Fears as Warragamba Dam nears capacity in NSW flood event

Sydneysiders are being warned to remain alert as Warragamba Dam nears capacity, after earlier fears the dam would spill following relentless rains.

The capital is expected to cop an estimated 90mm of rainfall through Friday, as the system that has caused devastating - and deadly - flooding across NSW Mid North Coast and Hunter regions moves further south.

More than 118mm of rain was recorded at Sydney Olympic Park in the 24 hours up to 9am on Friday, with 108mm at Belrose and 104mm in Parramatta.

Warragamba Dam - which is Australia’s largest concrete dam and services much of Sydney - had reached 97 per cent as of late Friday morning, with the catchment recording 55mm of rain in the 24 hours up to 9am Friday and 76.3mm in the past week.

WaterNSW had warned on Thursday - while the dam was at 96 per cent - that it was at risk of overflowing and spilling by Friday afternoon or early Saturday morning.

“The exact timing and volume of a spill will depend on catchment rainfall and the resulting inflow into the dam,” a statement read.

“Under the more likely forecast scenario, the dam would begin to spill later Friday or into Saturday morning.”

NSW Premier Chris Minns told ABC Radio Sydney on Friday morning that no evacuation alerts had been issued in the Hawkesbury region, though conditions could still change.

“The truth is 40 per cent of floodwaters don’t come over the top of Warragamba Dam, they come through the Colo, South Creek, Nepean and other river systems on the north of that river end,” he said.

The most recent update from WaterNSW, released later on Friday morning, said there was now less chance the dam would spill over.

“A spill at Warragamba Dam is now less likely after overnight rain over the catchment came in below the highest forecasts,” the statement read.

“WaterNSW will continue to monitor dam inflows and rainfall throughout the day and will keep the community updated on any expected impacts on Warragamba Dam.”

The dam was predicted to overflow after NSW residents were hit with a three-day barrage of rains in June last year.

The rains are not quite over yet for those in Sydney and NSW, with the Bureau of Meteorology’s Dean Narramore saying on Friday morning that severe warnings had been issued for regions from the Illawarra to the Snowy Mountains.

Some areas were tipped to receive six-hourly totals of up to 100mm.

The SES has warned of heavy rainfall extending further south to the Southern Tablelands and inland South Coast, which will affect Bowral, Braidwood, Bega, Katoomba, Goulburn, Nerriga and Captains Flat for the rest of Friday.