The mayor of Cape Town, South Africa predicted in October 2017 that the city would run out of water by the following March. Since then, the date for what officials are calling “Day Zero” has shifted from April 21st, to April 12th, and April 16th. Today, May 11th, was another potential Day Zero — but the latest from the city is that the threat has been postponed to sometime in 2019. What gives?

In some ways, the shifting estimates are a good thing: they reflect how successful Cape Town has been at conserving its water. Now, no one’s washing their car, or hosing down sidewalks — and there are fewer leaky pipes. But the moving target also reflects the uncertain future of Cape Town’s water supply as the city enters the rainy season which, so far, hasn’t provided enough rain.

Day Zero is when the four million residents of Cape Town will be required to collect daily water rations: less than seven gallons (25 liters) for each person. Cape Town’s water comes almost entirely from rainfall, which is captured and stored in six major reservoirs around the city. But the city is currently in the middle of a three-year drought, so Cape Town’s reservoirs are dangerously low, at slightly more than a fifth of their capacity. That’s even worse than it sounds, since the last 10 percent of the water is hard to get at, like that last bit of liquid soap in a pump bottle.

“The sight of these empty dams have scared the whatsit out of everybody.”

In terms of conservation, “Cape Town has done fantastically in that, mainly because the sight of these empty dams have scared the whatsit out of everybody,” says Peter Johnston, a climate scientist at the University of Cape Town. The city put in place strict water limits; each person is allowed 13 gallons (50 liters) of water per day. For scale, that’s roughly the amount of freshwater that goes down the drain in three or four flushes of an older toilet, according to the USGS. People who use too much could be fined, and may have to agree to install a device that cuts off their supply if they use too much.

The city has also cut down on water waste by patching up leaky pipes and slowing the flow of water to a trickle. Lower water pressures mean less water seeps through cracked pipes — but it also reduces how much people use when they turn on their taps, Cape Town’s Executive Deputy Mayor Ian Neilson says. Together, the replacement pipes and the reduced water pressure save 13 million gallons (50 megaliters) daily.

It’s not just citizens — crops have had to make do with less water, too. The water quota set aside for agriculture is 60 percent lower than in pre-drought years, according to a city report. Once farmers hit their limit, they were cut off, says Janse Rabie, who represents the South African agriculture lobbying group Agri SA. “These strict water curtailments cost farmers dearly,” Rabie says in an email to The Verge. “It also had an enormous impact on farm workers (particularly seasonal workers) who could not be employed or had to be let go.”

The squeeze did help push back the date for Day Zero, though — far enough into the rainy season that city officials decided to call it off altogether. At that point, Neilson says, “It was completely unrealistic to base it on the assumption that there would be no rainfall.” The date would have shifted with every rainstorm, making it a bad benchmark for water thriftiness in the city.

“We’re going to have to get used to using less water on a permanent basis.”

So cancelling Day Zero doesn’t mean that there’s a reprieve, although that’s the message it seems to be sending. Reservoirs are still down to just one-fifth their regular capacity — but last week, water use rose. What’s more, calling off Day Zero could rob the warning of its strength the next time an official cautions that reservoirs are going dangerously dry. And it could happen again as rising global temperatures make droughts in the region more likely.

Even if new water sources — like desalinated seawater, groundwater, icebergs towed from Antarctica — do come online in the future, Johnston says that this culture of water conservation will need to continue, no matter what day it is. “We are careering towards disaster on all fronts — whether it’s agriculture, pollution, soil, water, pesticides. The human race is hellbent on destruction,” he says. “It’s a case of looking at the future and saying we’re going to have to get used to using less water on a permanent basis.”