The Kurnell desalination plant which has sat idle for the past five years may need to be switched back on if Sydney’s dam levels continue to fall.

Water levels at storages supplying the Sydney metropolitan area are sinking amid a lack of rain and rising consumption.

The total storage levels for the Sydney region are running at about two-thirds full, with the desalination plant set to be turned on to supplement the water supply when capacity drops to 60 per cent, according to WaterNSW.