Members of the public having to line up to receive water at hydrants would be one of the severe consequences should Auckland's reservoir levels eventually drop below 15 percent, Mayor Phill Goff says.
Goff is warning more must be done to address the city's dire water shortage. Currently, Auckland's reservoirs are 44 percent full but would normally be about 78 percent full at this time of year.
The crisis hasn't quite reached the levels it did in 1994 when water reservoirs dropped to 32 percent.
Goff told The AM Show on Tuesday that council-controlled organisation Watercare needs to pull "every lever they can" to get more water into the city.
"If your lake levels fall below 15 percent then you're in the business of closing industry and people lining up for water at hydrants," Goff said. "I don't want to see that."
He said Auckland needed to build a "more resilient" water supply system in the future.
But he noted this was Auckland's first drought in 27 years, although the unpredictable impact of climate change means extreme weather may become more frequent, he said.
"The planning was catering for the growth [of Auckland], what the planning isn't catering for is a one-in-200-year drought - I'm not making excuses for that, I think Watercare has got to look at its strategic planning and they've got to do a whole lot of other things.
"We've got to plan accordingly," said Goff.
Restrictions that remain in place include not being allowed to wash cars or houses, or water lawns, sports fields and paddocks.
He urged Hamilton to "work as neighbours" and allow additional transfer of unused water from the Waikato River. He has met with officials in Hamilton to discuss Auckland's situation.
"If we don't get the rain we are in trouble," he said.
Watercare chief executive Raveen Jaduram told Newshub last month the situation was severe.
"We are working with the Waikato Regional Council, Hamilton City Council and Waikato-Tainui to be able to take another 25 million litres a day - that would be the capacity of our treatment plant," he said.
Desalination, or taking water from the ocean and making it drinkable, had also been touted as an option but Jaduram said that wouldn't solve the current crisis.
"Right at the moment our big focus is this summer, and unfortunately a desalination plant won't be able to be built in the time we've got," he told The AM Show in May.