bushfires 19 6.2.4 Proposed Fuel Reduction 19 6.3 Forestry 19 6.4 Future Streamflow Projections 19 7.0 Reliability of Supply 21 7.1.1 Method Overview 21 7.1.2 Modelling Assumptions 21 7.2 Current Reliability of Supply 22 7.3 Future Reliability of Supply 24 8.0 Options for Managing Water Supply 28 8.1 Groundwater 28 8.2 Water Loss Reduction 28 8.3 Water Carting 28 8.4 Recommendations for Managing Supply 29 9.0 Stakeholder Consultation 30 10.0 Conclusions and Recommendations 31 11.0 References 32

11 May 2010 Swifts Creek Water Supply Demand Strategy AECOM

Executive Summary Water Supply Demand Strategies (WSDS) aim to ensure that an appropriate balance is maintained between urban water supply and demand over the long term planning horizon of 50 years. East Gippsland Water (EGW) finalised their WSDS for all water supply systems during 2007 and is in the process of reviewing each of the water supply strategies. AECOM Australia Pty Ltd (AECOM) has been engaged by EGW to revise their existing WSDS for the Swifts Creek water supply system. This revised WSDS will replace the strategy set out for Swifts Creek in EGW’s overall WSDS (Section 14). 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 Swifts Creek’s current water supply system for meeting current and future water demand. An assessment of current reliability of supply (based on the existing system) was undertaken to determine its reliability with regard to EGW’s LOS objectives. The assessment showed that under current arrangements voluntary restrictions would be required on average once in every 3 years and Stage 2 restrictions would be required once in every 4 years. This is significantly more frequent that EGW’s LOS objective of Stage 2 restrictions being required no more frequent than once every 10 years. Both Voluntary and Stage 1 triggers are currently based upon streamflow and as a result the storage rarely draws down, yet restrictions are triggered frequently. This indicates that Swifts Creek’s water supply system is very reliable although revision of the restriction triggers is required to ensure that LOS objectives can be met in the future. To gain an understanding of how security of supply in Swift’s Creek is likely to change with the impacts of climate change, bushfire impacts and population growth, the system was modelled at 2060. The input parameters for modelling were as follows:

Table E1: 2060 Modelling Parameters Modelling Parameter Adopted Value Climate Change Reduction in Streamflow (2060) -27.2% Bushfire Reduction in Streamflow (2060) -5% Growth Predictions (per annum) 0.6% (2006 to 2026) and 0.5% (2027 to 2060)

Revised restriction triggers were developed to demonstrate that under reduced flow conditions LOS objectives can be achieved. Both the previous and revised restriction triggers (for future situation modelling) are summarised in Table E2.

Table E2: Previous and Revised Restriction Triggers Level of Restriction Previous Triggers Revised Triggers Voluntary Streamflow = 15ML/day Streamflow = 2ML/day Stage 2 Streamflow = 5ML/day Storage = 4ML Stage 4 Storage = 2ML Storage = 1.5ML

The 2060 modelling scenario gave the following response times and service levels.

Table E3: Response times and service levels for revised restriction triggers Level of Restriction Remaining Supply Restriction Frequency Voluntary 40 days 1 in 7 years Stage 2 32 days 1 in 32 years Stage 4 14 days 1 in 62 years

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It can be seen from Table E3, that LOS objectives at Swifts Creek can be met under changing climate conditions when considering the impacts of bushfires and population growth by simply revising the current restriction triggers to those shown in Table E2. The revised restriction triggers provide 8 days of storage between the Voluntary and Stage 2 restriction trigger and a further 18 days between the commencement of Stage 2 and Stage 4 restrictions (during the peak month assuming no rainfall). Given the results of the REALM modelling it is considered un-necessary for EGW to make changes to the current infrastructure at Swifts Creek. In times of water shortage it is recommended that EGW supplement the storage by topping it up with groundwater from the drought relief bore or in an emergency cart water from the Mitta Mitta River or other surrounding towns. Based on the modelling undertaken and the assessment of options it is recommended that EGW undertake the following to secure Swifts Creek’s water supply: x Revise their restriction triggers so that LOS objectives can be met; x Continue to monitor and strive to reduce losses within the water supply system; x Use the groundwater bore to supplement surface water flows during times of drought/water shortage; x In times of emergency, cart water from the Mitta Mitta River or another alternative supply system. x Continue to monitor the impacts of logging and if a long term supply shortage is anticipated seek a reduction in the area to be logged within the water supply catchment; x Formalise emergency access to the Mitta Mitta River for water carting into the existing bulk entitlement; x Update Swifts Creek’s Drought Response Plan.

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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 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 resulting from the combined impacts of the ongoing drought, climate change and bushfires. WSDS are otherwise required to be reviewed and updated at least every 5 years. Continuing dry conditions have resulted in a significant drop in streamflows throughout Victoria and East Gippsland has not been exempt from these impacts. CSIRO have 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 preparations of the earlier WSDS may over estimate long term yields. The previous WSDS for Swifts Creek recommended that EGW: x Reduce uncertainty in current estimate of consumer demand x Reduce uncertainty in future estimate of consumer demand x Encourage demand reduction x Manage the potential long-term effects on supply reliability due to the 2003 bushfires

In accordance with the WSDS review process, this document forms a revised WSDS for the Swifts Creek water supply system and will replace the strategy set out in EGW’s overall WSDS (Section 14). 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 Swifts Creek is a small saw-milling town situated on the Great Alpine Road approximately 120 km north of Bairnsdale and 380 km east of Melbourne. The town is located on the banks of the Tambo River at its junction with Swifts Creek. The 2006 census showed that Swifts Creek and the surrounding area had a population of around 280 people. The location of Swifts Creek is shown in Figure 1 as follows.

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Figure 1: Regional Map (to be replaced with a GIS map in the final revision)

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2.0 Current Water Supplies

2.1 Description of Water Supply System The primary water supply for Swifts Creek comes from surface waters diverted from the Tambo River. The Tambo River catchment covers an area of approximately 739 km2 which is largely forested with some farmland areas. SKM (2009) stated that the vegetation types within the catchment consist of ash, mixed eucalypt and snow gum (78%) and grassland areas (22%). The pumping station has the capacity to transfer 12.6 L/sec (or 1.1 ML/day) of raw water via a 1.26km, 150mm diameter rising main. This rising main supplies the water treatment plant, with treated water being stored in a 4.6 ML clear water basin. During July of 2008 EGW commissioned a new water treatment plant at Swifts Creek to improve the quality of treated water provided to the town. The treatment plant uses a Dissolved Air Flotation Filtration (DAFF) process which is capable of treating raw water from the Tambo River to a standard of less than 0.3 NTU (Turbidity) and less than 5 Pt/Co (Colour). The treatment plant has been designed with a treatment capacity of 8 L/sec giving a total daily volume of 0.7 ML/day. A groundwater bore (95742) can be used to supplement surface water supplies during times of drought. In the past water from the bore has been pumped by installing a temporary pipeline which runs through a culvert into an existing transfer pump station. The water is then transported to the storage basin and is mixed with the diverted surface waters to provide an increased volume of water. It has been reported by SKM (2007) that the capacity of this bore is 0.11 ML/d (1.3 L/sec). Discussions with operations staff indicate that this bore is relatively low yielding with a small flow rate and an available pumping time of around half an hour (with a half hour recovery time). Based on this information the daily yield from this bore can be estimated at around 0.05 ML/day. The location of the bore in relation to other infrastructure is shown in Figure 2.

Figure 2: Swifts Creek Water Supply Infrastructure

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A schematic of the Swifts Creek water supply system is shown in Figure 3.

Figure 3: Swifts Creek Water Supply System

2.2 Allocations of Water 2.2.1 Bulk Entitlements East Gippsland Water has a bulk water entitlement of 224 ML per year for the Tambo River which is subject to the following flow sharing arrangements: x When the flow is less than or equal to 1.1 ML/day then EGW’s entitlement is equal to the flow in the Tambo River upstream of the town off-take x When the flow is above 1.1 ML/day then EGW’s entitlement is 1.1ML/day

This entitlement was outlined in the Victorian Government Gazette on the 4 September 1997; this can be seen at http://gazette.slv.vic.gov.au/view.cgi?year=1997&class=general&page_num=2383&state=V&classNum=G35&sea rchCode=475083

2.2.2 Licensed Diversions Southern Rural Water (SRW) provides an overview of local management rules for each of their river catchments on a regular basis. The latest revision of these rules was issued in September 2009. The management rules not only provide operational guidelines, but also a summary of licences held. A summary of licences for the Upper Tambo River is shown in Table 1.

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Table 1: Number and Volume of Licences issued for the Upper Tambo River (SRW, 2009) Number of Volume licences (ML) Direct Pumping 14 497.6 Domestic and Stock Licences 39 100 Bulk Entitlements (EGW) 1 224 Miscellaneous (toilet blocks etc) 1 2.2 Winter fill 1 8 Total 56 831.8

From Table 1 it can be seen that the volume of water available to private diverters in the upper Tambo River is 607.8 ML/annum. EGW makes up the remaining licensed volume of 224 ML/annum with their Bulk Entitlement. The majority of the diversions are for irrigation, which takes place from November to May. Within the ‘Local Management Rules’ for the Tambo Catchment SRW (2009) states: “The Tambo Upper flows tend to be fickle in dry periods, often resulting in the need to apply total bans to irrigators. Total ban applies to all irrigation licences on upstream waterways above the Little River when streamflow at the Swifts Creek Gauge falls below 4ML/day.” This indicates that EGW’s surface water supply for Swifts Creek should not be comprised by upstream diversions during low flow periods.

2.2.3 Groundwater Licences EGW does not hold a formal licence for the drought relief bore (no. 95742) at Swifts Creek. In the event of this bore being required for drought relief, EGW would need to seek temporary approval from the licensing authority (in this case SRW).

2.2.4 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; and 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/Water/WaterRestrictions/tabid/95/Default.aspx Swifts Creek is currently subject to Permanent Water Saving Rules (which are being applied as part of a Victoria wide strategy).

2.3 Historical Water Restrictions A search of EGW’s archives found the following historical events relating to changes in water restrictions for Swifts Creek: x January 1998 – Stage 2 restrictions introduced x Mid 1998 – Restrictions lifted x January 2003 – Voluntary restrictions introduced x March 2003 – Emergency Stage 3 restrictions introduced due to water quality problems arising from rainfall on bushfire affected catchments x May 2003 – Stage 3 restrictions eased to Stage 2 restrictions x July 2005 – Stage 2 restrictions lifted

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x 18 December 2006 – Stage 2 restrictions introduced x 20 February 2007 – Stage 4 restrictions introduced x 29 June 2007 – Water restrictions removed

Water restrictions have not been in place at Swifts Creek since late June 2007.

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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 Swifts Creek, SKM (2006) x Water Supply Demand Strategy, SKM (2007)

The reports are summarised in the following sections.

3.1.1 Drought Response Plan for Swifts Creek (SKM, 2006) Under section 78B and 78C of the Water Industry Act (1994) all corporations holding a retail water licence are required to develop a Drought Response Plan (DRP) for approval by the Minister. The DRP for Swifts Creek 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 Swifts Creek’s water supply system which 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.

3.2 Regulations and Legislation Victoria’s water resources are governed by a number of regulations and legislation. Some key legislation concerning this WSDS is detailed as follows.

Surface Water Caps Each Surface Water Management Area (SWMA) within Victoria is subject to a surface water cap. Swifts Creek falls within Tambo River SWMA which was listed as being slightly modified during a 2005 assessment. The Tambo River basin is capped at current diversions which are roughly equivalent to 7818 ML. A further 2000ML is available for winterfill, although the allocation method for this water is yet to be determined; this decision is currently with the Water Minister. 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).

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 4. 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.

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x Unincorporated Areas (UA’s) – these cover aquifers where groundwater is expected to provide little potential due to low yields or poor water quality.

Swifts Creek is located within an Unincorporated Area therefore no caps on groundwater use have been established.

Figure 4: Groundwater Management Units in East Gippsland (Red: WSPA, Blue: GMA, Orange: UA)

(Source http://gmu.geomatic.com.au/Default.aspx)

Streamflow Management Plans Streamflow Management Plans (SMP’s) 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. No SMP’s have been prepared for waterways in the Tambo Basin (including the Tambo River).

Regional River Health Strategy Stream value for the Tambo River, which supplies Swifts Creek, is covered by the East Gippsland Catchment Management Authority Regional River Health Strategy (EGCMA RRHS). The Tambo River slightly upstream of Swifts Creek is classified as being in ‘marginal’ condition within the RRHS, a target of achieving ‘good’ condition by the end of 2010 was set. The RRHS sets out a number of actions to improve the condition of streams identified as requiring improvements. The upper reaches of the Tambo River at Swifts Creek are also classed as being of high social and economic value, although no targets have been set.

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.

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The Tambo River does not fall under the Heritage Rivers classification, and is therefore not subject to any of the above limitations under the HRA.

Victorian River Health Strategy The Victorian River Health Strategy (VRHS) 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). The Tambo River is subject to those policies set out within the VRHS.

Legislation 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

4.1 Current Demand 4.1.1 Previous Demand Estimates The 2006 DRP presented detailed demand forecasts based on historical average annual diversion rates using demand data from July 2003 to June 2005. The demands outlined in the DRP are shown in Table 2. In relation to these demand estimates SKM (2006) stated that: “The long term average annual diversion from Swifts Creek was estimated to be around 80 ML per year, but there is a high degree of uncertainty in this estimate” This uncertainty was largely due to the fact that Swifts Creek was on Stage 2 water restrictions during the period when data was collected (July 2003 to June 2005) therefore demand was somewhat restricted. The only other data available (1997/98 and 1996/97) showed high demands of between 80 and 120 ML which was likely to be due to the operation of the sawmill which now has its own water supply.

Table 2: Monthly Water Demand (based upon the DRP - SKM, 2006) Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Total Monthly Demand 4.1 4.4 5.0 6.3 7.3 9.1 10.4 9.5 8.8 6.3 5.0 4.0 80.0 (ML) % of Annual 5.1 5.5 6.2 7.8 9.1 11.3 13.0 11.8 11.0 7.9 6.2 5.1 100 Demand Unrestrictable 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 42.5 Demand (ML) 1 Restrictable 0.5 0.8 1.5 2.7 3.7 5.5 6.8 5.9 5.2 2.8 1.4 0.5 37.5 Demand (ML) 1 1 Figures have been rounded therefore may not add up to total monthly demand

4.1.2 Bulk water meter data and historical diversions To assist with establishing an appropriate demand profile for Swifts Creek recent bulk meter data was extracted from EGW’s SCADA system. The volume of bulk water diverted and treated for the last three years is shown in Table 3.

Table 3: Bulk Water Meter Data Meter Readings (ML) 06-07 07-08 08-09 Basin Inlet Meter 31.91 42.6 36.9 Town Water Meter 36.4 39.3 31.2 1 The basin inlet meter was not operational between the 12th June and the 24th of August 2007; this is likely to account for the higher reading at the town water meter during the 2006/07 period.

From Table 3 it can be seen that the average volume of water recorded at the town water meter over the three years was 35.6 ML. The previous WSDS (2007) estimated the long term average demand as 80 ML/annum which is significantly higher than the volume of water extracted over the last three years. Review of bulk water meter data indicates that there was a loss of 5.7 ML between the basin inlet meter and the town water meter (during 08/09). The losses within the reticulation system appear to be negligible with the town water meter having the same reading as the customer billing records. The historical diversions from the Tambo River dating back to 1996 can be seen in Figure 5. It should be noted that diversion figures between 1996 and 2005 are only estimates that have been based on Figure 14-4 of the previous WSDS (SKM, 2007).

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Increase in Sawmill Closed diversions due to 2003 bushfire event

Sawmill re-opened with private supply

Figure 5: Historical Diversions from the Tambo River at Swifts Creek (96/97 FY to 08/09 FY)

From Figure 5 it can be seen that there was a significant drop in the volume of diversions between the 98/99 financial year and the 2000/01 FY. During 1998/99 the sawmill was in full operation and is believed to have been supplied with water from the Swifts Creek water supply system. The sawmill closed during 2000, which is likely to account for the significant reduction in demand during the 99/00 financial year. The sawmill was purchased and re-commissioned by Dormit Pty Ltd during 2001. Discussions with Dormit indicate that when they took over the sawmill they installed two groundwater bores to reduce reliance on mains supply and to provide supply for operations. This has resulted in a significant reduction in annual demand. Since 2001 the diversions at Swifts Creek have been relatively consistent with an average annual diversion of around 37 ML. This excludes the 02/03 financial year when diversions were increased presumably due to bushfires.

4.1.3 Water Consumption and Connections Data EGW has provided water consumption and connection data for the Swifts Creek Water Supply System to assist with determining residential per capita water use. A summary of data provided by EGW is shown in Table 4.

Table 4: Water Consumption and Connection Data

06/07 FY 07/08FY 08/09FY Residential Connections 98 104 103 Non Residential Connections 31 24 25 Total Connections 129 128 128 Residential Demand (ML) 16.4 19.8 18.5 Non Residential Demand (ML) 8.0 9.0 13.1 Total Demand (ML) 24.4 28.8 31.6 Residential Water Use (L/capita/day)1 202.9 230.8 217.7 1 Calculating assuming an average residential occupancy of 2.26 persons per home

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4.1.4 Industrial/Commercial Water Use Review of the data provided in Table 4 shows that on average 35% of water is used for commercial/industrial purposes and 65% is used for residential purposes. Based on the previous WSDS (2007), it would seem that there has been a slight increase in water demand in the residential sector and a slight decrease in the commercial/industrial sector. This may be attributed to the increasing population. Review of customer billing data for the 2008/09 financial year shows that the highest volume water user (located on the Great Alpine Road) used 3.2 ML during the last financial year. This is roughly equivalent to 10% of the towns total water use. The five top non residential water users accounted for 8.4 ML of water used during the 08/09 period which is equivalent to 27% of the total water demand.

4.1.5 Unaccounted Water Unaccounted water represents the difference between bulk water sourced from the Tambo River and overall water consumption plus any accounted water not billed by EGW. It includes items such as water lost though leakage due to pipe breaks, process water and any other water not calculated. Unaccounted water for the last three years as determined by EGW is shown in Table 5.

Table 5: Unaccounted Water (EGW, 2009)

06/07 FY 07/08FY 08/09FY Volume Unaccounted (ML) 10.6 9.8 4.4 Percentage of Total Volume Diverted (%) N/A1 23% 12% 1 Percentage cannot be accurately determined as the bulk water meter was not operational for a significant part of the year

In the previous WSDS (SKM, 2007) it was reported that there was no unaccounted water in the Swifts Creek water supply system during 2004/05. It was noted and also recommended that the losses in the system be monitored after construction of the new treatment plant which occurred during July of 2008. From Table 5 it can be seen that the volume of unaccounted water significantly reduced after the construction of the water treatment plant. The volume of unaccounted water during the last financial year (08/09) was 12%. This is slightly higher than the losses across EGW’s entire area of service, which was reported as 8.5% in their 2008/09 Annual Report. The target set in EGW’s Water Plan is to reduce unaccounted water to 10%. It is therefore recommended that EGW continue to monitor and reduce losses within the water supply system.

4.1.6 Summary of Current Demand SKM (2007) reported the long term average annual demand at Swifts Creek as 80ML/annum. This was likely to account for the significant demand at the old saw mill which is no longer supplied under Swifts Creek’s bulk entitlement. Given that Swifts Creek hasn’t been on water restrictions since 2007 and the water demand has remained relatively consistent over the last nine years (with the exception of 2003 where there was a significant bushfire event) the long term average annual demand can be estimated as 40ML.

4.2 Forecast Water Demand

4.2.1 Previous Population Projections In the previous WSDS prepared by SKM (2007), both available census data and Victoria in Future population projections were used for estimating future population. The WSDS assumed a 67% decline in population between 2005 and 2055. The magnitude of this decline seems to be unreasonable given that this would see the population fall from over 280 people to less than 100 people over the next 50 years.

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4.2.2 Recent Census Data The 2007 WSDS identified the need to review 2006 census data (which was unavailable at the time) to confirm population trends and particularly whether or not the predicted decline in population was reasonable. The 2006 Census data has now been released and is compared to the 2001 and 1996 Census data results in Table 6.

Table 6: Census Population Data 1996 Census 2001 Census 2006 Census Population 228 164 281 Total Dwellings N/A 97 176

Based on the data presented in Table 6 it could be concluded that the population in Swifts Creek over the last 10 years has been extremely variable. It is more likely that the data collected/recorded during 2001 was not representative. The Australian Bureau of Statistics (ABS) was contacted on the 14 Jan 2010 to confirm the accuracy of the 2001 statistic however they were unable to provide any further advice. Discussions with East Gippsland Shire Council (EGSC) indicate that the 2001 census was based on a three collection districts while the 1996 and 2006 census were based upon two collection districts. This means that a different area was sampled during 2001. This is likely to account for the reported increase in population between 2001 and 2006. It is therefore more appropriate to compare like with like and consider only the 1996 and 2006 census figures. Based on the change in population between 1996 and 2006, there has been growth at a rate of 2.1% per annum. Discussions with EGSC indicate that this growth rate is not likely to be representative of future growth in Swifts Creek. It was also advised that the town has limited opportunity for development as properties within the township zone are bounded by larger farming type properties which are unlikely to be sub-divided. Based on these discussions, the growth rate of 2.1% per annum will not be considered further for estimating the future population at Swifts Creek.

4.2.3 Victoria in Future Data The Victoria in Future (VIF) population projections for 2008 suggest an overall increase in population throughout the East Gippsland Region. As Swifts Creek is not a major urban centre, the expected population increase is best predicted using the statistical balance (the balance of all those areas outside of major urban centres). The 2008 VIF data suggests a 12.4% increase in population for the statistical balance over a period of 20 years (between 2006 and 2026); this is equivalent to a growth rate of approximately 0.6% per annum. This is much higher than the figures reported in the previous release of VIF (2006) which suggested a decrease of between 1.5% to 2.5% (SKM, 2007). The wider projections for regional Victoria show a predicted increase of 1.18% per annum between 2006 and 2026 and 0.78% per annum between 2026 and 2056. These predictions are much higher than those made for the balance of the statistical area (0.6% p/a). Given that the statistical balance is likely to be more appropriate for estimating future population in Swifts Creek, it is proposed to adopt a growth rate of 0.6% per annum between 2006 and 2026, and a reduced rate of 0.5% per annum between 2026 and 2060 (this reduced rate has been estimated based on longer range VIF data). This results in an overall population increase of approximately 95 people. EGSC has advised that they are not expecting significant growth at Swifts Creek and an increase of 0.6% p/a would be a reasonable assumption. This approach would be slightly conservative given that Council is expecting the population to remain relatively stable.

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5.0 Demand Management and Reduction

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. East Gippsland Water is part of the savewater!TM alliance through the Victorian Water Industry Association, which represents all of Victoria’s water corporations. 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 corporation 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 Swifts Creek. 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. The above paragraph is written in the context of all of EGW’s supply systems which include coastal towns such as Lakes Entrance. The average daily per capita demand has been estimated based on customer billing data, recent census data and VIF population projections. From this information the average daily water use is 217L/day per person (based on available data). It is expected that this estimate of demand would be relatively accurate given that Swifts Creek is not known to have large visitor numbers during peak periods. 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 corporations 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

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x The State Government will reform the water component of the 5-star building standard to make it performance based. 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. 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 Swifts Creek’s water supply system relating to climate change is a significant reduction in the volume of surface water available for extraction from the Tambo 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 streamflow 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 streamflow reduction figures for the Omeo WSDS (2010). The key difference between these reports is that the SEACI report uses only a medium emissions scenario to formulate runoff scenarios, while the CSIRO report also considered a high and low scenario. The SEACI report has been adopted for input into the WSDS as it specifically covers the area of Swifts Creek while the CSIRO report does not. The percentage change in modelled mean annual run off for Swifts Creek (~2030 relative to 1990) based on SEACI modelling is projected to be -11.4% for the median scenario and -27.2% for the dry scenario. The dry scenario has been selected as the most prudent scenario (i.e. a -27.2% 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. The previous WSDS (SKM, 2007) stated that: “Based on advice from the Department of Sustainability and Environment (2005), demands are expected to increase by around 1% by the year 2055 for every 6% reduction in streamflow” This would result in an increase in demand of approximately 4.5% (or 1.8ML/annum) by 2055. EGW has a target for an 8% reduction in per capita demand by 2020. It is highly likely that with ongoing demand reduction initiatives, EGW customers will continue to become more efficient with their water use and as a result it’s been assumed that the increase in demand associated with climate change will be offset by more efficient water use. 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.

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Streamflow gauging on the Tambo River has been relatively consistent since its commencement in 1958. It is difficult to evaluate whether or not step climate change has impacted flows in the Tambo River due to the increases in streamflow that can be attributed to the 2003 bushfires. When considering the 10 years of flow data prior to 2003 the reduction in streamflow when compared to the historical record is around 26%. This is less than the dry climate change scenario, therefore for this investigation the dry climate change scenario from the SEACI report (-27.2%) has been adopted for modelling purposes.

6.2 Impact of Bushfires 6.2.1 Background Bushfires in forested catchments have the potential to significantly impact runoff and therefore streamflows over time. The upper reaches of the Tambo River catchment is largely native forest, with extensive farming areas immediately north of Swifts Creek.

6.2.2 Previous Bushfires SKM (2009) reported that the 2003 bushfire burnt approximately 77% of their study catchment; this is roughly equivalent to 80% of the catchment upstream of Swifts Creek. Runoff after bushfires initially increases in the first few years until vegetation starts to re-grow, whereupon runoff starts to decrease. This impact is demonstrated by the streamflow response curve presented in Figure 6 below. The curve details predicted changes in streamflow resulting from the 2003 bushfires for the Tambo River catchment within which Swifts Creek resides.

Figure 6: Estimated reduction in streamflow in the Tambo River due to the 2003 bushfire (SKM, 2009)

The curve in Figure 6 suggests the catchment is yet to experience the projected decrease in streamflow and that the maximum reduction in streamflow will not occur until around 2030. Beyond this time period, streamflows will gradually return to pre-bushfire levels as the new forest matures unless the catchment burns again. Streamflow reductions for a number of time-steps are interpolated from Figure 6 as follows: x The current impact of the 2003 bushfires in terms of changes to streamflow is negligible (i.e. 0% change) x At 2030 it is expected that the reduction in streamflow associated with the bushfires will be around 15% x At 2060 the expected reduction in streamflow associated with the bushfires will be around 10%.

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From review of available information it has been estimated that around 80% of the Swifts Creek catchment was burnt by the 2003 fires, therefore to estimate the impact of streamflow reductions due to bushfire, the percentage of the catchment burnt has been multiplied with the percentage reduction in streamflow (as this is across the entire catchment). Discussions with DSE and review of SKM’s bushfire report (2009) have provided an appreciation for the complexity of the interactions between climate change and the impacts associated with bushfires. SKM (2009) stated that: “… the impact of climate change on water resource yield is likely to interact with the expected response following a bushfire such that the two processes may not be independently identifiable. It is not clear how the interaction of the bushfire and climate change impacts on climate change will play out into the future”. DSE has advised that the percentage reductions in streamflow resulting from forest regrowth after a bushfire would be lessened in a drier climate. To account for the lessened impact a 50% reduction (15% to 7.5% in 2030) in the magnitude of bushfire impacts was modelled when using the high climate change scenario.

6.2.3 Future Bushfires The GRSWS (2009) stated that: “The Gippsland Region has been subject to three severe bushfire events in the past decade. Under climate change, it is likely that bushfires will become more frequent, intense and extensive”. While it is likely that the frequency of bushfires will increase into the future, this WSDS has only considered past bushfires as the impacts have been quantified and assessed.

6.2.4 Proposed Fuel Reduction DSE is proposing to undertake fuel reduction burns over the next 3 years that will impact on 26% of the Swifts Creek catchment. EGW has agreed that this approach is reasonable although have requested that the fuel reduction be done by “cool” burning as it will have a lesser impact on runoff than a bushfire. EGW has also requested that canopy burns within the catchment be minimised. 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.

6.3 Forestry Areas within the Tambo 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 off-take would be relatively small, provided the logging remains dispersed across the catchment (SKM, 2007). To ensure reliability of supply it is recommended that EGW continue to monitor the impacts of logging. If long term security begins to diminish, then a reduction in the area to be logged within the water supply catchment should be sought.

6.4 Future Streamflow Projections The effect of potential climate change and bushfire impacts on future streamflow is demonstrated in Figure 7.

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Figure 7: Future Streamflow Projections

Note: Each streamflow projection is plotted exclusive of the impacts of other variables and uncertainties

From Figure 7 it can be seen that the impacts of bushfire and climate change under the worst case scenario (Dry climate change and a 15% reduction in streamflow due to bushfire) will have a significant impact on future streamflow availability.

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7.0 Reliability of Supply 7.1.1 Method Overview The method adopted for the REALM modelling can be summarised as: x Review previous SKM model and identify any issues; x Collate streamflow data and update where possible; x Undertake preliminary modelling (current situation); x Set restriction triggers; and x Undertake further modelling and produce output graphs.

7.1.2 Modelling Assumptions Streamflow Data x Data from gauging station 223202C (Tambo River @ Swifts Creek) has been selected over data from gauging station 223208A (Tambo River @ Bindi near Junction Creek) as flow monitoring at Swifts Creek has been relatively continuous from 1947 to 2009 while flow records at Bindi have a much shorter duration starting at 1971 and ending in 2001. The Swifts Creek gauging station provides a more conservative approach because of its location downstream of the town water off-take. x Private diversions have not been considered in the model as a total ban would be placed on all upstream users when the flow is reduced to less than 4 ML/day, it is therefore reasonable to assume that EGW will not be impacted by upstream diversions as the maximum rate that EGW can extract water at is 1.1 ML/day.

Demand Data x The demands within the previous model have been revised based on the latest available data. The revised demand is 40 ML/annum with the same seasonal pattern as was used by SKM previously. x For the future (2060) scenario an increased demand figure was used. The rate of growth was 0.6% per annum between 2006 and 2026 and 0.5% per annum between 2026 and 2060. It was assumed that population and demand are linearly linked. The base year for determining the population growth was 2010. x The reductions in demand due to the onset of restrictions is as follows (based on EGW water restriction by- laws): Stage of Restriction Annual Reduction of Total Demand (%) One 2.5 Two 8 Three 12 Four 17.5

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. This assumption will need to be reviewed upon release of updated climate change information. x The reduction in streamflow will occur in a linear fashion, reducing by a fixed amount each year between 1990 and 2030 x The increase in demand associated with climate change (4.5% or 1.8 ML/annum) will be negligible when considering further development in water efficiency.

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REALM Model x The previous REALM model for Swifts Creek was developed based on a monthly time step. This was changed to a weekly time step to provide improved accuracy in modelling results. Using a weekly time step model is considered a significant improvement when compared to using a monthly time step.

7.2 Current Reliability of Supply The existing system (which includes 4.6ML of off-stream storage) 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 40ML and a 27.2% reduction on historical streamflows resulting from the dry climate change scenario (~2030 relative to 1990). Bushfire impacts were considered to be minor at this point in time as 2010 is very close to the transition point of the initial streamflow increase and future streamflow decrease. The current restriction triggers as stated within the DRP (SKM, 2006) were adopted for modelling the current situation; these triggers are shown as follows: x Voluntary – Streamflow = 15ML/day x Stage 2 – Streamflow = 5ML/day x Stage 4 – Storage = 2ML

The current situation model (2010) is shown in Figure 8 as follows.

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Figure 8: Current Reliability of Supply

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Figure 8 shows that under current arrangements voluntary restrictions would be required on average once in every 3 years and Stage 2 restrictions would be required once in every 4 years. This is significantly more frequent that EGW’s LOS objectives of Stage 2 restrictions being required no more frequently than once every 10 years. With further reductions in streamflow expected to occur over the next 20 years it expected that it will become increasing difficult to meet LOS objectives under current arrangements. The current situation (2010) model also provides an overview of the storage volume over time which is presented in Figure 9.

Figure 9: Reservoir Storage Levels (Current Situation)

Both Voluntary and Stage 1 triggers are currently based upon streamflow and as a result the storage rarely draws down, yet restrictions are triggered frequently as demonstrated in Figure 8 and Figure 9. Throughout the historical record there has only been one instance when the storage has been significantly drawn down. On this occasion the storage volume was reduced to around 1 ML (from 4.6 ML). Based on modelling of the current situation it can be concluded that Swifts Creek’s water supply system is very reliable although revision of the restriction triggers is required to ensure that LOS objectives are met in the future.

7.3 Future Reliability of Supply To assess EGW’s ability to meet LOS objectives in the future (2060) a second run of the REALM model was undertaken. The dry climate change scenario (27.2%) was adopted to be consistent with recent scientific studies that suggest that climate change has been tracking along the worst case of the previously modelled scenarios. A 50% reduction (from 10% to 5% in 2060) in the magnitude of the bushfire impacts was adopted given advice from DSE that the percentage reductions in streamflow resulting from forest regrowth after a bushfire would be lessened in a drier climate (refer Section 6.2 for further discussion). A sensitivity analysis was also undertaken on the percentage reduction in bushfire impacts (due to a drier climate) although this had minimal impact on reliability of supply.

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The future modelling scenario is summarised as follows:

Table 7: Modelling Scenario (2060) Modelling Parameter Adopted Value Climate Change Reduction in Streamflow (2060) -27.2% Bushfire Reduction in Streamflow (2060) -5% Growth Predictions (per annum) 0.6% (2006 to 2026) and 0.5% (2027 to 2060)

Table 8: Previous and Revised Restriction Triggers Level of Restriction Previous Triggers Revised Triggers Voluntary Streamflow = 15ML/day Streamflow = 2ML/day Stage 2 Streamflow = 5ML/day Storage = 4ML Stage 4 Storage = 2ML Storage = 1.5ML

The results can be seen in Figure 10 (refer next page). These above restriction triggers provide the following response times and service levels:

Table 9: Response times and service levels for revised restriction triggers Level of Restriction Remaining Supply Restriction Frequency Voluntary 40 days 1 in 7 years Stage 2 32 days 1 in 32 years Stage 4 14 days 1 in 62 years

The time between Voluntary and Stage 2 restrictions based on the streamflow recession curve prepared by SKM, 2006 is approximately 8 days (assuming no rainfall). A further 18 days of storage is provided between the commencement of Stage 2 and Stage 4 restrictions (during the peak month assuming no rainfall). It can be seen from Table 9 that the restriction frequencies are well within EGW’s LOS objectives.

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Figure 10: Future Reliability of Supply with Revised Restriction Triggers

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The volume of storage for the second model run can be seen in Figure 11.

Figure 11: Reservoir Storage Levels (Current Situation)

It can be seen from Figure 11 that under the revised restriction triggers given the reduced streamflow associated with climate change and bushfires, the storage only experiences significant draw down on one occasion during the historical record. On this occasion the storage runs empty. The model does not allow for alternative supply during times of shortage (i.e. groundwater) therefore this draw down could be managed by providing an alternative water supply.

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8.0 Options for Managing Water Supply REALM modelling of the Swifts Creek water supply system has shown that the Tambo River is very reliable in providing the required volume of water to the town. Under reduced streamflow conditions (due to climate change and bushfires), supply to the town can be managed with current infrastructure, although a change to restriction triggers would be required to ensure that EGW’s LOS objectives are met. Throughout the historical record (62 years) there was only one event during which supply to the town was compromised (2007). During this event an alternative water source would have been required to supplement the storage. The following section of this report details a number of options that EGW should consider for managing water supply during times of drought/shortage.

8.1 Groundwater Groundwater bore (95742) could be used to supplement surface water supplies during times of drought. In the past water from the bore has been pumped by installing a temporary pipeline which runs through a culvert into an existing transfer pump station. The water is then transported to the storage basin and is mixed with the diverted surface waters to provide an increased volume of water. It has been reported by SKM (2007) that the capacity of this bore is 0.11 ML/d (1.3 L/sec) although discussions with operations staff indicate that this bore is relatively low yielding with a small flow rate and an available pumping time of around half an hour (with a half hour recovery time). The yield from the bore is estimated at around 0.05 ML/day. Operations staff have advised that the quality of the groundwater is roughly equivalent to that of the surface water therefore the use of groundwater should not result in treatment plant performance issues. The location of the bore in relation to other infrastructure is shown in Figure 2.

8.2 Water Loss Reduction Data provided in Figure 5 indicates that during the last financial year approximately 4.4ML (or 12% of total water diverted) was lost within the system. Preliminary analysis has been undertaken to determine the impact of leakage reduction within the system on securing Swifts Creek’s water supply. This analysis has shown that reducing the level of leakage to the widely accepted value of 10% will not significantly improve water security for Swifts Creek providing only a minor increase in the volume of water available during periods when the storage is progressively drawn down. Despite this, EGW should investigate the cause for the high losses and implement any remedial measures deemed to be cost effective.

8.3 Water Carting Water carting should only be considered as an emergency supply in the event that Swifts Creek’s water storage approaches critically low levels or when quality of supply from the Tambo River is compromised (e.g. due to bushfires). Based on modelling, water carting should be required infrequently (no more than 1 in 60 years) and therefore is financially viable compared to investing in large infrastructure that may be used infrequently or not at all. From discussions with EGW it is understood that they have previously held emergency water carting agreements with the NECMA for supply of bulk water from the Mitta Mitta River. Preliminary discussions with the NECMA indicate that this supply could be formalised into EGW’s existing bulk entitlement for use in future emergency situations. However, it should be noted that the Mitta Mitta River is subject to strict caps on diversions therefore availability of supply may not be guaranteed. In the event that water is not available in the Mitta Mitta River, alternative water supply sources should be sought (i.e. supply from other nearby towns).

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8.4 Recommendations for Managing Supply A number of options have been identified to improve the operation of Swifts Creek’s water supply system. It is recommended that EGW: x Revise their restriction triggers so that LOS objectives can be met; x Continue to monitor and strive to reduce losses within the water supply system; x Use the groundwater bore to supplement surface water flows during times of drought/water shortage; x In times of emergency, cart water from the Mitta Mitta River or another alternative supply system.

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9.0 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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10.0 Conclusions and Recommendations REALM modelling of the Swifts Creek water supply system has shown that the Tambo River is very reliable in satisfying the water demand of the town. During the historical record of 62 years there has only been one event during which the storage basin at Swifts Creek was significantly depleted, this occurred during 2007. Modelling has shown that under current arrangements with the impacts of climate change, bushfires and growth, restrictions will be triggered more frequently than required by EGW’s LOS objectives. Modelling has shown that with the optimisation of the current restriction triggers, LOS objectives can be met both now and into the future without the construction of additional infrastructure. It is therefore concluded that available supply at Swifts Creek should exceed demand over the next 50 years even when considering the impacts of climate change, past bushfires and growth in water demand. As a result, further supply enhancement will not be required. To ensure ongoing reliability of supply it is recommended that EGW: x Implement the recommendations for managing supply (Section 8.4); x Continue to monitor the impacts of logging and if a long term supply shortage is anticipated seek a reduction in the area to be logged within the water supply catchment; x Formalise emergency access to the Mitta Mitta River for water carting into the existing bulk entitlement; x Update Swifts Creek’s Drought Response Plan.

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11.0 References AECOM, (2010) Omeo Water Supply Demand Strategy

Chiew, F., Vaze, J., Viney, N., Jordan, P., Perraud, J-M., Zang, L., Teng, J., Arancibia, J A., Morden, R., Freebairn, A., Austin, J., Hill, P., Wiesemfeld C., and Murphy, R. (2008) Rainfall-runoff modelling across the Murray-Darling Basin A report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project

CSIRO, (2008) Rainfall-runoff modelling across the Murray-Darling Basin

DSE, (2005) Guidelines for the Development of a Water Supply Demand Strategy

DSE, (2009) Gippsland Region Sustainable Water Strategy – Discussion Paper

Environment Victoria, (2009) http://www.envict.org.au/inform.php?menu=7&submenu=220&item=668

Lane, P., Sheridan, G., Noske, P., Costenaro, J., Sherwin, C., Szegedy, G and McKenna, P (2009). Dynamics of sediment and nutrient fluxes from burnt forest catchments. Final Report prepared for Land & Water Australia.

Lane, P., Sherwin, C., Peel, M., Freebairn, A. (2007) Impact of the 2003 Alpine Bushfires on Streamflow - Predicting the long-term impacts of bushfire on water yield. Report for the Murray-Darling Basin Commission and the Department of Sustainability and Environment.

Rahmstorf et al, (2007) Recent Climate Observations Compared to Projections. Science 316, 1.

South Eastern Australian Climate Initiative, (2008) Future Runoff Projections (~2030) for South East Australia

SKM, (2009) Combined impact of the 2003 and 2006/07 bushfires on streamflow - Broadscale Assessment

SKM, (2007) East Gippsland Water: Water Supply Demand Strategy

SKM, (2006) East Gippsland Water: Drought Response Plan – Omeo, Dinners Plain and Swifts Creek

SRW, (2009) http://www.srw.com.au/Files/Local_management_rules/tambo_local_Management_Rules_Sept09.pdf

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