The Berejiklian government will review planned water restrictions for Sydney with the possibility that curbs on use will be tougher than presently detailed in the city's Metropolitan Water Plan.

Cabinet is expected to review the water plans next Monday to determine its response to plunging reservoir levels as the dry spell intensifies.

Cordeaux Dam is sitting on 40 per cent full, while the overall network of Sydney's dams is just below 54 per cent full. Credit:Nick Moir

Most of NSW has had very much below average rainfall for the past two years, and Sydney's April-May period is on track to be its second driest in 160 years, the Bureau of Meteorology said.

"The current depletion rate and drought conditions mean Sydney should expect formal water restrictions soon if there is no rain," a spokeswoman for Water Minister Melinda Pavey said.