Eurobodalla Integrated Water Cycle Management Strategy

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86 Eurobodalla Integrated Water Cycle Management Strategy Opportunity 1: Raise Deep Creek Dam In this opportunity drought storage is increased by raising Deep Creek Dam. The opportunity limits the environmental footprint of off-river storage mainly to previously disturbed areas and maximises use of the existing assets. The disadvantages of this option are that the whole scheme’s drought security is confined to one storage and there is a limit on Deep Creek Dam’s capacity for expansion. Thus in the unlikely event of any major water quality and/or structural problem with the dam, the ability of the headworks to meet demands would be reduced. This opportunity would further stress the already stressed Moruya River by increasing extraction. Opportunity 2: New Southern Off-River Storage This opportunity involves a Southern off-river storage to be filled by high flow band water from the Tuross River. This option spreads drought security over two storages, resulting in a reduced risk from water quality and/or structural problems. This opportunity also improves operational flexibility of the scheme whereby water could be selectively pumped from three river sources and moved in both directions to the demand centres. It also reduces the impact that a trunk main break between Moruya and Narooma would have on supply to the south of the shire. Further this opportunity helps to minimise urban extraction stress of the Moruya River by sharing extraction with the Tuross River. In the long term this opportunity would assist in meeting peak day demand in both Southern and Central areas of the shire without major distribution pipeline upgrades. It will also enable Council to meet at minimal cost any future conservative river flow access regime. Analysis indicates that it is possible to locate the storage high in a catchment to reduce the environmental impacts of a storage on the downstream catchment. Further, it is also possible to select a site that can be raised in the future to increase storage capacity. Opportunity 3: New Central Off-River Storage This opportunity is based on a central off-river storage to be filled from the high flow bands of the Moruya River. Extraction of water from the Tuross River would cease, protecting this river from urban extraction. However, this opportunity would result in increasing urban expansion stress on Moruya River and risk to regional water supply through greater reliance on a single source. Unlike opportunity 1 the drought security risk is spread over two storages resulting in reduced supply security risks from water quality and dam structural problems. Although, in this opportunity, the regional scheme could be supplied from a single water filtration plant, in the long term the coastal distribution pipelines may require significant upgrading to meet peak day demands. Unlike opportunity 2, in this opportunity any breakage in the trunk main to Narooma could result in prolonged supply interruptions. Any future conservative river extraction regimes would result in significant headworks costs. Analysis indicates that it is possible to locate the storage high in a catchment to reduce the environmental impact of storage on the catchment. It is also possible to select a site that can be raised in the future to increase storage capacity. However suitable locations for such a storage will incur high pumping costs. Opportunity 4: Desalination as New Supply Source This opportunity is based on either a 5 ML/d reverse osmosis unit driven by energy from the grid or a 5 ML/d composite MED-RO system driven by about 35 solar dishes. Additional information on desalination processes, unit costs and factors influencing site selection are provided in appendix M. There are two ways in which desalination could be used in
Eurobodalla Integrated Water Cycle Management Strategy Eurobodalla. The two options are either as a long term regular water source or as a drought contingency option. A desalination plant provides a drought proof supply source and the novel technology has potential to attract tourist visitation. It reduces the dependence on surface waters, however it produces a brine stream that must be disposed of. The plant needs to be located on the coast, which may reduce the visual amenity of the area and may be located on a potential development area. Desalination plants can be expensive to operate due to their high energy use, which can result in greenhouse gas emission. Like opportunities 2 and 3, it spreads risks associated with water supply including reducing reliance on extended delivery mains. Social and Environmental Aspects of the Long term Supply Opportunities The above opportunities, whilst being developed based on a 50-year planning horizon, will be implemented in stages. The TBL assessment table below provides the comparative environmental, social and economic benefit of each strategy option. Table 8-9 Social and Environmental Aspects – Long term Supply Opportunities Opportunities Social Environmental Opportunity 1 Raise Deep Creek Dam Opportunity 2 New Southern Off-River Storage Opportunity 3 New Central Off-River Storage Opportunity 4 Desalination Maximises use of existing assets Drought security confined to one storage Limited construction work Spreads drought security (and water quality) risk between two storages and two supply sources Acceptance (and social impact) of proposal to build new storage Reduced reliance on extended delivery mains Spreads drought security risk between two storages but extraction based on one supply source More water available to environment and irrigators on Tuross River Acceptance (and social impact) of proposal to build new storage High pumping costs Plant located on possible development area Technology has potential to attract tourist visitation Public acceptance of this option for potable uses (unknown) Enhances drought-proofing of the scheme Reduced reliance on extended delivery mains Expensive to operate Proposal footprint predominantly confined to previously disturbed areas Further increases extraction from Moruya River, although in high flows River harvesting shared between two sources Creates a new footprint and associated environmental impact Increased reliance on Moruya River and higher environmental impacts to river environment Tuross River environment protected High energy use, resulting in greenhouse gas emission Potential issues with brine disposal Reduced dependence on surface waters The Project Team ranked the above opportunities. The triple bottom line assessment represented in Table 8-10 provides the relative ranking of each strategy option. 87
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xviii TABLES Eurobodalla Integrated
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FACT SHEET 3 Rainwater Tanks 18 Eur
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FACT SHEET 9 Loss Reduction 24 Euro
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Page 64 and 65: 38 Number of Persons 2,500 2,000 1,
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Page 72 and 73: 46 Annual Volume (ML/Yr) 2,500 2,00
Page 74 and 75: 48 Demand ML/a Eurobodalla Integrat
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9.5 Mogo 9.5.1 Background 140 Eurob
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9.14.2 What are the Issues? 202 Eur
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9.15.2 What Are the Issues? 208 Eur
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214 ML/a 8000 7000 6000 5000 4000 3
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228 SCENARIO 1 Regional Water Suppl
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