Tide’s out and not coming back any time soon

New modelling by the NSW governmen­t warns that the likelihood of longer-duration droughts is significantly higher than previously thought.

Nick Bailey and his family on their property 'Big Panuara', 40kms south west of Orange. Children are (oldest to youngest) Harriet, Polly, Abbey and Sandy (baby boy). Picture: Kirsten Cunningham

New modelling by the NSW governmen­t warns that the likelihood of longer-duration droughts is significantly higher than previously thought, with a greater chance of dams near major towns such as Dubbo, Orange and Bathurst remaining empty or close to empty for extended periods.

But the “conservative” modelling, commissioned by the Depart­ment of Planning, Industry and Environment, paints a varied picture across the state — with some regions near Forbes and Parkes likely to have a “reasonable level” of water security and the recent drought described as “not unique”.

The government will use the modelling to decide on thousands of droughtproofing infrastructure projects after the devastating droughts last year, the worst in decades, which led to the death of hundreds of thousands of fish and acrimony among irrigators.

Overall, the documents predict that climate change will mean not only higher temperatures but more hot days, droughts occurring in closer succession, changing rainfall patterns and significant water shortages.

“Our new climate modelling results indicate that, with climate change, there may be more times when the amount of water we currentl­y have available to share cannot meet all of the needs of water users,” the report says.

“Under the future climate change scenario, the run-off that comes from rainfall and fills the dams may not happen as often, or we may not see the same amount of run-off as we currently do.”

Until now, water management decisions in NSW and across the Murray-Darling Basin have been based on historical records of climate­ conditions going back to the 1890s — about 130 years of rainfall, temperature and evaporation data, leaving planning decis­ions based around a small number of historic droughts.

The new “palaeoclimate” data — reconstructed from sources such as tree rings, cave deposits, river sediments and coral growth — provides 500 years of climate records to predict the likelihood of droughts and floods.

The modelling is being used by Water Minister Melinda Pavey to shape regional water strategies over the next 20 to 40 years — which could dramatically affect the market value of water licences.

Billions of dollars in licences and infrastructure in the Murray-Darling Basin are at stake, as current allocations are based on more recent rainfall records.

“These climate scenarios will not necessarily eventuate, but they give us an idea of the possible climate risks and allow us to begin planning to mitigate these risks if they arise,” Ms Pavey said.

 

If these projections eventuate, inflows into dams in the Macquarie-Castlereagh region of central­ NSW could decrease up to 50 per cent by 2070.

That’s bad news for farmers such as Nick Bailey, 38, who breeds prime lambs on 6070ha at Panuara, south of Orange, and has just emerged from one of his worst years to one of his best.

Last year drought wiped out the crops he grows on another family property and he had to borrow more than $1m to feed his animals. “We just made the decision that we didn’t want to lose our core breeding flock and we were feeding over 10,000 ewes,” he said.

“It was costing us $10 a head per month, and we fed them for six months straight. We had to extend­ our overdraft line of credit many times.”

This year, most of his dams are close to full. However, like many other farmers, Mr Bailey is tackling climate change head-on.

“We’re seeking varieties of grain and crops that are more tolera­nt to drier conditions,” he said. “And we’re lucky in our district, droughts aren’t a long-term issue. We’ll miss a season or two and then we’ll get a break.”

But the new government model­ling suggests that run of good fortune might not last.

In the Macquarie and Castlereagh rivers region, which takes in Orange, Dubbo, Bathurst and the internationally recognised Macquarie Marshes, droughts are predicted to occur in closer succes­sion, with less time to recover in between.

The frequency of a severe, once-in-a-decade drought may increase by 22 per cent.

There is also a 2 to 3 per cent probability of droughts similar to the 2017-2020 drought — one of the worst on record — any given year, potentially leaving Burrendong Dam at less than 5 per cent full “for extended periods, with sustained pressure on town water supplies”, the regional water strategy documents read. Burrendong is one of the largest inland dams in the state, with a capacity three times that of Sydney Harbour.

Temperatures in that region are expected to increase by an averag­e of 0.7C by 2030 and 2.5C by 2070, the modelling shows.

The NSW government was warned as early as December 2013 that reliable water supplies in parts of the state could plunge by almost a third by 2030.

While plentiful rain this year has filled dams, there were concerns only last August that Tamworth, Orange, Bathurst and Dubbo could run out of local water. A worsening situation, at the time, had already forced the state to spend $15m delivering water by truck to smaller towns.