The Thomson Dam spillway overflowing last year.Credit:Nine News
“If the next six months are dry enough that the catchment dries out,that makes it harder to fill in the second half of the year because rainfall is less likely to translate into significant runoff,” he said.
“People often underestimate the importance of how much water is in the catchment and how wet it is.”
Victoria’s desalination plant has not been in operation since April this year due to the high dam levels,with no water orders expected until the middle of 2024.
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The desalination plant has contributed 455 billion litres to Melbourne’s supply since 2017,around a quarter of the city’s water needs.
“It takes more than one year of drought to get Melbourne into water shortages,” said Khan.
“But troubles come if you have a July to November period that’s not wet. Then it could get down to 75,even 60 per cent[full]. That’s when people get more concerned.”
Wenju Cai,chief research scientist at the CSIRO and an expert in El Nino-La Nina,said that El Ninos brought hotter and dryer conditions to south-eastern Australia.
It’s still too early to tell,but Cai said that this El Nino could be a weaker pattern,which means that its effects can last longer than one year.
The Thomson Dam in 2008.Credit:Craig Abraham
The El Nino in 2018-19 was weaker and corresponded with the devastating Black Summer bushfires in 2019-20.
“Those consecutive dry conditions in the Pacific affected the cumulative rainfall and also made the temperature oppressively high before the fires could occur,” he said.
A Melbourne Water spokesperson said water storages were almost at the same highs experienced last year,putting the city in a good position ahead of summer.
“Despite our strong water storage levels,under El Nino weather conditions we know storages can drop quickly,by as much as 20 per cent in a single year,” they said.
“With September rainfall over our four major harvesting catchments 43 per cent below the last 30-year average,it is likely that we’re already experiencing the effects of El Nino,so we ask Melburnians to continue using water wisely and make every drop count.”
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