Reduce water take from the Minjerribah aquifer

Stradbroke Island Management Organisation (SIMO) and other groups and residents are concerned that the aquifer on North Stradbroke Island (Minjerribah) does not have the capacity to keep supplying 60% of Redlands’ water needs without environmental harm to the Island.

Minjerribah aquifer level is falling

The Minjerribah aquifer relies solely on rainfall. For years, Minjerribah has not been receiving enough rain to replenish the aquifer so water levels are steadily declining.

Many Island wetlands, mangroves and koala habitats rely on water flows from the aquifer to survive. Drying swamps are prone to increased fire risk. Falling water levels in the aquifer can risk saltwater intrusion. The Island’s economy needs a healthy environment.

Water extraction/water mining from Minjerribah to the Redlands commenced in 1996. Since then, about 20 million litres (20 ML) a day (7.3 billion litres a year) have been pumped across the Bay – without a study ever being done to determine what are environmentally safe amounts to remove. 

During the millennium drought in 2007 – and following island protests – the first Minjerribah water study was begun.

But the subsequent government abandoned the study before critical triggers could be established to determine when the aquifer was reaching dangerously low levels, and before a management plan was completed. 

Now falling aquifer levels on Minjerribah are causing concern once again.

Since the last drought, the aquifer level in the vicinity of the extraction borefield hasn’t even recovered, let alone built up.

The aquifer could have been allowed to recover during the years of abundant rainfall across South-East Queensland. But that didn’t happen. 

Modelling of the Minjerribah aquifer delayed

Recently, authorities promised to release updated modelling of the aquifer which would indicate safe extraction limits. But this modelling is yet to appear. 

Modelling is only as good as the data fed in. SIMO has concern about both the data quality and built-in assumptions driving the model.  The yield from aquifers – how much can be safely extracted without environmental harm – is very difficult to determine, given the number of variables.

But if we don’t know:

• what harm water extraction has already caused Minjerribah’s environment
• the risk of current damage
• the extent of damage in future, given the same draw-down of water

then extraction should be suspended until the science is in. This is the rational course of action to ensure the resilience of the Minjerribah aquifer. 

Redlands can take more water from the grid

The Government and Seqwater could take some pressure off the aquifer by supplying more water to Redlands from the grid via the Eastern Pipeline Interconnector (EPI), and also by placing Redlands on water restrictions. 

This would be wise. These measures would allow the aquifer to recover. Why hasn’t this happened? 

In September 2019, Redlands was receiving 10-15 ML/day from the EPI (yet it has the capacity to deliver 22 ML/day), plus 5 ML/day from Leslie Harrison Dam – and the bulk, 20-25 ML/day, from Minjerribah. 

Increasing the amount of water supplied by the EPI would help. But the EPI is not able to supply all Redlands’ water needs: 40 ML/day.

If for any reason water from Minjerribah is not available, how would Redlands’ current water needs be met – let alone with added water demands of proposed developments like Toondah?

Community action to save the Minjerribah aquifer

Redlanders should be asking now about their future water security. 

Meanwhile, residents in the Redlands can each play a part in conserving water, as they did in the previous drought. 

Also, if you are a resident concerned about future-proofing the city’s water supply, there are some actions you can take to help save Minjerribah’s aquifer:

Send an email to the three authorities and ask: 

• Why isn’t more water being brought into Redlands from the grid, to take pressure off Minjerribah’s aquifer?
• What is an environmentally safe amount of water to export from Minjerribah, and what is the science to support it?
• What is the trigger level for Minjerribah’s aquifer, below which extraction should cease because it will cause environmental harm? What is the science to support it?
• Given the EPI only has a capacity of 22 ML/day – and Redlands needs 40 ML/day – where and how will Redlands (Including Southern Bay Islands) source water, without the supply from Minjerribah?

Also ask the authorities to:

• Consider reducing/suspending water extraction from Minjerribah until science can show what is an environmentally safe amount to extract, if any.
• Future-proof Redlands’ water supply so it is not reliant on the Minjerribah aquifer.
• Introduce water restrictions now for the Redlands.

Contact:

• The Hon Dr Anthony Lynham, Minister for Natural Resources, Mines and Energy nrm@ministerial.qld.gov.au
• Seqwater CorporateCommunications@seqwater.com.au
• Mayor Karen Williams karen.williams@redland.qld.gov.au
• Your local Redland City councillor  

Ask all mayoral candidates and division councillor candidates for the elections on 28 March what their position is regarding these questions and requests.

 Authorised by the SIMO Committee

Here is a link to the SIMO Facebook page

Redlands2030 – 8 February 2020

UPDATE 12 March 2020 – After the rain

It has rained recently. That’s really good news, especially on Minjerribah/North Stradbroke Island. But many will be surprised to know that much, much, much more rain is necessary to begin to replenish the island’s depleted aquifer – which supplies 60 per cent of the water consumed in the Redlands.

Meanwhile, we can rejoice that Leslie Harrison Dam (LHD) is now full. The combined capacity of the SEQ Water Grid has risen to 67.5 per cent. https://www.seqwater.com.au/dam-levels

With this very welcome reprieve in the drought, a window of opportunity now opens to allow Minjerribah’s aquifer and essential dependent ecosystems to begin to recover. 

The aquifer is at historic lows. It was not allowed to recover following the millennial drought of the early 2000s. Since then, the aquifer has only been further depleted by continuous pumping. The prudent course of action this time – if we are to ensure the future resilience of Redlands’ water supply – is to allow the aquifer to replenish. 

Rather than export 60 per cent of Redlands’ water needs from Minjerribah, we need to reduce that amount considerably for the time being. The Eastern Pipeline Interconnector (EPI) can deliver more of the City’s water. Of the 40 ML/day that Redlands uses, the EPI can supply 22 ML/day. And the LHD can deliver another 20 ML/day (the approximate capacity of Capalabah Water Treatment Plant). 

The use of these alternative and available water supplies in the Redlands would reduce the amount exported from Minjerribah to just that needed for the Southern Bay Islands (which for infrastructure reasons seem to be locked into Minjerribah’s water).

The total capacity of LHD when full is 13,206 ML, theoretically about 22 months’ supply (at 20 ML/day). But in practice, 22 months’ supply is not realistic because of evaporation losses and the need to maintain a preferred dam level. Low levels risk problems of water quality, including algal blooms.

How long the EPI and LHD can continue to supply the Redlands without Minjerribah water will depend on whether the rains continue. But any reprieve in pumping will help the aquifer and the island’s environment to recover.

For far too long everyone has assumed that Minjerribah’s water will always be there for the taking. There has been inadequate forward planning to avoid draining the aquifer to dangerous levels. 

This careless attitude is a legacy of when water extraction from the island began. But this attitude must stop, because the aquifer is not unlimited, and for years it has not been allowed to recover. 

It’s essential we have a long-term strategy for Redlands’ water security needs that doesn’t rely so heavily on Minjerribah’s aquifer. What are the options for future-proofing Redlands’ water supply without draining the aquifer on Minjerribah? For one thing, it is possible to increase the capacity of the EPI, and perhaps also the capacity of LHD. The small capacity of the EPI is a major flaw in the SEQ Water Grid.

It’s the right time to ask the authorities and the Council election candidates for their commitments to building water security for the Redlands and reducing reliance on Minjerribah’s aquifer.

Anyone who loves Minjerribah can help protect its environmental values by calling for these actions.

SIMO Secretary

Stradbroke Island Management Organisation (SIMO) is a community-based organisation on Minjerribah championing environmental, social and educational causes since 1978.