Cape Town is bracing for an unfortunate distinction: becoming the first major city in the world to run out of water.

Severe drought over the past three years coupled with population growth means the city and its residents are bracing for “Day Zero”, the day taps throughout the city will officially run dry. Many of the factors leading to Cape Town’s predicament are specific to the city, but climate change also plays a significant role. While Cape Town may become the first city to run out of water, it will likely be the first of many as climate change continues to impact the world in unpredictable ways.

Understanding the catastrophe of Day Zero

Other than breathable air, water is probably the most necessary daily need for human life. But the reservoirs surrounding Cape Town are dangerously low. When their collective volume hits 13.5 percent, all taps to the city will be turned off and 200 emergency water collection points will take their place.

This is Day Zero and it is currently estimated to come on May 11.

Cape Town is a city of nearly 4 million people, and never before has an entire city, let alone a city of this size, run out of water. As a result, trying to grasp exactly what this will mean if Day Zero does come to pass is difficult. The city government is doing its best to prepare for the worst, but it is understanding what that is that is proving elusive.

To start, 200 water stations for 4 million people is not very many. If evenly distributed, that leaves each water station servicing 20,000 people a day. That means every water station will have to serve more than 800 people an hour. Each person will only be allowed 25 liters (6.6 gallons) of water per day. The current water rations allow double that amount, and even then many people are struggling to keep within that limit. Water hoarding has become a thing, which could help some families in the long run but also hints at how easily social unrest could develop when water becomes truly scarce and strictly allotted.

Then there are the economic costs. Productivity is bound to go down as people are forced to divert their time and energy towards water collection. Business such as restaurants that rely on water will be forced to temporarily close. Tourism, a major part of the local economy, will likely suffer as well. Cape Town is already facing a budget shortfall of $142 million due to the water crisis; if Day Zero actually happens, that number is likely to sharply increase.

Finally, there are health risks of running a city on no water. Hospitals and schools will still have water supply, albeit at a reduced rate. But overall sanitation will take a hit from the reduction of water access. City officials have begun warning about what could be to come, as water borne and sanitation diseases become more prevalent.

Climate Change & Inequality

Despite sitting on a peninsula surrounded by the Atlantic Ocean, Cape Town is in a relatively dry region. Unlike most of the country, its rainy season falls in the winter rather than the summer, starting in late May and lasting through August. The dry climate and encroaching threat of climate change, highlighted by an especially bad drought in 2005, led the city to make water conservation a primary goal. But the droughts brought on by El Nino that rocked all of Southern Africa starting in 2015 hit the city particularly hard. Even as other countries in the region have bounced back, Cape Town remains dry and the landmark conservation efforts enacted years have proven to simply not be enough.

The current droughts are estimated to be a 1 in 400 year event, meaning the Western Cape has likely never seen a drought event of this magnitude since Europeans first came ashore. As Dave Chambers noted in The Independent, never has the region seen three years of drought this severe. Although the 2005 water crisis came as a result of three successive years of drought, in that case cumulative rainfall was only 25 percent below normal. This time around, it is a whopping 55 percent.

That said, there are other factors compounding the drought to make this water crisis so severe. Namely, South Africa has one of the highest levels of economic inequality in the world. Despite being a world renowned tourist destination and a an economic powerhouse within South Africa, the legacy of Apartheid still haunts the country’s second largest city. Cape Town has worked hard to close the gap of basic service delivery in recent years, but thousands of households in the city still do not have access to running water or connection to the sewage system inside their homes. The divide between who has access and who does not falls largely on racial and socio-economic lines. As a result, the focus in recent years has been on water conservation rather than building new infrastructure, even as more and more households come on the grid and draw from the same water sources.

The specific factors leading to Cape Town’s troubles may be unique to the city but it is also a scene that will likely unfold elsewhere in Africa.

The combination of the pressures of climate change and economic inequality threaten more than just Cape Town in the coming years. Nairobi and Accra are two others cities undergoing water rationing as their city populations grow but the water infrastructure has not. Severe droughts, once a phenomena that occurred every few decades are now becoming commonplace. Those most likely to be hurt by dwindling supplies are also those who are least able to cope with these changes. Oddly enough, they are also the ones who often have limited access to water to begin with.

It is possible that Day Zero will not come to pass in Cape Town. A recent drop in agricultural water use pushed back the estimated date by a month into May, when hopefully the first rains of the season will come. That may be enough to stave off a complete water shutdown. But even if that happens, what is happening in Cape Town now serves as a lesson for what more and more cities will have to deal with in the future as climate change impacts the livability of regions settled long ago. The time to plan is now, and not when another water crisis is upon us.