The Wellington Regional Council says a key water treatment system is just days away from closing if there is no rain.
Wellington's Water Operation's Manager Noel Roberts said the region had had showers in recent days, but not enough to improve the situation.
He warned the Wainuiomata Water Treatment Plant may have to close within a week.
Mr Roberts said people needed to ease back on their water use and warned garden watering restrictions may be imposed.
The Kapiti Coast District Council has also announced today the water supply for Waikanae, Paraparaumu and Raumati is now 100 percent bore water due to the low level of the Waikanae River.