Warren-Blackwood Regional Water Supply Scheme
Project goal:
To support long-term water security for communities connected to the Warren-Blackwood scheme.
Status:
Planning and Construction
Delivery Date
Ongoing
What's happening?
The Warren-Blackwood Regional Water Supply Scheme (the scheme) supplies the towns of Manjimup, Bridgetown, Nannup, Greenbushes, Boyup Brook, Balingup, Mullalyup, Kirup, and Hester.
Historically, the scheme relied solely on independent local dams for its water supply. However, over the past two decades, declining rainfall and increased evaporation have significantly reduced surface water availability.
As climate change continues to impact the yield of surface water due to increasing evaporation and decreased rainfall, we need to plan to ensure local communities can continue to have access to secure drinking water supplies for generations to come.
To support our planning, we recently completed a comprehensive review of water source options to support the scheme. Based on this review, we have identified Yarragadee aquifer groundwater as our preferred option for the scheme’s water supply, supported by infrastructure upgrades and operational improvements.
Warren-Blackwood Regional Water Supply Scheme
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What are the next steps?
Infrastructure upgrades
- A new groundwater treatment plant in Nannup
- A new standby bore 300m from the existing bore at the Thomas Road site in Nannup
- New tanks and pipework at various Water Corporation sites
Groundwater Licence Application
We’ve applied to the Department of Water and Environmental Regulation (DWER) to increase our groundwater allocation. DWER is currently assessing the application, and a public notice will be published in state and local newspapers in June 2025 with details on how to provide feedback. You can find more information regarding the Groundwater Licence Application in the FAQ’s tab or via this fact sheet.
Community Information Sessions
We’d like to hear from you. Join our project team at one of our upcoming drop-in sessions to learn more and share your feedback:
- Friday, 6 June – Nannup Town Hall, Warren Rd, Nannup – 2 pm to 5 pm
- Saturday, 7 June – Nannup Farmers Market, 6 Adam St, Nannup – 9 am to 11 am
We will continue to review our options for further securing the scheme’s water supply into the future.
What work will be happening?
Standby Bore – Thomas Road, Nannup
To maintain a reliable water supply, we plan to construct a standby bore 300m from the existing bore at the Thomas Road site in Nannup.
- The new bore will alternate operation with the existing bore, allowing for maintenance without disrupting supply and providing a backup in case of bore failure.
- Construction of the new bore is currently expected to commence from late 2025.
Groundwater Treatment Plant - Nannup
This plant will treat groundwater, improving water quality. Currently, groundwater from the Nannup bore is pumped into Millstream and Manjimup Dams to allow natural settling of iron and manganese. However, this process results in groundwater mixing with lower quality surface water, and also results in water loss through evaporation.
- The new groundwater treatment plant will remove iron and manganese directly from the groundwater, allowing it to be supplied directly to customers.
- This will reduce water loss, improve water quality, and remove the need for dam storage.
- A new dosing plant will also be constructed on Appadene Road in Manjimup, replacing the current facility at Manjimup Dam.
Construction was initially anticipated to begin in late 2024. However, due to ongoing planning and design considerations, it is now expected to commence in 2027. Updates will be provided as the project progresses.
Transfer System - Various Sites
We are planning upgrades to increase the water transfer rate within the scheme. This includes:
- New tanks and pipework at the Thomas Road bore site, Lindsay Road, Brockman Road, and the Manjimup Dam bypass site.
- This work is expected to begin in late 2025 and will occur within existing Water Corporation sites.
Bypassing Millstream and Manjimup Dams - In the coming years we will bypass these dams, allowing treated water from the Yarragadee aquifer to be supplied directly to customers.
Millstream and Manjimup Dams will remain as contingency sources in the short to medium term, providing additional security as we implement these upgrades.
Why is this happening?
The South West’s water supply has traditionally relied on dams. However, declining rainfall and reduced inflows over the past two decades have significantly affected surface water availability.To address this, the scheme now integrates groundwater to supplement the dams.
As climate change continues to impact the volume and quality of surface water, we need to further reduce our reliance on surface water. Additionally, with the scheme nearing capacity, more water will soon be required to meet growing demand. Additionally, with the scheme nearing capacity, more water will soon be required to meet growing demand.
What work has been completed?
- Yarragadee aquifer pumping test - In late 2023 we completed an 8-day pumping test on the Yarragadee aquifer from the existing bore in Nannup. The purpose of this activity was to help assess the hydrogeological impacts that increased groundwater abstraction may have on the Yarragadee aquifer and the surrounding environment. The results of this test indicated that the Yarragadee aquifer can support increased groundwater abstraction to support the scheme without negatively impacting groundwater-dependent ecosystems, including the Blackwood River. These findings have been submitted to the Department of Water and Environmental Regulation (DWER) for assessment and validation.
- Millstream Dam Bypass - A new tank and dosing unit was installed in 2023 to improve water quality and allow the bypass of Millstream Dam.
- Greenbushes to Kirup Link - A new 16 km pipeline completed in 2022 to secure supply to Balingup, Kirup, and Mullalyup.
- Millstream to Greenbushes pipeline - A new 16.2 km pipeline, two new pump stations and two one million litre storage tanks were completed in 2017.
- Hester Dam remedial works - An upgrade to Hester Dam was completed in April 2011, ensuring the reservoir can continue to operate at full capacity. This project involved modifications to the dam embankment and new outlet works.
- Hester to Boyup Brook pipeline upgrade - Duplication of the existing 9km pipeline between the Hallett tanks and Boyup Brook was completed in 2015.
- Manjimup supply from Nannup bore - A new pipeline was completed in 2013 to link the Nannup bore to Manjimup Dam, improving drought resilience.
- Yarragadee Bore - Nannup - Constructed in 2009, now supplying around 75% of the scheme’s water.
Water conservation
To support achievement of this objective, water efficiency and other compliance measures will continue to be complemented by educational initiatives and partnerships as required. Information on the current Waterwise Towns program can be found here
Communities in the Warren–Blackwood are commended for embracing water conservation efforts to date.
The South West’s water supply has traditionally relied on dams. However, declining rainfall and reduced inflows over the past two decades have significantly affected surface water availability.
To maintain a reliable water supply, the scheme now primarily relies on groundwater from the region’s deepest aquifer, the Yarragadee aquifer, via a bore near Nannup. Since 2018, between 5% and 27% of the scheme’s water has come from local dams, depending on rainfall and inflow.
The Department of Water and Environmental Regulation (DWER) is responsible for water resource management across the State. They determine how much water can be taken from groundwater and surface water resources, while safeguarding the sustainability of the resource and protecting the water dependent environment. We are currently licensed in alignment with DWER’s South West groundwater areas allocation plan to take water from the Yarragadee aquifer from the Nannup bore.
DWER has initiated steps towards a review of groundwater resources across the South West Groundwater Areas, including the Yarragadee aquifer, over the coming years. This review will assess groundwater level trends to better understand potential risks across the region. The findings will help inform the assessment of our current licence application, support the assessment of future applications, and support future planning for public water supply.
The Yarragadee aquifer is the South West’s oldest and deepest aquifer that is used for water supply. It provides a robust supply, even in dry years because of its vast storage and limited connection to the surface environment and overlying aquifers in the area where we draw from.
If you would like to know more about groundwater management and aquifers visit www.watercorporation.com.au/groundwater.
The shortlisted water source options were:
- More water from the existing Yarragadee aquifer bore near Nannup. This is the preferred option.
- A small filtration water treatment plant for Manjimup Dam and/or Millstream Dam to treat water stored there for as long as the sources are viable. Due to changing conditions, we are not able to continue using these dams without treatment, as there are incompatible land uses within their catchments. This option was not preferred as it retains scheme dependence on inflow.
- A small borefield (two to three bores) drawing shallow groundwater near Manjimup. Investigative drilling was completed in early 2021. This option may yield up to 0.15 GL/year. This option was not preferred as it is not supported by DWER.
- A new Yarragadee bore at an alternative location where environmental impacts can be demonstrated to be acceptable if an increase in capacity is not able to be achieved from the existing Yarragadee bore. Although a site has not yet been determined for this option, it would likely be at least 20 km from the existing bore. This option was not preferred due to cost, and the environmental impacts (such as clearing) associated with a more distant bore.
To determine the preferred water source, we consider factors including:
- Water quality
- Drying climate patterns and rainfall/streamflow data
- Impacts on local ecosystems and flora and fauna habitats
- Aboriginal Heritage and Native Title rights
- Community feedback and impact on private landowners
- Water treatment requirements and amount of water needed
- Cost of supplying water to our customers, including building the required infrastructure
We recently completed a comprehensive review of water source options for the Warren Blackwood Regional Water Supply Scheme. This review assessed a range of options to maintain a reliable water supply, considering factors such as environmental sustainability, climate resilience, reliability, safety, and cost.
Based on these assessments and a comprehensive hydrogeological study, we identified groundwater as the most viable option for the scheme’s future supply. The study included monitoring and an aquifer pumping test which took place in December 2023, indicating that the Yarragadee aquifer can support increased groundwater abstraction to support the scheme without negatively impacting groundwater-dependent ecosystems, including the Blackwood River. These findings have been submitted to the Department of Water and Environmental Regulation (DWER) for assessment and validation.
Water Corporation is currently licensed by the Department of Water and Environmental Regulation (DWER) to abstract groundwater from the Nannup bore, with an allocation of 1.5 GL/year. We have applied to DWER to increase this to 1.9 GL/year, accessing additional water from the Public Water Reserve in the Yarragadee aquifer (water set aside as a future public drinking water source). We are seeking approval for the increased allocation and future abstraction based on a scheme storage trigger (see FAQs), and our application is currently being assessed by DWER. This will help meet demand over the next few years, though an additional water source will still be needed in the coming years.
While DWER is conducting a review of the Yarragadee resource, we propose to limit our abstraction from the Yarragadee aquifer bore when we’re able to.
To help manage our water supply effectively, we’ve proposed a storage trigger for 1 August each year. This means that on 1 August, we’ll assess the amount of water stored in the scheme’s dams.
- If storage levels are above the trigger value, we’ll limit groundwater abstraction to our current allocation of 1.5 GL.
- If storage levels are below the trigger value, we may need to increase abstraction to up to 1.9 GL to maintain a secure water supply for our customers.
This timing was chosen as it allows us to assess storage levels before the water year begins on 1 October, giving us a clear picture of what’s needed to support the scheme through the warmer months. This is illustrated in Figure 1.
Figure 1. Warren Blackwood Regional Water Supply Scheme storage trigger to 2028
This trigger will be in place until 2028, when we bypass the dams. This will help meet demand over the next few years, though an additional water source will still be needed in the coming years. If further groundwater is required beyond the current application, an additional application and further investigations may be necessary.
Verity Staniforth-Smith – Community Engagement Senior Advisor