Borumba Pumped Hydro – the MRCCC’s Balancing Storage proposal

Borumba Pumped hydro

If approved, Qld Hydro’s proposed Borumba Pumped Hydro Energy Storage project will be the largest infrastructure project of its kind in Queensland, and a massive undertaking estimated to cost Queensland tax payers in excess of $14.2 billion dollars. For more information about the proposal, download the MRCCC’s overview document and/or download Qld Hydro’s factsheet.

The MRCCC has a number of concerns in relation to the proposal, which is yet to receive all the approvals needed from federal and state government for the exploratory works and subsequent construction to commence. Should the project be given the green light, the MRCCC has the following comments on the proposal.

• Environmental offsets must deliver tangible benefits for affected species and ecosystems as close as possible to where adverse impacts occur;
• Funding needs to be provided to improve the ecological condition of the lower Yabba Creek (remove cats claw and other invasive plants;
• Water quality within and downstream of the dam must be maintained by the owner/operator;
• Modelling of water availability to operate the Pumped Hydro Energy Storage (PHES) must consider the effects of climate change on future availability of water;
• The Borumba Dam PHES must deliver tangible benefits for environmental values in the Mary Basin and the Great Sandy Strait;
• Flows required to maintain the ecological health of the Mary River estuary and the Great Sandy Strait Ramsar listed wetlands are provided.

There are also some optimistic add-ons should the govt be looking beyond things it is legislatively required to do (eg offsets, comply with Mary Basin Water Plan etc) and be seen as a good environmental corporate citizen in the Mary Valley.

• Provide funding to preserve and enhance wild macadamias in the Mary Basin;
• Provide funding to remove redundant instream flow barriers within the Mary Basin;
• Provide recurring funding to Landcare and other groups in the Mary Basin to undertake riparian and other ecological restoration;
• Include dedicated environmental water reserves in Borumba and Baroon Pocket Dams to augment environmental flows in Obi Obi Creek, Yabba Creek and the lower Mary River.

Borumba Creek balancing storage proposal

A proposal to improve the proposed Borumba pumped hydro scheme – September 2024

If Qld Hydro receives all the approvals required for the project to commence, it will involve building a large new on-stream lower reservoir on the Mary River system at Yabba Creek.  This would result in approximately 50km of stream length above the proposed lower reservoir dam site and about 236 km of river downstream being directly connected to the operation of the pumped hydro system. The proposed new 224 GL lower reservoir is far in excess of the existing 46 GL Lake Borumba, which was built to regulate irrigation and water supply along the Mary River for towns, cities and industries downstream including Imbil, Gympie, Noosa and Tiaro. Allocations from the existing Lake Borumba also now provide water to the SEQ water grid via the Northern Pipeline Interconnector which extracts water from the Mary River downstream of Lake Borumba via the Goomong Pocket pump station.

Apart from the major direct environmental impacts of construction and operation of the proposed new 70 GL upper reservoir and underground power infrastructure (which this proposal will not reduce), many of the long-term ongoing adverse impacts of the Borumba PHES proposal stem from the lower reservoir being a large on-river component of the power generation system. These impacts are mainly related to the inherent requirement of the power plant to pump large volumes of water back and forth between the off-stream upper reservoir and the on- stream lower reservoir on a daily cycle. This will induce large fluctuations in water level, large areas of exposed soil being exposed to erosion and large daily patterns of water movement, all likely to keep fine sediments in  suspension throughout the lower reservoir. This has major downstream water quality and environmental implications both during construction and for the entire operational life of the project.

The Mary River system is home to many unique and protected species listed as Matters of National Environmental Significance (MNES). The river system has been identified as a priority system for reducing fine sediment loads to the Ramsar wetland and world heritage waters at its mouth and the southern Great Barrier Reef. The proposal to construct a very large on-stream lower reservoir also involves flooding significant areas of high quality lowland forest, listed as a critically endangered MNES, and destroying breeding habitat for other listed MNES species including teh critically endangered Mary River turtle and White-faced snapping turtle, the endangered Mary River cod and the vulnerable Australian lungfish. There is a significant legal precedent in that the impact on these species was the main reason that the much smaller Traveston Crossing Dam proposal on the same river system was refused federal approval under the EPBC Act in 2009.

Even with the proposed greatly enlarged lower storage, (an attempt to mitigate the impact of the pump cycle on water levels in the lower reservoir), it is likely that the operation of such an on-stream system will always be an unsatisfactory compromise between the requirements of the energy grid, the downstream water supply obligations of the lower reservoir and the nationally and internationally significant biodiversity values of the Mary River system. An unhappy lose-lose-lose compromise in the energy, water and environment nexus.

The MRCCC has contacted Queensland government ministers requesting that the state consider building a separate, closed loop balancing storage to serve as the operational lower reservoir for the PHES. We believe there is a suitable site in Borumba Creek for a 72 GL (approx.) lower storage, that could largely be hydrologically and environmentally isolated from the Mary River system.  Such a proposal would not involve significantly increased water transfer tunneling, and would not involve any significant alterations to the current proposal for the upper reservoir and power generation plant infrastructure. The proposal would involve building a new dam wall across Borumba Creek, impounding water at a Full Supply Level of somewhere between 170m and 200m AHD. This impoundment would provide no effective aquatic habitat and  no recreational use (similar to the proposed upper reservoir). It could then be designed and operated solely for the efficient industrial use of the power plant alone and would largely isolate the major negative impacts of that operation from the river system.

Because the Borumba Creek storage would provide the operational storage required by the powerplant, the replacement of the existing Borumba Dam could be at a significantly lower height than what is currently proposed, thus resulting in a greatly reduced environmental footprint for the whole system. Lake Borumba would be isolated from the regular operations of the powerplant and thus avoid many of the adverse impacts to water quality, recreational use, and downstream water supply.

Some estimated parameters for this proposal are listed in Table one.

The proposed new Borumba Creek storage would inundate existing National Park and State Forest land. However, this impact would be offset by the reduced inundation of National Park and State Forest required by a smaller raising of the water level in Lake Borumba on Yabba Creek (10m rise instead of 20m). Crucially, the land inundated in the proposed Borumba Creek storage has a much lower biodiversity value than the forest that would be lost under the current proposal. The total storage volume of the combined system would be slightly reduced, but still sufficient to completely de-water the entire pumped hydro system at its full capacity, if ever required.

Such a proposal is likely to significantly reduce the ongoing methane and greenhouse gas emissions generated by the project by isolating the pumped hydro system from the carbon cycle of Lake Borumba. The total hydraulic head of the PHES would be reduced, but this disadvantage may plausibly be offset by providing the ability to operate deeper daily charge and discharge cycles of the pumped storage system. The catchment of Borumba Creek is likely to provide sufficient yield to replace the majority of the evaporative losses of the PHES system (seepage losses from the system are unknown) although an initial fill of the PHES system would probably need to be largely sourced from Lake Borumba. The proposal would also allow the commercial operation of the Mary Valley Water Supply Scheme to be more easily separated from the operation of the pumped hydro system.

The MRCCC is currently seeking opportunities to discuss the Borumba Creek balancing storage proposal in more detail, and has requested a thorough independent technical and economic analysis while the Borumba PHES proposal is still at the preliminary stages of its assessment and design process. We believe this proposal could significantly reduce the ongoing environmental impacts of the Borumba PHES, significantly increase the ability to mitigate the residual impacts, and significantly reduce the requirement to find off-site offsets for the project. The proposal may offer some useful engineering efficiencies for the construction and operation of the pumped hydro plant and the upgrade of Borumba Dam. In addition, this proposal addresses a number of items within the recently released Terms of Reference.

Table 1. Borumba Creek balancing storage proposal.

Indicative calculations (approximate)

Notes

1. Calculations sourced from the IHA GRES tool, using Google Earth Engine calculation https://www.grestool.org/.
2. Calculations sourced from Department of Natural Resources, Survey Group, Engineering Services Drawing A3-202668, “Yabba Creek – Basin 138 – Borumba Dam – AMTD 1 km – Storage Data