Mullum’s future water supply still uncertain 

What is the best way to secure a long-term, reliable water supply for Mullumbimby?

This question has been batted around for years within Byron Council, but took on extra significance and urgency after the 2019–20 drought and bushfires, when the water supply for the town reached critically low levels.

Yet, more than three years on from the fires, the right solution is still the subject of debate within Council, and no action has been taken.

One point that most can agree upon is that Mullumbimby’s current water source, the ageing Lavertys Gap weir in Wilsons Creek, is not a viable long-term option in its current state.

Council reports show that demand for water in Mullumbimby is basically equal to the amount that the weir can sustainably supply in normal rainfall conditions.

With the town’s population forecast to grow significantly over the next decade, and climate change putting paid to any reliance on consistent rainfall, there is a very real risk the town could run out of water if an alternative source is not found.

It is predicted that, if Mullum continues to rely on Lavertys Gap without modifications, demand would exceed supply by 37 megalitres per year by 2050.

Council staff say that Lavertys Gap weir is having a significant negative impact on the surrounding environment, and that the water treatment plant it flows through is no longer up to the task of providing a quality water supply.

The question of what to do about this remains a highly-vexed one.

Council staff argue that Mullumbimby should follow the rest of Byron Shire, and move onto the supply from Rous Water, the organisation responsible for water management across the region.

They point out that the infrastructure already exists to make this happen, in the form of an emergency line that the town made use of in 2019, and that this is the only viable way of guaranteeing a long-term water supply for the town.

But the members of Council’s Water and Sewer Advisory Committee disagree as do Water Northern Rivers (WNR).

The Water and Sewer Advisory Committee do not believe that Rous Water can be relied upon to deliver an environmentally sustainable water supply into the future, pointing to the organisation’s periodic support for a dam at Dunoon which, if constructed, would flood huge areas of farmland and native habitat.

‘Rous Water is an entity unto themselves, and I don’t feel that they have environmental considerations high on their agenda,’ said Greens Councillor, Duncan Dey, who is a member of the committee as well as a professional hydrologist.

Cr Dey and his fellow committee members argue that modifications can be made to Laverty’s Gap weir to help it form part of a sustainable supply. This includes fish ladders, environmental flows and building a large water storage tank to back up the weir. 

A broader supply solution also includes other water sources, such as the groundwater system at Tyagarah, and improved rooftop water harvesting.

‘Within that committee, there’s real expertise, and we all agree that diversity of water sources is a really healthy model,’ Cr Dey said.

‘Having a singularity of sources is not a good plan.’  

Water Northern Rivers point out that a connection of Mullumbimby to the Rous Water grid and disconnecting the Lavertys Gap supply ‘would be a retrograde, unsafe, expensive and unpopular step’.

‘The Dunoon Dam (DuD) will probably not go ahead due to numerous insurmountable problems,’ said WNR spokesperson Nan Nicholson. 

They highlight the recognised and significant Indigenous cultural heritage sites that would be drowned as well as ‘the loss of highly significant natural heritage, especially koala habitat and the Endangered Ecological Community of Lowland Rainforest (part of the last one per cent of the Big Scrub).’

Cost blow out – $220M to $815

The increasing, and some say prohibitive, cost estimates for the dam are also another issues raised by WNR. 

‘The cost of the dam has increased from $220 million, as modelled by Rous’ consultant Hydrosphere, to $815 million according to the DPE, if additional connections as made,’ points out Ms Nicholson. 

‘The state government is unlikely to finance the dam which leaves it to the rate payers to bear the huge burden of rate hikes. Mullumbimby residents would be paying through the nose to enable unrealistic growth in Ballina and Byron coastal zones.

‘The Strategy’s cost/benefit analysis of the dam found no economic benefits over costs when climate modelling was applied.

‘There is very poor social licence for the dam and if it went ahead there is likely to be severe social division which would reflect poorly on Byron Council. The residents of Mullumbimby have been in the forefront of opposition to the DuD and this would be a betrayal and an unfair financial burden.

‘If Mullumbimby becomes committed to Rous’ water it would leave the town with an even greater water problem.  Byron Shire Council needs to increase diversity of supply and reduce demand on Rous’ water.  Connecting Mullumbimby to the Rous grid would do the opposite.’

At this stage, the two sides appear to be at an impasse.

A special workshop is planned before it goes to Byron Council in late April or May.