SCU professor Peter Coombes urges caution on harvestable water rights

Water expert highlights challenges in monitoring irrigators as North Coast MPs talk up deeper dams

Southern Cross University Professor of Water Resource Engineering Peter Coombes. The SCU Associate Dean says changes to harvestable rights need to take into account the effect on the environment.

With dam talk at a post-flood high, a senior hydrologist at Southern Cross University discusses the ‘fraught’ issues surrounding our most precious resource.

Acknowledging the increased attention water rights get following times of great rainfall, Professor of Water Resource Engineering at SCU Peter Coombes says his ‘rule of thumb’ has been to think back to the dry times.

With North Coast MPs talking up increasing dam levels and the State Government re-examining harvestable water rights, or, the run-off farmers can capture, Mr Coombes said it was important changes took into account what happens “when you have below average rainfall”.

He said the great challenge has always been balancing the interests of irrigators and the environment and in times of drought or low flow there needed to be assurances landholders would release water to maintain the viability of natural watercourses.

“You can see how fraught this is. It can go horribly wrong – and it has in the Murray Darling – but you can put governance processes in place that says if you are in a (period of) low flow, the environment comes first.”

“Because when we get through it we still need a healthy waterway.”

A Natural Resources Access Regulator officer casts a depth sounder which determines the maximum depth of a dam.

Mr Coombes has spent his life dedicated to understanding and shaping our use of water, serving as chief scientist for the Office of Living Victoria as well as co-authoring the Prime Minister’s Science, Engineering and Innovation Council assessment of Australia's water future.

Now an Associate Dean at SCU, Mr Coombes highlighted the importance of getting the governance around “complex” water allocations right, so as not to repeat mistakes of the past.

While debates over water were often polarising, Mr Coombes said it was important for people to engage with the issue and he indicated there could be opportunities to harvest more water provided environmental impacts were considered and irrigators were monitored appropriately.

At the moment understanding just how much water is being harvested is challenging and Mr Coombes agreed that without water gauges, there was no way of knowing without undertaking detailed hydrology models.

Even analysis being undertaken for the NSW government’s review into harvestable rights was being done using modelling because there was “no other way” in a catchment without gauges.

“You can get real evidence based on the gauges but the problem is … we would need a lot more gauges to be precise about the impact,” he said.

NRAR officers inspecting farm dams on the Coffs Coast.

Another issue brought up through the government’s review has been to allow landholders to dam third order streams, which are streams which flow higher in the catchment.

While this has traditionally been off-limits to farmers, Mr Coombes said any push to “systematically” dam those streams would need careful consideration given the “cumulative” effects which occurred.

Those effects would not just be felt at an environmental level, but by all downstream landholders.

“The upper catchments drive the behaviour of the entire catchments further downstream,” he said.

“The consequences of changing things in the upper catchment are quite substantial.”

There will be an online webinar on the coastal harvestable rights review on April 7, visit Industry NSW’s website for more details.