This portfolio includes:
- Water conservation
- Recycled water (for non-drinking purposes)
- 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
- 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
- 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
- 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).