Sydney needs ‘a metre of rain’ to break drought as dam levels extend dive
By Peter Hannam
Updated October 23, 2019
Sydney’s dam levels are falling so quickly the city would need the equivalent of a metre of rain and a major deluge to break the dry spell.
Details of the state of Sydney’s catchments were circulated to government agencies this month as NSW braces for increasing stress on water supplies, particularly across the northern Murray-Darling Basin.
“It will take approximately 1000 millimetres of rain to fall over the course of a year in order to break the current drought in Greater Sydney, including an intense rain event of 200 millimetres over 1-2 days,” the government document states. “The annual average is 850 millimetres.”
Sydney’s dams are 48 per cent full, down more than 10 billion litres over the past week. The weekly drop of 0.4 percentage points would have been more without the 250 million litres being produced daily by the city’s desalination plant.
“Greater Sydney is in drought and dam levels are dropping faster than they have in decades,” a spokeswoman for Sydney Water said.
“This … is around 50 per cent greater than the Millennium Drought,” she said, adding that storage levels had sunk from 90 per cent to below half full in about two years.
How our dam’s levels have changed since 1984.
Governments have been scrambling to respond to a sharp reduction of rainfall even as evaporation rates have increased with record temperatures.
In NSW during the first nine months of 2019, rainfall has been half the average while daytime and mean temperatures are running at the hottest on record.
“The Bureau of Meteorology’s climate forecast indicates no foreseeable signs of reprieve from current drought conditions, with warm and dry weather predicted,” the Sydney Water spokeswoman said, citing bureau outlooks.
“Based on these forecasts, the drought is therefore unlikely to break within the next year.”
Sydney’s warm, dry spring may see one of the hottest days in recent years on Friday, when the mercury is tipped to climb to 33 in the city and 37 in the west. There’s no rain on the horizon in the coming seven days.
Sydneysiders use about 210 litres of water a day, or about 30 per cent more than in Melbourne, said Ian Wright, a senior lecturer in Environment Science at Western Sydney University. Towns such as Orange in central-west NSW have cut usage to about 133 litres a person each day.
While many inland towns have moved to level 4 or higher restrictions, Sydneysiders have only had to cope with level 1 curbs since June.
Residents, for instance, can only use a hose – which must be equipped with a trigger nozzle – before 10am and after 4pm each day.
Sydney Water said its “Love water, don’t waste it” campaign was having some success.
For the first nine months of the year, Sydney used 414.1 billion litres, with demand down 7 per cent from the 444.7 billion litres consumed for the same period last year.
That reduction “made a big difference to Sydney’s water security”, the spokeswoman said.
NSW Water Minister Melinda Pavey said Sydney’s restrictions were already “equivalent to the level 2 water restrictions we experienced during the Millennium Drought. The trigger point for level 2 water restrictions [this time] is 40 per cent capacity for the Sydney catchment.”
Labor’s water spokesman Clayton Barr said “there is a growing concern across parts of the Sydney water network, and the state more widely, about how water is being handled and preserved”.
Mr Barr said he recently met community groups at Cataract Dam, the largest dam in the Macarthur Region, who were worried that levels had dropped from 90 per cent to under 30 per cent in just two years.
Peter Hannam writes on environment issues for The Sydney Morning Herald and The Age.