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East Gippsland Water

15 March 2010

Omeo Water Supply Demand Strategy

AECOMOmeo Water Supply Demand Strategy

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Omeo 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

15 March 2010

60049414

© AECOM Australia Pty Ltd 2010

The information contained in this document produced by AECOM Australia Pty Ltd is solely for the use of the Client identified on the cover sheet for the purpose for which it has been prepared and AECOM Australia Pty Ltd undertakes no duty to or accepts any responsibility to any third party who may rely upon this document.

All rights reserved. No section or element of this document may be removed from this document, reproduced, electronically stored or transmitted in any form without the written permission of AECOM Australia Pty Ltd.


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Quality Information

Document Omeo Water Supply Demand Strategy

Ref 60049414

Date 15 March 2010

Prepared by Mandy Habener / Steven Wallner

Reviewed by Andrew Grant

Revision History

RevisionRevisionDate

DetailsAuthorised

Name/Position Signature

A 03-Aug-2009 For Review Andrew Grant Original Signed

B 04-Sep-2009 Final Andrew Grant Original Signed

C 14-Oct-2009 Revised Final Andrew Grant Original Signed

D 15-Mar-2010 2nd Revised Final Andrew Grant Original Signed



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 Groundwater Licences 5

2.3 Level of Service Objectives 5 2.4 Historical Water Restrictions 5

3.0 Previous Studies, Legislation and Regulation 6 3.1 Previous Long Term Planning Studies 6 3.2 Regulations and Legislation 6

4.0 Water Demand 9 4.1 Current Demand 9

4.1.1 Summary of Current Demand 10 4.2 Forecasted Water Demand 10

4.2.1 Previous Population Projections 10 4.2.2 Recent Census Data 10 4.2.3 Victoria in Future Data 11 4.2.4 East Gippsland Shire Council 11 4.2.5 Adopted Trends 11 4.2.6 Commercial and Industrial Water Use 11

4.3 Summary of Demand Projections 12 5.0 Demand Management and Reduction 13

5.1 Measures to Achieve Demand Reduction Targets 13 5.1.1 Current Demand Reduction Initiatives (SKM, 2007) 13 5.1.2 Future Demand Reduction Initiatives (SKM, 2007) 14

6.0 Water Supply 16 6.1 Impact of Climate Change 16 6.2 Impact of Bushfires 17

6.2.1 Background 17 6.3 Forestry 18 6.4 Future Streamflow Projections 19

7.0 Reliability of Supply 20 7.1 REALM Modelling Method 20

7.1.1 Method Overview 20 7.1.2 Modelling Assumptions 20

7.2 Current Reliability of Supply 21 7.3 Future Reliability of Supply 23

7.3.1 Future Supply and Demand Scenarios 23 7.3.2 Setting Restriction Triggers 24 7.3.3 Summary of Future Reliability of Supply 24

8.0 Alternative Supply Options 27 8.1 Surface Water 27 8.2 Groundwater 29 8.3 Water Loss Reduction 30 8.4 Recycled Water (from the Omeo WWTP) 30 8.5 Rainwater 31 8.6 Stormwater 31 8.7 Water Carting 32 8.8 Options to Considered Further 32

9.0 Assessment of Supply Options 33 9.1 Multi Criteria Analysis (MCA) 33

9.1.1 Selection of Criteria 33



9.1.2 Weightings 33 9.1.3 Results 34 9.1.4 Discussion 36

9.2 Expected Scheme Costs 36 10.0 Stakeholder Consultation 37 11.0 Conclusions and Recommendations 38

11.1 Conclusion 38 11.2 Summary of Recommendations 38

12.0 References 39

Appendix A REALM Modelling Results ....................................................................................................................... A

Appendix B Streamflow Reliability Charts ................................................................................................................... B


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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 Omeo water supply system. This revised WSDS will replace the strategy set out for Omeo in EGW’s overall WSDS (Section 12).

EGW has set level of service (LOS) objectives for water supply reliability. The objectives state that:

Moderate restrictions (Stages 1 & 2) are not desired more frequently on average than 1 year in 10; and

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 Omeo’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 regards to EGW’s LOS objectives. The assessment showed that Stage 2 restrictions would be required on average once every 4 years. This is significantly more frequent that EGW’s LOS objective of restrictions being required no more frequent than once every 10 years. It was therefore concluded that Omeo’s current water supply system in insufficient.

To gain an understanding of how security of supply in Omeo is likely to change with the impacts of climate change, bushfire impacts and population growth, three scenarios were developed. These scenarios were also used to determine how much additional storage Omeo would require to meet EGW’s LOS objectives. The scenarios modelled are summarised as follows.

Table E1: Summary of REALM Modelling Scenarios

Scenario Reduction in Streamflow from Climate Change

Reduction in Streamflow from Bushfires1

Population growth

S1 – High Impact 37% 11% Stagnant S2 – Moderate Impact 10% 5.5% 1.5% decline S3 - Intermediate 37% 5.5% Stagnant 1 Reduction only applied across 38% of catchment that was burnt

The modelling results are summarised in the following table.

Table E2: Summary of Modelling Results

Drawdown to stage 1 restrictions

Total storage required1

Frequency of stage 3/4 restrictions

Reservoir depletion at onset of stage 1 restrictions

Frequency of reservoir failure

Scenario 1 (2030) 8ML 15ML 1 in 100 50% 1 in 100 Scenario 2 (2009) 4.5ML 12.5ML 1 in 100 35% 1 in 100 Scenario 2 (2030) 2ML 10ML – 6ML2 1 in 100 35% 1 in 100 Scenario 3 (2030 – stagnant population)

7.5ML 15ML 1 in 100 50% 1 in 100

Scenario 3 (2030 – declining population)

3ML 11ML - 7ML2 1 in 100 27% 1 in 100

1 (includes 5 ML existing storage)

2 Due to the reduced rate of drawdown it may be appropriate to reduce the buffer between restrictions from 3ML to 2ML or even

1ML.


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The results from modelling confirmed that population growth and climate change have a much larger impact on storage requirements than bushfire impacts. In determining the optimum size for a new storage it is recommended that EGW adopt planning Scenario 3 (stagnant population) and construct a new 10ML storage which would give 15ML of storage in total. The estimated cost to construct an additional 10 ML of bulk storage is $600,000.

To ensure that the construction of additional storage is an appropriate option, a number of alternative water supply options were identified and assessed using a Multi Criteria Analysis (MCA).

The options identified are listed in the following table along with some comments regarding their feasibility/suitability for supplying Omeo.

Table E3: Feasibility of Alternative Supplies

Option Comments Surface water supply from Livingstone Creek

Difficult to gain access to low flows. Considered as the most cost effective alternative surface water supply.

Surface water supply from Mitta Mitta River

Not considered in the MCA due to the significant distance and the likely cost of infrastructure.

Surface water supply from Victoria River

Not considered in the MCA as it is less reliable than the Livingstone Creek and is further away.

Surface water supply from Wentworth River (via Jirnkee water race)

Not considered in the MCA due to the significant cost of a new pipeline, difficulty of construction and likely political and environmental issues associated in transferring water between catchments.

Water Carting (from Mitta Mitta River)

Found to be a suitable emergency supply for Omeo.

Demand Management and Reduction of Water losses

Will not significantly improve the security of Omeo’s water supply, but should be considered as part of an integrated strategy.

Groundwater Treatment and Delivery

Bores within township are high in salt and would require treatment for bulk supply. Bores outside town with higher water quality would require long pipelines. Both options not considered in MCA due to excessive cost.

Groundwater Blending and Carting

Carting from groundwater bores for blending with raw water was found to be a suitable emergency supply alternative for Omeo.

Recycled Water (third pipe/customer re-use)

Considered as a potential alternative although given the limited opportunities for reuse and the high capital expenditure this option did not rank highly

Rainwater Not considered in the MCA as the cost of retrofitting rainwater tanks to achieve only a 15% reduction in demand is high and rainwater tanks will make little difference to unrestrictable demand.

Stormwater Not considered in the MCA as it is unlikely to provide significant supply during critical water supply periods.

The proposed scheme to improve reliability of supply to Omeo is:

1) Improve reliability of supply by:

a. construction of 10ML additional usable raw water storage and

b. ongoing implementation of cost effective demand management measures

2) Provide emergency supply by:

a. Water carting from either the Mitta Mitta River or nearby groundwater bores

Based on the modelling undertaken and the assessment of options it is recommended that EGW undertake the following to secure Omeo’s water supply:

Continue the current practice of extracting water from Butchers Creek as Omeo’s main source of bulk water supply;


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Construct an additional 10ML of useable raw water storage to complement the existing bulk water storage;

Investigate the feasibility of using the abandoned raw water storage as a site for the additional bulk storage;

Implement and monitor performance of demand management and leakage reduction strategies;

Formalise emergency access to the Mitta Mitta River for water carting into the existing bulk entitlement;

Seek to formalise emergency access to the groundwater bore at the nearby football oval;

Investigate the impacts of using high salinity feedwater at the WTP (in terms of the impact of operation and quality) and

Continue to seek a reduction in the area to be logged within Omeo’s water supply catchment;

Update Omeo’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’s are otherwise required to be reviewed and updated every 5 years.

Continuing dry conditions have resulted in a significant drop in streamflows right across 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’s may over estimate long term yields.

During February of 2009 Butchers Creek (Omeo’s sole water supply source) was reduced to a trickle for a period of around two weeks. On 9 February 2009 Omeo was placed on Voluntary Water Restrictions. Omeo has only limited storage and as such these flow conditions pose a significant threat to the ability of EGW to meet their level of service commitment.

The previous WSDS recommended that an additional 7ML water storage be constructed to meet Omeo’s future water supply requirements. The previous study also identified uncertainties relating to the impacts of bushfires within the Butchers Creek catchment as well as declining population predictions. With the worsening of climatic conditions and the recent availability of updated data relating to bushfire impacts and population, EGW has decided to review the WSDS for Omeo to ensure that future infrastructure investment will meet Omeo’s long term water supply needs.

This document forms a revised WSDS for the Omeo water supply system and will replace the strategy set out for Omeo in EGW’s overall WSDS (Section 12). 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

Omeo is located approximately 80km north of Bairnsdale in the north-west corner of East Gippsland Shire. The township of Omeo is located on the Great Alpine Road, providing easy access to the ski resorts at Mt Hotham and Dinner Plain. Omeo is a relatively small township with a permanent population of around 200.

The location of Omeo is shown in Figure 1 as follows.



Figure 1: Regional Map



2.0 Current Water Supplies

2.1 Description of Water Supply System

Omeo’s water supply is currently sourced from Butchers Creek, a tributary of Livingstone Creek. The catchment area feeding Butchers Creek is approximately 21km2. Diversions from the creek are taken in accordance with EGW’s bulk entitlement (refer to Section 2.2.1 of this report). Raw water is fed either directly to the Water Treatment Plant (WTP) or into a 5ML lined storage basin prior to treatment, this is undertaken via 12km of DN100mm diversion main which has a capacity of 7.5 l/s (approximately 0.65 ML/d).

The Omeo WTP was commissioned in 1995 and was designed to treat 0.6 ML/day. The WTP was upgraded during 2003/2004 to include online monitoring to improve turbidity, aluminium carry-over and disinfection. Treated water from the WTP is sent to a 200kL clear water storage tank prior to distribution to the Omeo Township via a DN150mm main.

Omeo has a single drought relief bore (number 55931) which is reported by SKM (2007) to have a capacity of 1.2 l/s (0.10 ML/d). The bore is said to have a Total Dissolved Solids (TDS) level of 940mg/L which is very close to the limit of 1000mg/L for acceptable taste (SKM, 2006). Due to the high TDS level it was previously concluded that this groundwater bore is unsuitable for use as potable water supply. The location of the bore in relation to other infrastructure is shown in Figure 2.

Figure 2: Groundwater Bore (55931) Location



The Omeo water supply system also has a 7 ML storage which was previously used to store diversions from Livingstone Creek. This storage has now been decommissioned and fully disconnected from the reticulation system as it is located downstream of the WTP. It is possible that this storage could be repaired and restored to service if required.

A schematic of the Omeo supply system is shown in Figure 3 below.

Figure 3: Omeo Water Supply System

2.2 Allocations of Water

2.2.1 Bulk Entitlements

East Gippsland Water has a bulk water entitlement of 77ML per year for Butchers Creek which is subject to the following flow sharing arrangements:

When the flow is less than or equal to 1.3ML/day then EGW’s entitlement is equal to half (0.5x) the daily flow

When the flow is above 1.3ML/day then EGW’s entitlement is 0.66ML/day

This entitlement was outlined in the Victorian Government Gazette on the 12 June 2008; this can be seen at http://www.gazette.vic.gov.au/gazette/Gazettes2008/GG2008G024.pdf.

OMEO

WWTP

WTP

Irrigation

Raw Water

Storage (5ML)

Groundwater Bore Livingstone Creek

Butchers Creek

Streamflow Gauge

(Reinstated June

2009)

Gravity

Diversion Main

0.65ML/day

22 ML/year

200kL Clearwater

Storage



2.2.2 Groundwater Licences

SKM (2006) stated that:

“East Gippsland Water has a groundwater licence for extracting groundwater at Omeo from bore number 55931….”

It is understood that this bore was installed by the Omeo Shire circa 1968 but was never used due to the hardness of the water. The maximum allowable diversion rate from this groundwater bore is unknown.

2.3 Level of Service Objectives

EGW has previously defined the following level of service objectives for water supply reliability:

Moderate restrictions (Stages 1 & 2) are not desired more frequently on average than 1 year in 10; and

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

Omeo is currently subject to Permanent Water Saving Rules (which are being applied as part of a Victoria wide strategy).

2.4 Historical Water Restrictions

A search of EGW’s archives found the following historical events relating to changes in water restrictions for Omeo.

May 2003 - voluntary restrictions removed

February 2007 - Stage 2 restrictions increased to Stage 4

May 2007 - Stage 4 restrictions decreased to Stage 2

June 2007 - Stage 2 restrictions removed

February 2009 - voluntary restrictions invoked

April 2009 - voluntary restrictions removed



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:

Augmentation of Omeo Township Water Supply, Binnie and Partners (1991)

Omeo Water Supply: Butcher Creek Streamflow Analysis, Kinhill Engineers (1993)

Drought Response Plan, SKM (2006)

Water Supply Demand Strategy, SKM (2007)

The most recent reports have been summarised as follows.

EGW Drought Response Plan – Omeo, Dinner Plain and Swifts Creek (2006)

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. This DRP for Omeo, Dinner Plains and 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 Omeo’s water supply system which was used as a basis for the preparation of the initial WSDS in 2007.

EGW Water Supply Demand Strategy (2007)

This document forms EGW’s current WSDS for all of its water supply systems and forms the basis from which this updated WSDS has been developed upon. The 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. Omeo falls within the Mitta Mitta River SWMA which is listed as Category 3* (Water resources highly developed).

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:



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).

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.

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

Omeo is located within an Unincorporated Areas therefore no caps on groundwater use have been established.

Figure 4: Groundwater Management Units in East Gippsland (SKM, 2007)

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. Butchers Creek is not a priority stream and is therefore not subject to the requirements of a SMP.

Regional River Health Strategy

Stream value for Butchers Creek, which supplies Omeo, is covered by the North East Catchment Management Authority Regional River Health Strategy (NECMA RRHS). Within this document Butchers Creek is not specifically noted as being of high value (NECMA, 2005) although it is subject to a wider strategy devised for



waterway health within Omeo and the district. The wider strategy aims to protect and rehabilitate waterways in the upper Mitta-Mitta catchment that flow into Lake Dartmouth.

This is to be achieved by:

Implementing the Strategy that outlines the program objectives pertaining to waterway environment, channel stability, vegetation communities, water quality and the management actions.

Continuing works and planning of program for English Broom control works with Parks Victoria along the Mitta-Mitta River; fence and revegetation and willow removal works on the Livingstone Creek and Victoria River with landholders.

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.

Butchers Creek 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 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).

http://www.envict.org.au/inform.php?menu=7&submenu=220&item=668

Some of the Legislation that should be considered in the development of any water supply solution includes:

Water Act 1989

Flora and Fauna Guarantee Act 1988

Environment Protection Act 1970

Planning and Environment Act 1987

Environment Effects Act 1978

National Parks Act 1975

Fisheries Act 1995

Wildlife Act 1975

Catchment and Land Protection Act 1994

Environment Protection and Biodiversity Conservation Act 1999



4.0 Water Demand The following sections of this report estimate the current demand at Omeo and outline the likely future demand.

4.1 Current Demand

Historical water usage data for Omeo was obtained from the 2006 DRP (see Table 1). Current water usage data was obtained from bulk water meter data (Table 2) and customer billing records (Table 3).

The 2006 DRP presented detailed demand forecasts based on historical average annual diversion rates (68.1ML) based upon demand data from July 2003 to June 2005. To confirm these demands recent bulk meter data was extracted from EGW’s SCADA system and customer billing data was extracted from EGW’s billing system (2006 – 2009 based on financial years).

Table 1: Monthly Water Demand (based upon the DRP - SKM, 2006)

Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Total Annual Demand (ML)

3.5 3.8 4.3 5.4 6.2 7.6 8.7 7.9 7.4 5.4 4.3 3.5 68.1

% of Annual Demand

5.1 5.6 6.4 7.9 9.1 11.2 12.7 11.6 10.9 8.0 6.3 5.1 100

Table 2: Bulk Water Meter Data

Meter Readings (ML) 06-07 07-08 08-09 Butchers Creek Off-take 66.5 54.5 57.35 Town Water Meter 50.8 42.8 53.77

Table 3: Customer Billing Data

Water Use (ML) 2005-06 FY 2006-07 FY 2007-08 FY1 2008-09 FY Residential 32.05 30.39 23.89 30.54 Non Residential 18.50 17.09 13.36 15.94 Total 50.55 47.48 37.25 46.48 Population2 207 209 210 212 Residential Connections 168 175 174 178 Non Residential Connections

62 63 63 66

Per Capita Water Use3 (L/capita/day)

249 227 179 224

1 Heavy restrictions resulted in a significant reduction in water use

2 Based on Victoria in Future Data Projections for the East Gippsland Region (2008)

3 Calculated based on residential demand and the predicted population

Customer billing data for the last year was reviewed to identify those users with high demand (in excess of 1ML per annum). The customer’s demands are shown in Table 4.



Table 4: Users with high water demand

Customer Demand (ML/yr)

Customer 1 1.2

Customer 2 1.2

Customer 3 1.8

Customer 4 1.9

Customer 5 2.1

The previously established water demand of 68.1ML per annum (SKM, 2006), is relatively consistent with bulk meter data from 2006-07 and 2008-09, although a significant reduction in customer demand occurred during 2007-08. This reduction can be attributed to the stringent water restrictions that were put in place during this time.

Furthermore it is evident that significant losses occur between the Butchers Creek offtake and the town water meter (22%). EGW has since identified and rectified the source of some of these losses (as is reflected in the latest bulk water meter readings).

Based on the data provided above in Table 3, the non-residential component of the demand equates to 36% of total demand. The average annual cumulative demand for the top five water users in Omeo is approximately 8.2ML. The five top water users and their demand for the last year are summarised in Table 4.

4.1.1 Summary of Current Demand

Best practice water supply planning is to use long term average demands for determining existing per capita water demand. This appears to be a sound approach for Omeo as there is no certainty that the recent drop in per capita consumption will continue if wetter conditions return. It has been assumed that the population, and hence demand, at Omeo has remained relatively constant during the period between 2006 and 2009. It is therefore estimated that the current annual water demand (including non revenue water) for Omeo is in the order of 68ML per annum.

Monthly demands patterns outlined in 2006 DRP will be used in this study as they are most likely to represent unrestricted demand patterns.

4.2 Forecasted Water Demand

4.2.1 Previous Population Projections

In determining population projections for the previous 2007 WSDS, observed trends were compared to the 2006 Victoria in Future population projections. Although both of these data sources suggested a decline in the permanent population, it was highlighted that the magnitude of the predicted decline (67% over 50 years) appeared unreasonable. To put it in context these predictions would see Omeo’s permanent population reduce to only 68 by 2059.

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 presented in Table 5 in comparison to the 2001 Census data results.



Table 5: Census Data (2001 and 2006)

Year Persons Counted at Home

Total Dwellings

2001 223 1221 2006 207 90 1 It should be noted that several of these dwellings were not fixed structures (i.e. caravans and mobile homes)

It can be seen that the permanent population in Omeo declined between the 2001 and 2006 census periods, with an annual rate of decline of approximately 1.5%. The rate of population decline has therefore slowed from the 2.5% per year that was experienced between 1996 and 2001 (2007 WSDS).

4.2.3 Victoria in Future Data

The smallest regional breakdown of data available from Victoria in Future is for the East Gippsland Statistical Division (EGSD). Available projections for 2008 suggest an increase in population throughout the region however these projections include major urban centres such as Bairnsdale, Lakes Entrance and Orbost. The 2008 projections for the region excluding these major urban centres (statistical balance) is yet to be released, however preliminary discussions indicate that the predicted population decline may not be as significant as previous projections indicated. The previous Victoria in Future projections suggested a decrease of between -1.5% to -2.5% (2007 WSDS).

East Gippsland is a vast and diverse region, with beachside towns, inland farming and forestry communities as well as alpine communities. Omeo’s proximity to the Alpine ski fields makes it unique from many of the other small towns in East Gippsland and therefore population predictions from Victoria in Future should be treated with caution.

4.2.4 East Gippsland Shire Council

Discussions were held with East Gippsland Shire Council (EGSC) to confirm the appropriateness of the population estimates for Omeo. Council advised that while they do not complete there own projections they are not expecting any significant changes to growth in Omeo, if anything they expect a slight incremental increase.

4.2.5 Adopted Trends

There is much uncertainty regarding Omeo’s future population growth. Census data confirms that the population has been declining for some time which is consistent with previous projections for the EGSD from Victoria in Future. Despite this historical decline it is apparent that the rate of decrease is slowing and in fact Council now anticipate a slight increase in the town’s population. To plan for this uncertainty it was determined that two alternatives would be considered for future population growth. These alternatives are discussed in Section 4.3 of this report.

4.2.6 Commercial and Industrial Water Use

It has been assumed that commercial/industrial demand will increase at a rate consistent with residential growth.

The suitability of this assumption was confirmed by reviewing customer billing data between the 2005/06 and 2006/07 financial years. This data showed that residential demand reduced by 7% and commercial/industrial demand reduced by 8%. The difference between the reductions is considered to be minimal given that Omeo is a small town.



4.3 Summary of Demand Projections

Based upon the information presented above, two alternatives are to be modelled to account for the uncertainty of future changes in Omeo’s population:

Alternative 1 - No change in population (and hence demand), considered to provide a worst case scenario consistent with EGSC’s thoughts on growth.

Alternative 2 - Decline in population (and hence demand), consistent with the most recent census data (i.e. 1.5% per annum decline), providing a best case scenario.

The two demand alternatives are shown graphically in Figure 5.

Figure 5: Demand Alternatives (including non revenue water)

Demand in 2006 was around 68ML/annum and Alternative 1 would see this demand remain constant over the planning period. Alternative 2 shows a progressive decrease in demand associated with a decline in population.



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. 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:

The introduction of a mandatory water efficiency labelling for appliances (commencing 2006) under the national Water Efficiency Labelling and Standards Scheme (WELS);

The introduction of rising block tariffs, which result in higher charges for high water users; and

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.

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 Omeo.

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 Victoria in Future population projections. From this information the average daily water use is 220L/day per person (based on data available for the period between the 05/06 financial year and present). The average daily per capita demand is likely to be overestimated as it’s been determined based upon the permanent winter population (i.e. the census data was collected in August of 2006). Omeo can be subject to significant visitor numbers at this time of year which when taken into account will significantly reduce the per capita demand.

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:

A 25% reduction in per capita demand by the year 2015 relative to 1990s average demand; and

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:

East Gippsland Water will continue to work with its major customers to reduce the water use of those major customers.

East Gippsland Water will continue its leak reduction program.



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:

The State Government will extend its existing water savings behavioural change program until 2015. – This program is still running

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

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

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

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.

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

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

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.



6.0 Water Supply The long term average annual streamflow for Butchers Creek is 2864 ML. The last few years have been significantly drier with 2002 to 2004 being well below the long term average flow rate. A cease to flow event occurred in 2009 however this is not shown on the graph as the data was unavailable when the strategy was being revised.

Figure 6: Modelled and Historical Streamflows for Butchers Creek

The future volume of water available for extraction at Butchers Creek will be dependant on a number of factors such as:

Rainfall and runoff;

Groundwater baseflows;

Climate change;

Impact of bushfires; and

Forestry.

The following sections of this report discuss some of the issues around future water availability and identify a number of scenarios that will be used for modelling.

6.1 Impact of Climate Change

The greatest concern for Omeo’s water supply system relating to climate change is a significant reduction in the volume of water available for extraction.

A report titled “Rainfall-runoff modelling across the Murray-Darling Basin” by the CSIRO (2008) was used as the basis for obtaining stream flow reduction figures. A 37% reduction in stream flows is shown for the Murray region, which includes the Butchers Creek catchment (Omeo’s current water supply source).



The CSIRO report states that:

“Almost all the gauged catchments available for model calibration are in the higher runoff areas in the southern and eastern Murray-Darling Basin (MDB). Runoff estimates are therefore generally good in the higher runoff areas but comparatively poor elsewhere.”

The Butchers Creek catchment is located in the south eastern corner of the MDB and so the figures derived in the report are assumed to be applicable to that catchment.

The 37% reduction in stream flow by 2030 was the “dry” (or worst case) scenario in the report. The AECOM climate change group provided advice that this would be the most appropriate scenario to consider given that the background inputs to this modelling scenario most closely represent current climate measurements.

The median scenario outlined in the CSIRO report predicts a 10% reduction in streamflow by 2030 due to the impacts of climate change.

DSE’s Sustainable Water Strategies also consider the possibility that we have already experienced a step change in climate change and include a scenario that assumes a continuation of the last 10 years of low flows. This was not considered to be a critical scenario for Omeo due to the following:

The Gippsland Region Sustainable Water Strategy: Discussion Paper (2009) states that:

“While much of southern Victoria, including west Gippsland, has experienced the lowest 12 years of rainfall on record, conditions have been slightly less extreme in central and eastern Gippsland, with rainfalls falling into the below average and very much below average categories.”

and

“The reduction in average annual rainfall across the state over the last 12 years (around 12 per cent) is in fact around the same as during 1936 – 1945 but this earlier drought period was not characterised by the large reductions in autumn rainfall that we have seen in recent years”.

The statement that the period between 1936 and 1945 experienced even greater reductions in rainfall than the current drought is confirmed by Figure 6 above and also by the storage drawdown modelling in Section 7. This suggests that although the recent drought events have had a significant impact on Omeo’s water supplies, there is the risk that futures years could be much worse.

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 Butchers Creek catchment upstream of the town offtake is largely native forest. EGW estimates that approximately 38% of the catchment was burnt during the 2003 bushfires.

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 7 below. The curve details predicted changes in streamflow resulting from the 2003 bushfires for the Dartmouth Catchment within which Omeo resides. The curve provided by DSE was taken from a preliminary report investigating the impact of the 2003 and 2006 bushfires on streamflows (only 2003 fires impacted the Butchers Creek catchment); the report was yet to be published at the time this strategy was written.



Figure 7: Estimated reduction in streamflow due to bushfire (SKM, unreleased)

The curve 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.

Streamflow reductions for key modelling time steps are interpolated from Figure 7 as follows:

The current impact of the 2003 bushfires in terms of changes to streamflow is negligible (i.e. 0% change)

At 2030 it is expected that the reduction in streamflow associated with the bushfires will be around 11%

At 2060 the expected reduction in streamflow associated with the bushfires will be around 7%.

EGW has estimated that around 38% of the Butchers 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 have provided an appreciation for the complexity of the interactions between climate change and the impacts associated with bushfires. DSE have 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 test the sensitivity of the model results to the magnitude of bushfire impacts, streamflow reductions are reduced by 50% (to 5.5% in 2030) in one of the scenarios presented in Section 7.

6.3 Forestry

The Butchers Creek water supply catchment has historically been subjected to logging. Similar to the impacts of bushfires, logging reduces streamflows in the long term as the forests re-establish. It is understood that it is planned to log a further 2sq/km of the Butchers Creek catchment over the 2009-10 period, this is equivalent to 9% of the catchment. Continued logging is likely to impact upon the streamflow within Butchers Creek. To improve water supply reliability, it is recommended that EGW continue to seek a reduction in the area to be logged within Omeo’s water supply catchment.



6.4 Future Streamflow Projections

The effect of potential climate change and bushfire impacts on future streamflow is demonstrated in Figure 8. It is clear that climate change poses the greater risk to Omeo’s water supply reliability.

Figure 8: Future Streamflow Projections

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



7.0 Reliability of Supply The storage at Omeo operates as a ‘within year storage’ that is fed from an unregulated stream (Butchers Creek). Unlike “carry over” reservoirs on larger supply systems, “within year” reservoirs 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 Omeo’s reservoir occurs during summer and drawdown can occur quite rapidly when Butchers Creek approaches cease to flow conditions. This section describes how behavioural simulation analysis using a REALM model was used to assess the likely performance of different reservoir sizes under different future supply and demand conditions.

7.1 REALM Modelling Method

A brief summary of the modelling method, key assumptions and results are presented below.

7.1.1 Method Overview

The method adopted for the REALM modelling can be summarised as:

Review previous SKM model and identify any issues;

Collate streamflow data and update where possible;

Develop scenarios for analysis;

Set restriction triggers (refer to Section 7.3.2 for details); and

Undertake modelling and produce output graphs.

7.1.2 Modelling Assumptions

The key assumptions made during the modelling exercise are summarised as follows:

Streamflow Data

It is assumed that the flow past gauging station 401228 is the same as the flow past the off take point;

Gauged data collected by Thiess between 1991 and 1999 was used in preference to all other data when available;

The streamflow estimates from the HYDROLOG model which SKM created as part of the DRP was assumed to represent a good relationship between rainfall and runoff and was used for data between 1900 and 2005;

Between 2005 and 2006 average weekly flow values were used to extend the flow record; and

From 2006 to 2009 EGW provided readings from gauging station 401228. These reads were generally weekly and were averaged to create an additional 3 years of streamflow data. Missing values were filled in with averages.

Demand Data

The previous demand data model was not checked. It was assumed to be sufficient in the form it was provided;

For demand data beyond 2005 (where the previous demand model ended) average demand figures for each week of the year were used; and

For two of the scenarios a reduced demand figure was used. This was base on a 1.5% population decline per year until 2035 with a total demand reduction of 47% being applied to the demand dataset. This assumes that population and demand are linearly linked.



Climate Change

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;

The reduction in streamflow will occur in a linear fashion, reducing by a fixed amount each year between 1990 and 2030; and

The predicted reduction in streamflow is outlined in Chiew et al 2009. Further discussion is provided in section 7.3.1.

REALM Model

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

Loses due to evaporation from an uncovered reservoir have not accounted for by the model. Preliminary calculations indicate that losses due to evaporation would be minimal (<0.1ML/annum), therefore this approach is reasonable.

7.2 Current Reliability of Supply

The existing system (which includes 5 ML of offstream 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 68ML and a 17% reduction on historical streamflows resulting from the dry climate change scenario. Bushfire impacts are considered to be minor at this point in time as 2009 is at the transition point of the initial streamflow increase and future streamflow reductions. Figure 9 (next page) shows that with the changed climatic conditions, Stage 2 restrictions would be required on average once every 4 years. This is significantly more frequent that EGW’s LOS objective of restrictions being required no more frequent than once every 10 years.

The nature the existing supply system is that the storage can both empty very quickly and fill very quickly. Streamflows are consistently above the maximum offtake capacity for all but the driest months in the driest years. When the offtake operates at maximum capacity the storage will fill in approximately 2-3 weeks. Conversely, when the creek ceases to flow, the storage could empty in 2-3 weeks.



Figure 9: Reservoir drawdown under current operating conditions



7.3 Future Reliability of Supply

7.3.1 Future Supply and Demand Scenarios

To account for the uncertainty associated with climate change, bushfire impacts and population growth, three scenarios were created to determine what additional storage Omeo would require to meet EGW’s LOS objectives:

Scenario S1 – High Impact

The High Impact scenario is expected to present the worst case future water supply situation for Omeo and combines the most dire of predicted outcomes for each of the main variables (climate change, bushfire and population growth). Although it is likely that the impact of bushfires on streamflow will be lessened by a drier climate, this scenario uses the full reduction as worst case as the magnitude of this interaction can not be quantified.

This scenario is only modelled at 2030 as this is the critical time for both bushfire impacts and climate change. Population is considered to be stagnant in this scenario.

Scenario S2 – Moderate Impact

The Moderate Impact scenario is expected to present the best case future water supply situation for Omeo and combines the best predicted outcome for each of the main variables (climate change, bushfire and population growth). This includes medium climate change, the full impacts of the 2003 bushfires and a declining population (1.3% per year). As the climate change predications are less extreme, it is considered more likely that the full impact of bushfires will occur under this scenario.

Given that climate change has been tracking towards the ‘dry’ climate change scenario, the ‘wet’ scenario has not been considered as part of this investigation and medium climate change has been considered the “best case” future outcome for Omeo.

As this scenario includes a declining population, the scenario was modelled at 2009 when the demand is critical and at 2030 when bushfire impacts and climate change are critical.

Scenario S3 – Intermediate

The Intermediate Scenario uses the most likely occurrence of each of the three main variables. The dry climate change scenario (37%) 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 (to 5.5% in 2030) in the magnitude of the bushfire impacts was adopted given the 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 more discussion). Stagnant population has been assumed as it seems unlikely that the population in Omeo would continue to decline indefinitely (which is backed up by a recent slowing in the rate of population decline). This also takes in consideration Council’s informal advice that they expect a slight increase in population and from Victoria in Future that they expect little change in the population of small towns throughout East Gippsland.

This scenario is only modelled at 2030 as this is the critical time for both bushfire impacts and climate change. Population is considered to be stagnant in this scenario.

Table 6: Summary of REALM Modelling Scenarios

Scenario Reduction in Streamflow from Climate Change

Reduction in Streamflow from Bushfires

Population growth

S1 – High Impact 37% 11%1 Stagnant S2 – Moderate Impact 10% 5.5%1 1.5% decline S3 - Intermediate 37% 5.5%1 Stagnant 1 Reduction only applied across 38% of catchment that was burnt



7.3.2 Setting Restriction Triggers

Storage requirements are 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:

The desired frequency of restrictions (defined by EGW’s LOS objectives)

Allowing sufficient time between restriction levels for community adjustment

Allowing sufficient time for EGW to arrange emergency supply arrangements in the rare event of reservoir failure

The following method was adopted for setting trigger levels in the REALM model:

The Stage 1 restriction trigger was set equal to the 1 in 10 year drawdown event in accordance EGW’s Level of Service (LOS) objectives.

The Stage 2 trigger was set 3 ML below the Stage 1 trigger to allow the community time to adjust their behaviour from voluntary restrictions to mandatory restrictions. This would equate to 12 days of supply in a cease to flow event.

Stage 3 and 4 were combined to minimise storage requirements. Their trigger level was again set at 3 ML below the Stage 2 trigger level. This equates to 15 days of supply at a cease to flow event. Emergency Storage was also incorporated into the design criteria. 2ML of storage was allowed beyond the Stage 3 and 4 trigger level.

7.3.3 Summary of Future Reliability of Supply

The modelling results are summarised below in Table 7, and the behaviour analysis for the recommended planning scenario is shown in Figure 10. Detailed results are contained in Appendix A.

Table 7: Summary of REALM Modelling Scenarios

Drawdown to stage 1 restrictions

Total storage required1

Frequency of stage 3/4 restrictions

Reservoir depletion at onset of stage 1 restrictions

Frequency of reservoir failure

Scenario 1 (2030) 8ML 15ML 1 in 100 50% 1 in 100 Scenario 2 (2009) 4.5ML 12.5ML 1 in 100 35% 1 in 100 Scenario 2 (2030) 2ML 10ML – 6ML2 1 in 100 35% 1 in 100 Scenario 3 (2030 – stagnant population)

7.5ML 15ML 1 in 100 50% 1 in 100

Scenario 3 (2030 – declining population)

3ML 11ML - 7ML2 1 in 100 27% 1 in 100

1 (includes 5 ML existing storage)

2 Due to the reduced rate of drawdown it may be appropriate to reduce the buffer between restrictions from 3ML to 2ML or

even 1ML.

The results confirmed that population growth and climate change have a much larger impact on storage requirements than bushfire impacts. In determining the optimum size for a new storage dam it is recommended that EGW adopt planning Scenario 3 (stagnant population) and construct a new 10ML storage which would provide 15ML storage in total. This scenario is based on AECOM’s interpretation of the most likely climate change and bushfire scenarios. Within this scenario, two alternatives were considered for population change, it is recommended that EGW plan for the more conservative of these alternatives given the economies of scale associated with construction of open reservoirs. The additional storage would have the added benefit of being a fire fighting resource during future bushfires as was the case during the 2003 bushfires when the existing storage was used to supply fire bombers.



EGW are investigating the suitability of the abandoned raw water storage site as an option for providing this additional storage. Pumping costs are not expected to be significant as the storage will only be drawn from during critical periods.

Note: Subsequent to the modelling undertaken as part of this WSDS (detailed above) it was decided to combine the Stage 1 and Stage 2 restriction trigger, and raise the restriction trigger level for Stage 3 and 4. This provides EGW with a greater response time at Stage 3 and 4 restrictions and a reduced number of restrictions to be moved through during drought. The revised triggers have been verified and confirmed to meet EGW’s LOS objectives. The revised restriction triggers for adoption by EGW are listed as follows:

Stage 1 and 2 – 8ML of storage remaining (frequency 1 in 10 years)

Stage 3 and 4 – 3.5ML of storage remaining (frequency 1 in 100 years)



Figure 10: Modelling Results – Scenario 3



8.0 Alternative Supply Options The modelling undertaken in Section 7.1 of this report showed that 10 ML of additional storage would be required to secure Omeo’s water supply. In this Section, alternative water supply options are considered in comparison to the baseline solution of additional storage.

8.1 Surface Water

Three potential alternative surface water options were identified for Omeo, these include:

Livingstone Creek (Omeo’s historical water supply source prior to the establishment of a bulk entitlement on Butchers Creek);

Victoria River; and

Mitta Mitta River.

All three surface water bodies are located within the Mitta Mitta River SWMA which is listed as Category 3*. This means that that the management area is fully developed in terms of both allocation and diversion.

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. reclaimed water).

The Mitta Mitta River between Lake Dartmouth and Glen Valley is heritage listed and is therefore subject to the requirements of the Heritage Rivers Act (HRA). 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.

Gauging records for the three potential waterways was available for the following periods:

Livingstone Creek @ Omeo – Data available between 1968 – 1994

Mitta Mitta River @ Hinnomunjie – Data available between 1954 – 2008

Victoria River @ Victoria Falls – Data available between 1989 – 2008

Review of stream flow data shows that:

Livingstone Creek (~2.5km) is the closest stream to Omeo followed by Victoria River(~12km) and then the Mitta Mitta River (~13km)

Between 1968 and 1994 Livingstone Creek ran dry on approx 3 occasions (Jan 1983 for a few days)

Between 1954 and 2008 the Mitta Mitta River ran dry 5 times between 1954 and 1956 and had a streamflow under 100ML/day on approx 12 occasions

Between 1989 and 2008 the Victoria River ran dry on around 10 occasions and ran at less than 5ML/day for significant periods during 1998 and 2006.

The streamflow graphs from which these observations have been made are provided in Appendix B to this report.

Streamflow data also indicates that:

Livingstone Creek would be the most ideal stream in terms of reliability. However, given that records have only been kept until 1994, the reliability of the stream may be overestimated. Given that there is an irrigation ban currently imposed on Livingstone Creek it is unlikely to be a reliable source for Omeo.



Victoria River has a low reliability given that it has a probability of running dry once in every two years (based on the available 20 years of data).

Mitta Mitta river may be the most reliable water supply source for Omeo, although it is located furthest away and water trading will be required to gain access. Consideration will also need to be given to the extraction point as much of the river north or Omeo is heritage listed.

Livingstone Creek

Livingstone Creek was Omeo’s primary bulk supply source prior to EGW’s bulk entitlement being transferred to Butchers Creek. The reasons for this transfer were improved water quality and greater reliability (although no technical reports were available to confirm this). Given that delivery infrastructure already exists for this supply source, it could be perceived as a favorable emergency water supply source for Omeo. However, preliminary analysis shows that Butchers Creek and Livingstone Creek have a similar response to runoff which suggests that when Butchers Creek experiences a supply shortage, it is likely that Livingstone Creek will also be experiencing a shortage. This argument is strengthened by the previous decision to abandon Livingstone Creek as supply source partly for reliability reasons. If a new license were to be pursued on Livingstone Creek it is likely that extraction during low flows would be restricted.

It is possible that water trading could be undertaken to obtain an allocation for Livingstone Creek that would allow for extraction over dry summer periods, although this would need to be worked through with the NECMA.

Preliminary discussions held with the NECMA indicate that it’s unlikely that any new licenses would allow for the extraction of water during low flows (or critical periods when water is most in need). It is therefore favorable to continue with the Butchers Creek bulk entitlement which allows a percentage of flow to be taken at any time of the year.

Due to the issues associated with reliability, extraction and delivery of water from the Victoria River, this potential supply source has not been considered further in this report. Given the infrequent requirement for a back up supply to Butchers Creek it is desirable to avoid large scale infrastructure projects. While it would not be financially viable to construct a 13km pipeline to transport water from the Mitta Mitta River, there is potential to access this supply source via water carting (see discussion in Section 8.7).

Water Races (transfer from the Wentworth River)

A number of water races from the Gold Rush days are known to exist within the region. A water race is a man made channel used to divert surface water via gravity. The Jirnkee water race, listed on the Victorian Heritage database as the longest privately-owned water race in Victoria, has previously been identified as having potential to divert supply from the Wentworth River. The length of the Jirnkee water race has previously been estimated at 8km running through heavily vegetated areas.

In assessing the Jimkee water race or others as an emergency supply source, a number of issues require consideration:

Using an unlined open channel as a means of water conveyance would likely result in significant water losses and as such a pipeline would be required.

Construction of a pipeline would be both expensive (8km) and difficult given the access constraints

The race is now heavily overgrown and a significant number of trees would require removal to allow access for construction machinery

The environmental and social implications of transferring water away from the Wentworth River are likely to be significant

The water race is listed on the Victorian Heritage database which may inhibit any construction activities

For the above reasons the further investigation of the Jirnkee water race as an emergency supply source has not been considered further.



8.2 Groundwater

Omeo has a single drought relief bore (number 55931) which is reported by SKM (2007) to have a capacity of 1.2 l/s (0.10 ML/d). The bore is reported by SKM (2006) to have a Total Dissolved Solids (TDS) level of 940mg/L which is very close to the Australian Drinking Water Guidelines (ADWG) limit of 1000mg/L for acceptable taste. The location of the groundwater bore can be seen in Figure 2.

Based on review of data available for this bore (on the Victorian Water Resources Website) it would appear that the last time this bore was sampled was in 1969. At this time the Total Soluble Salts (or Conductivity) was measured as 940mg/L and the Electrical Conductivity (EC) was 1080µS/cm.

A second bore (number 86783) was identified in Omeo using the Groundwater Management System (GMS) database. This bore was last sampled in 1991 and had the following quality parameters:

Table 8: Groundwater quality parameters (bore 86783)

Parameter Measurement Electrical Conductivity (EC) 1100 µS/cm Total Suspended Solids (TSS) 781 mg/L pH 8.1

Based on these two bores it appears that groundwater in the immediate vicinity of Omeo is too saline for use as a bulk supply without some form of treatment. Building such a plant would not be cost effective given the scale and low frequency of use. As an emergency supply, it is possible to lease a privately owned mobile package plant, however preferential access to these assets in critical supply times could be difficult to secure. Should groundwater treatment be selected as an option requiring further investigation, consideration will need to be given to disposal of the brine.

A number of other groundwater bores have been identified outside of the Omeo township that appear to have a sufficient yield and quality, although they are generally located several kilometres away from the Omeo township. The bores identified with a suitable yield and quality (in terms of TDS) are outlined below.

Table 9: Potential groundwater bores outside of the Omeo Township

Bore Number

Electrical Conductivity

Yield (L/sec)

Depth (m) Approximate Distance from Omeo (m)

Lithology

49480 400 19 61 17,100 SAND 55931 1080 5.9 51.81 700 CLAY 67315 685 0.9 26.1 13,900 GRAN 67285 651 0.9 77.72 18,100 RHYL 67337 920 1.1 42.9 17,700 GRAN 67361 550 1.2 74 19,100 SHAL 67333 126 1.3 14.8 19,300 CLAY 86783 1100 0.9 43 12,500 SHAL

Utilisation of one of the bores with higher quality (in terms of EC) will require construction of a significant pipeline (around 18km in length) which is likely to render the cost of utilising groundwater prohibitive.

Although bulk supply of groundwater does not appear feasible, there is the opportunity to use groundwater as an emergency supply by blending into the raw storage. If the existing EGW bore (55931) were to be used this would require the construction of a pipeline approximately 2km in length for which the cost of construction would be prohibitive given the infrequent use. It would be more beneficial to construct a bore closer to the treatment plant or to cart the water from the bore to the raw water storage during an emergency situation.



It is estimated that construction of a new groundwater bore (closer to the raw storage) may cost in the order of $75,000. Prior to undertaking any design/construction a feasibility study would need to be conducted to determine the likely yield and quality and also to ensure the ongoing sustainability of extractions. Based on the estimated cost of the bore and the likely frequency of use it is estimated that the unit or marginal cost of water would be in the order of $6,000/ML exclusive of transportation costs.

From discussions with EGW it is understood that the football club also has a groundwater bore which could potentially be used during an emergency situation although EGW currently has no formal entitlement to extract water from this bore. If this option were to be considered further, it is recommended that EGW formalise access to this supply. Given that this bore is located around 1km away from the raw storage it would be more suitable to cart water from this bore during emergency situations as opposed to constructing a pipeline. The unit or marginal cost of carting water from this bore would be in the order of $4,000/ML.

Based on quality data collected from the raw water storage at the Omeo WTP it would appear that the water extracted from Butchers Creek has a TDS of around 43mg/L. The ADWG provide a guideline for drinking water supply of < 1000mg/L. Although the groundwater from the bores is high in TDS, it is still within acceptable limits according to guidelines. The ratio of groundwater to river water adopted in a blending situation would be a business decision to be made by EGW in terms of what quality of water they are willing to pass onto their customers.

The implications of providing raw water to the treatment plant with a significantly higher TDS than usual should be investigated further by EGW prior to adopting groundwater carting as an emergency water supply.

Based on the groundwater options identified above it would appear that the most appropriate groundwater solution would be to utilise both bore 55931 and the football oval bore in emergency situations. As these will only be used in emergency situations it is difficult to justify the capital expenditure of a pipeline 1-2km length. A more suitable alternative would be to cart water from these bores in times of need.

8.3 Water Loss Reduction

When comparing the water meter readings for the 2006-07 FY (in Table 3) and the bulk water meter readings for the same period (Table 1) it can be seen that approximately 20ML of water is lost between the creek off-take and customers meters. Some of this water is used by EGW for flushing the reticulation network, whilst some of this water is likely to be lost through the treatment process and system leakage. EGW recently identified the source of a significant proportion of the water losses within the system and this issue has now been rectified. The success of these works was been confirmed by the meter readings for 2008-09 FY.

A preliminary analysis has been undertaken to determine the impact of leakage reduction within the system on securing Omeo’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 Omeo providing only a few additional days of water supply during periods when the storage is progressively drawn down.

Given the recent success of leakage reduction activities it is considered that further reduction of non revenue water has only minimal potential for improving water supply reliability for Omeo. It is however recommended that EGW continue to monitor system losses to ensure the recent savings are maintained.

8.4 Recycled Water (from the Omeo WWTP)

The Omeo Wastewater Treatment Plant (WWTP) was constructed in 1996 along with the town’s sewerage system. The WWTP was designed to treat an annual sewage flow of 38ML which is equivalent to approx 450L per tenement per day. Treatment is undertaken by a lagoon based system with winter storage to hold treated effluent during months when irrigation water is not required. Treated effluent is provided to pasture lots for irrigation.

The EPA Discharge Licence for the treatment plant dictates a maximum discharge flow rate of 3ML per month. Average annual inflows to the wastewater treatment plant are estimated at 30.2ML per annum based on bulk water meter data. On average 22.4ML of recycled water per annum is provided for irrigation of a pasture lot. After irrigation of the pasture lot and assuming a loss of 10% through the treatment plant the remaining volume of recycled water available for use in Omeo is 5ML per annum.



Based on a review of the top five water users within Omeo, the only one that may be have a suitable use for the recycled water is Customer 3, a camp park with an annual demand of approximately 1.82ML/annum. To get enough critical mass to warrant a recycling scheme would therefore require plumbing retrofits of existing homes to allow outdoor irrigation and potentially toilet flushing. This comes at a considerable expense and does little to reduce unrestrictable demands.

8.5 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 1185L/house/day, rainwater could supply of 15% of the total household demand (or 178 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).

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 often prohibitive. 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 for such a small proportion of the demand (only 15%) is expected to limit the financial viability of this option. It has therefore been concluded that the installation of rainwater tanks to substitute potable demand is not a feasible option.

8.6 Stormwater

Water of a potable quality would be required to provide relief to Omeo’s water supply system as outdoor water use becomes restricted during periods of water shortage. The critical period for Omeo’s water supply system occurs during extended periods of no rainfall. Investment in a stormwater harvesting project is therefore unlikely to provide any significant supply during critical water supply periods.



8.7 Water Carting

Water carting should only be considered as an emergency supply in the event that Omeo’s water storages approach critically low levels. In this situation, water carting would be required infrequently (no more than 1 in 15 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 an emergency water carting agreement is currently in place with the NECMA for the supply of bulk water from the Mitta Mitta River. Discussions with the NECMA indicate that this supply could be formalised into EGW’s existing bulk entitlement for use in future emergency situations.

8.8 Options to Considered Further

The following water supply options will be considered further:

Option 1 - Expanding the existing bulk water storage (supplied by Butchers Creek)

Option 2 - Demand management and reduction of water losses

Option 3 - Water carting (as an emergency supply)

Option 4 - Groundwater blending (as an emergency supply)

Option 5 - Recycled water

Option 6 - Surface water supply from Livingstone Creek

The options for extracting water from the Mitta Mitta River, Wentworth River and Victoria River for bulk supply have not been considered further due to the length of pipeline required to connect these sources to the existing supply system.

In addition to this, the rainwater tank and stormwater harvesting options have not been considered further for the following reasons:

Rainwater has the ability to provide only 15% of the daily household demand (at a reliability of 90%) and would therefore have limited effectiveness in reducing non-restrictable demand (assuming that retrofitting is only undertaken outside the home).

The cost of retrofitting households to supply rainwater is expected to be high when compared to the volume provided

The infrastructure required for a stormwater harvesting scheme is considered to be cost prohibitive

Both options rely on rainfall which a number of studies have shown has significantly declined over the past 20 years.



9.0 Assessment of Supply Options

9.1 Multi Criteria Analysis (MCA)

To assess the options available for securing Omeo’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.

9.1.1 Selection of Criteria

The following criteria have been used to assess the impact of each option:

Table 10: MCA Criteria for Assessment

Criteria Measure

Economic

Net Present Cost $/ML

Environmental

Greenhouse Gas Emissions Average Kg CO2 equivalent per ML per Year

Impact upon environmental flow objectives Estimated relative impact

Impact on surface, ground and marine water quality Estimated relative impact

Impact on terrestrial ecosystems Estimated loss or gain of significant ecological vegetation classes

Recreation and Heritage Estimated impact on recreation and heritage

Social

Social Acceptability Estimated degree of opposition or acceptance by the local community

Reliability of Supply

Confidence of Success Level of confidence in option

Volume of water provided Potential increase in the volume of water available during critical supply periods

9.1.2 Weightings

Weightings have been applied to each of the criteria based on their relative importance to EGW. Economic and Reliability of Supply 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 11.



Table 11: MCA Weightings

Criteria Weighting (%)

Economic 35

Environmental 20

Social 10

Impact on Reliability of Supply 35

9.1.3 Results

The results of the MCA are presented below in Table 12.



Table 12: Summary of MCA Results

Option 1 ‐ New Storage

Option 2 ‐ Demand

ManagementOption 3 ‐

Water CartingOption 4 ‐

GroundwaterOption 5 ‐

Recycled WaterOption 6 ‐

Livingstone Creek

EconomicNet Present Cost 0 1 ‐2 ‐1 ‐4 0

Total Economic 0 1 ‐2 ‐1 ‐4 0Weighted Economic 0 0.35 ‐0.7 ‐0.35 ‐1.4 0

EnvironmentalGreenhouse Gas Emissions 1 3 ‐3 ‐1 ‐3 1

Impact upon environmental flow objectives ‐1 0 ‐1 ‐1 1 ‐1

Impact on surface, ground and marine water quality ‐1 0 0 ‐1 1 ‐1

Impact on terrestrial ecosystems ‐1 0 0 ‐1 0 ‐1

Recreation and Heritage 0 0 0 0 0 0

Total Environmental ‐2 3 ‐4 ‐4 ‐1 ‐2Weighted Environmental ‐0.4 0.6 ‐0.8 ‐0.8 ‐0.2 ‐0.4

SocialSocial Acceptability 1 ‐1 1 ‐2 1 1

Total Social 1 ‐1 1 ‐2 1 1Weighted Social 0.1 ‐0.1 0.1 ‐0.2 0.1 0.1

Other CriteriaConfidence of Success 2 2 3 2 2 1

Volume Supplied 3 1 1 1 1 1

Total Other 5 3 4 3 3 2Weighted Other 1.75 1.05 1.4 1.05 1.05 0.7

OVERALL SCORE 4 6 ‐1 ‐4 ‐1 1WEIGHTED OVERALL SCORE 1.45 1.9 0 ‐0.3 ‐0.45 0.4



9.1.4 Discussion

From the MCA it can be seen that the construction of a new storage provides the best overall outcome in terms of the economic, environmental, social and reliability of supply considerations. Demand management and leakage reduction also ranks highly although the application of this option will only provide a marginal increase to reliability of supply. As a result, demand/leakage management could not be used as a stand alone solution. EGW should continue to work with the community at Omeo to reduce water consumption and thereby increase the reliability of the water supply system.

Although supply from Livingstone Creek also ranks highly, its ability to provide supply during critical supply periods is unlikely.

Water carting and groundwater supply (also by carting) are attractive as emergency supply options as they require no capital investment. Although their unit or marginal cost of supply is high, the infrequency of supply make them far more attractive than other solutions that require capital investments for infrastructure than would be required no more frequently than once every fifteen years. Of these options groundwater would be a cheaper supply source however supply from the Mitta Mitta River provides a higher quality of water. The priority of these supply sources in emergency situations should be defined in EGW’s drought response plan.

Recycled Water Supply ranked poorly, and as a result has not been considered further.

9.2 Expected Scheme Costs

The proposed scheme to improve reliability of supply to Omeo is:

3) Improve reliability of supply by:

a. construction of 10ML additional usable raw water storage and

b. ongoing implementation of cost effective demand management measures

4) Provide emergency supply by:

a. Water carting from either the Mitta Mitta River or nearby groundwater bores

The estimated costs for the proposed scheme are outlined in Table 13. The costs are high level conceptual estimates only and are limited to an accuracy of +/-40%. Estimates should be confirmed during functional and then detailed design.

Table 13: Expected Scheme Costs

Scheme Component Conceptual Cost ($) Construction of a 10 ML bulk storage $600,000* Implement Demand Management and Leakage Reduction Strategies

Assess on case by case basis

Emergency carting from the Mitta Mitta River $5500/ML Emergency carting from nearby groundwater bores $4000/ML *Includes all design, planning and engineering fees



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.



11.0 Conclusions and Recommendations

11.1 Conclusion

With scientific evidence suggesting that climate change is tracking along the driest of scenarios, it is clear that EGW can not meet its current LOS objectives with the existing 5ML storage alone. A number of modelling scenarios were used to determine the volume of additional storage required to enable EGW to meet its LOS objectives. It is recommended that EGW adopt planning Scenario 3 and construct a new 10ML storage which would give the system 15ML storage in total. The construction of additional storage was compared to other alternative water supply options, however these were either limited in the amount of water they could supply to critical uses during critical periods or were simply too costly to consider.

Scenario 3 was based on AECOM’s interpretation of the most likely climate change and bushfire scenarios, while adding an element of conservatism by adopting the more dire of the population change scenarios. This conservatism in reservoir sizing is considered appropriate given the economies of scale associated with construction of open reservoirs. The additional storage would have the added benefit of being a fire fighting resource during future bushfires as was the case during the 2003 bushfires when the existing storage was used to fuel fire bombers.

It is also recommended that EGW continue to pursue water loss reduction and demand management within Omeo and that they should seek to formalise emergency water carting access to the Mitta Mitta river into the existing bulk entitlement for Omeo.

11.2 Summary of Recommendations

Following this update of the WSDS for Omeo, AECOM recommends that EGW:

Continue the current practice of extracting water from Butchers Creek as Omeo’s main source of bulk water supply;

Construct an additional 10ML of useable raw water storage to complement the existing bulk water storage;

Adopt the revised restriction triggers outlined in Section 7.3.2;

Investigate the feasibility of using the abandoned raw water storage as a site for the additional bulk storage;

Implement and monitor performance of demand management and leakage reduction strategies;

Formalise emergency access to the Mitta Mitta River for water carting into the existing bulk entitlement;

Seek to formalise emergency access to the groundwater bore at the nearby football oval;

Investigate the impacts of using high salinity feedwater at the WTP (in terms of the impact of operation and quality) and

Continue to seek a reduction in the area to be logged within Omeo’s water supply catchment;

Update Omeo’s Drought Response Plan.



12.0 References 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

DSE, Gippsland Region Sustainable Water Strategy – Discussion Paper

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.

SKM, (2007) Impact of the 2003 Alpine Bushfires on Streamflow - Seasonal streamflow response. Report for the Murray-Darling Basin Commission and the Department of Sustainability and Environment.

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

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


P:\60049414\8_Issued_docs\8.1_Reports\FINAL Omeo WSDS_150110_AECOM.docx Revision D - 15 March 2010 A

Appendix A

REALM Modelling Results

1.1.1 Scenario 1 – Higher Impact

Scenario 1 assumes worst case climate change, worst case bushfire impact and worst case demand (i.e. no growth). Modelling shows that:

To meet the LOS condition 1 (Stage 1 restrictions no more often than 1 in 10 years) the storage must be allowed to drawdown by 8ML or before the introduction of water restrictions.

15 ML of storage (in total) would be required to maintain the restriction regime described in Section 7.3.2.

Stage 3 restrictions would only be required once in every 100 years thereby easily meeting LOS condition 2 (Stage 3 restrictions no more often than 1 in 15 years).

The initial drawdown before the introduction of restrictions would be approximately 50% of the reservoir capacity.

On average, the 15 ML storage would fail only once every 100 years

Scenario 1 in 2030 Modelled with a 15.5 ML reservoir to satisfy the level of service requirement for stage one restrictions only being implemented 1 in 10 years. To account for the impact of climate change streamflow has been reduced by 37% in 2030 compared to 1990. To account for the 2003 bushfires streamflow has been reduced by 4.18% (11% reduction over 38% of the catchment). The demand has been left at the current 2009 demand level (average of 68 ML per year)

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Scenario 1 ‐ 2030 ‐ High Climate Change, High Bushfire Impact, Stagnant Demand

Reservoir Storage

Stage 1 Restrictions


Stage 3&4 Restrictions

1.1.2 Scenario 2 – Medium Impact

Scenario 2 assumes moderate climate change, worst case bushfire impact and reduced demand due to a declining population. As this scenario includes a declining population, the scenario was modelled at 2009 when the demand is critical and at 2030 when bushfire impacts and climate change are critical.

Scenario 2 (Year 2009)

At year 2009 when demand is critical, modelling results showed that:

To meet LOS condition 1 (Stage 1 restrictions no more often than 1 in 10 years) the storage draws down by 4.5ML before the introduction of water restrictions.

12.5 ML of storage (in total) would be required to maintain the restriction regime described in Section 7.3.2.



On average, the 15 ML storage would only fail only once every 100 years

Scenario 2 in 2009 Modelled with a 12.5 ML reservoir to satisfy the level of service requirement for stage one restrictions only being implemented 1 in 10 years. This scenario assumes moderate climate change. Climate change is expected to reduce streamflow by 10% by 2030 compared to 1990. By 2009 it is estimated that streamflow will have decreased by 4.75%. No reduction in streamflow for the 2003 bushfires has been applied as in 2009 there is no expected increase or decrease in flows. The demand has been left at the current 2009 demand level (average of 68 ML per year)

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Scenario 2 ‐ 2009 ‐Moderate Climate Change, High Bushfire Impact, Current Demand

Reservoir Storage




Scenario 2 (Year 2030)

At year 2030 when supply is critical, modelling results showed that:

To meet LOS condition 1 (Stage 1 restrictions no more often than 1 in 10 years) the storage drawdown by 2ML before the introduction of water restrictions.

10 ML storage in total would be required to maintain the restriction regime described in Section 7.3.2.




This Scenario suggests that the results are highly sensitive to population growth and therefore changes in water use.

The operating conditions for this scenario are probably a bit too excessive given the small drawdown experienced in most years. Given the observed storage behaviour it would be more appropriate to adopt 1-2 ML between restriction levels. This would require a total storage size of 6 - 8 ML.

It is clear that in the case of a declining population, the current situation is most critical and that reliability of supply can be expected to improve if Omeo’s population continues to decline.

Scenario 2 in 2030 Modelled with a 10 ML storage reservoir to satisfy the level of service requirement for stage one restrictions only being implemented 1 in 10 years. This scenario assumes moderate climate change. To account for the impact of climate change streamflow has been reduced by 10% in 2030 compared to 1990. To account for the 2003 bushfires streamflow has been reduced by 4.18% (11% reduction over 38% of the catchment). The demand has been reduced by 34% to simulate a 1.5% decrease in population per year (1.5% per year over 20 years).

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Scenario 2 ‐ 2030 ‐Moderate Climate Change, High Bushfire Impact, Reduced Demand

Reservoir Storage




1.1.3 Scenario 3 – Intermediate Impact

Scenario 3 assumes worst case climate change, moderate bushfire impact and stagnant demand. As Scenario 2 demonstrated the sensitivity of the results to future population projections, it was decided to also run Scenario 3 with a declining population.

Scenario 3 (Stagnant population)

Modelling of this scenario shows that:

To meet LOS condition 1 (Stage 1 restrictions no more often than 1 in 10 years) the storage draws down by 7.5ML before the introduction of water restrictions.

15ML of storage (in total) would be required to maintain the restriction regime described in Section 7.3.2.




The results of this scenario indicate that varying the magnitude of bushfire impacts has a limited effect on the volume of storage required for Omeo.

Scenario 3 in 2030 Modelled with a 15.5 ML storage reservoir to satisfy the level of service requirement for stage one restrictions only being implemented 1 in 10 years. To account for the impact of climate change streamflow has been reduced by 37% in 2030 compared to 1990. To account for the 2003 bushfires streamflow has been reduced by 2.09% (5.5% reduction over 38% of the catchment). The demand has been left at the current 2009 demand level (average of 68 ML per year)

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Scenario 3 ‐ 2030 ‐ High Climate Change, Moderate Bushfire Impact, Stagnant Demand

Reservoir Storage




Scenario 3 (Declining population)

The results of this modelling showed that:

To meet LOS condition 1 (Stage 1 restrictions no more often than 1 in 10 years) the storage drawdown by 3ML before the introduction of water restrictions.

11 ML storage in total would be required to maintain the restriction regime described in Section 7.3.2.




The existing 5ML storage would come extremely close to failure once every 15 years

Again it seems reasonable that the drawdown volume between trigger levels could be reduced in this instance. Adopting 1 – 2 ML between restriction levels would require a total storage size of 7 - 9 ML.

As demonstrated in Scenario 2, if Omeo’s population continues to decline then the current situation is critical with reliability of supply improving over time.

Scenario 1 in 2030 Modelled with an 11 ML storage reservoir to satisfy the level of service requirement for stage one restrictions only being implemented 1 in 10 years. To account for the impact of climate change streamflow has been reduced by 37% in 2030 compared to 1990. To account for the 2003 bushfires streamflow has been reduced by 2.09% (5.5% reduction over 38% of the catchment). The demand has been reduced by 34% to simulate a 1.5% decrease in population per year (1.5% per year over 20 years).

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Simulation Year

Scenario 3 ‐ 2030 ‐ High Climate Change, Moderate Bushfire Impact, Reduced Demand

Reservoir Storage





P:\60049414\8_Issued_docs\8.1_Reports\FINAL Omeo WSDS_150110_AECOM.docx Revision D - 15 March 2010 B

Appendix B

Streamflow Reliability Charts

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Documents

Omeo Water Supply Demand Strategy - East Gippsland Water · Omeo Water Supply Demand Strategy AECOM P:\60049414\8_Issued_docs\8.1_Reports\FINAL Omeo WSDS_150110_AECOM.docx Revision