An Illawarra firefighter's photos of old timber bridges in the Cataract catchment area have shined a spotlight on the dam's rapidly dwindling water levels.
Multiple fire crews were called to a grass fire at Cataract, in a restricted area above the Illawarra Escarpment, about 11am on Saturday.
While there, NSW RFS firefighter Philip Robertson took some snaps of the upper reaches of the drought-affected dam and posted them on Lost Wollongong's Facebook page.
"The water levels are so low it has uncovered some old timber bridges from long past," he wrote.
Fellow Lost Wollongong member Louise Piazza then shared an image she said was taken of one of the bridges back in May. The photo shows the structure fully submerged in water.
Cataract Dam was taken offline for drinking water in September after falling to just 27.1 per cent of its capacity.
It has since dropped further to 26.1 per cent, which represents 25,394 megalitres, from a capacity of 97,190ML.
The total dam levels for the Greater Sydney catchment were at 45 per cent on Sunday as the prolonged dry spell takes a toll.
The Illawarra's main water supply comes from Avon Dam, a 10.5-square-kilometre body of water west of Wollongong, which currently sits at 43.6 per cent capacity.
What happened to Cataract Dam?
In September, the Illawarra Mercury asked WaterNSW what had happened since 2017 to cause the water level in Cataract Dam to sink from an average of 87.5 (2017) to 43.1 per cent (2018).
"WaterNSW has used Cataract Dam more than other Upper Nepean storages recently to allow for essential maintenance and upgrade works at Pheasants Nest weir," the spokesman said.
"Greater Sydney' dam storage network is configured in such a way that supply can be adjusted to distribute demand between Upper Nepean storages, and to allow for important maintenance work to ensure the network is operating at full capacity."
Supply to the Macarthur plant can be sourced from any of the four Upper Nepean storages: Cataract, Cordeaux, Avon and Nepean.
Dam levels on Sunday
- Warragamba Dam 45.9%
- Woronora Dam 36.4%
- Avon Dam 43.6%
- Cataract Dam 26.1%
- Cordeaux Dam 38.2%
- Nepean Dam 50.4%
Tighter water restrictions
From December 10 people in Macarthur will only be able to water their gardens or wash their car with a watering can or a bucket, and only between 4pm and 10am.
Pools can only be filled for 15 minutes a day, and only with a spray nozzle on the hose.
Hosing hard surfaces is not permitted, but commercial car washes are allowed.
"We're experiencing one of the most severe droughts on record and we expect introducing Level 2 restrictions to save 78.5 gigalitres of water per year," Premier Gladys Berejiklian said.