Portfolio 3
Surface water (traditional sources)

 

This portfolio includes:

  • Water conservation
  • Recycled water (for non-drinking purposes)
  • Groundwater
  • Rainwater tank scheme
  • Dam enlargement:
    • Enlarge Mangrove Creek Dam by 80 gigalitres of storage
  • Water transfers
    • Transferring water from Mangrove Creek Weir to Mangrove Creek Dam

 

Environmental impacts

  • Impacts on terrestrial and aquatic biodiversity in and around dam and transfer pipeline
  • Medium energy use and associated greenhouse gas emissions
  • Reduced urban stormwater runoff due to utilisation of rainwater tanks
  • Additional studies required to confirm impacts on ground dependent ecosystems and aquifer health

 

Social impacts

  • Some temporary disruption for local residents during construction of dam and pipeline
  • Potential Indigenous and European cultural heritage impacts in the dam and pipeline areas based on preliminary investigations to date
  • Acquisition of easements may be required for pipe sections on privately owned property
  • Operation and maintenance cost of rainwater tanks transferred to customers

 

Reliability or system resilience

  • An enlarged dam increases the time to deplete our storages in droughts which improves the robustness of our supply system
  • Dams and transfer pipeline relies on rainfall and will not ensure ongoing supply of water in a long and severe drought
  • The lead time for dam raising is around 10 years including approvals and construction
  • Decentralised rainwater tanks have reliability risks for ongoing maintenance required by the owners
  • Additional studies required to confirm the long term sustainable yield of the groundwater systems

 

Cost

  • The estimated average incremental cost for this portfolio is $3.30 per kilolitre*. This is the total cost of the portfolio on a kilolitre basis across a 40 year period.
  • This includes both upfront costs to build and ongoing costs to operate the new assets across the 40 year period.
  • *Existing uncertainty exists for biodiversity offset costs associated with raising Mangrove Creek Dam. These costs are currently excluded from the $3.30 per kilolitre and will likely be significant.

 

Drought management plan

  • As the options within this portfolio are generally climate dependent (e.g. a dam relies on rainfall for it to fill up), this portfolio offers no added benefit to our drought management plan, which means in a prolonged and extreme drought we will still have a large drought management gap to fill (additional investments in a 20-30ML/day desalination plant would be required).

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Timeline

7
Draft plan being developed (community feedback is being considered along side technical work and analysis)
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