Cape Town is running out of water: Are U.S. cities next?

Sometime in late May or early June, Cape Town, South Africa—comparable in size to the city of Los Angeles—is predicted to become the first major world city to completely run out of water. When that happens, authorities will cut off taps to all homes and most businesses, meaning that a population of 4 million people won’t have access to running water.

No U.S. city currently faces a water problem of this magnitude, but the country isn’t immune to water scarcity either. As cities grow, populations rise, and the effects of climate change become more apparent, urban centers throughout the U.S. are more at risk of water shortages. To understand just what is at stake, we take a look at which U.S. cities are most threatened by water stress and what could happen when the taps run dry.

Why Cape Town is running out of water

For a modern metropolitan city that’s won a prestigious international award for its water-conservation policies, the current situation in Cape Town might seem inconceivable. Just four years ago, the city’s six major reservoirs—which hold up to 230 billion gallons of water—were full. As of January 29, 2018, NASA reports that those reservoirs are at just 26 percent, with the largest reservoir at only 13 percent capacity.

The drastic change is due to a devastating three-year drought and the region’s near-total reliance on rainwater. On average, Cape Town receives about 20 inches of rain each year. In 2015, the city received 12 inches, and the following year the weather station at Cape Town’s airport recorded only eight inches. It seemed impossible that the drought could get worse, but in 2017 it happened: Cape Town recorded just six inches of rain last year.

Piotr Wolski, a hydrologist in the Climate Systems Analysis Group at the University of Cape Town, put those figures into perspective, concluding that back-to-back years of such little rainfall typically happens just once in every 1,000 years. Throw in a booming population and a lack of new infrastructure to handle the crowds, and you’ve got today’s disaster.

Courtesy of NASA Earth Observatory

Which U.S. cities are at risk

Cape Town isn’t the only city in the world faced with water challenges. According to the Nature Conservancy’s first global survey of cities’ water supplies, places like Mexico City, Tokyo, and Delhi are some of the most water-stressed cities in the world. While no city has reached “Day Zero,” the day when the taps will run dry, many of Mexico City’s 21 million residents only have running water for part of the day. Officials in Melbourne, Australia, report that they could run out of water in about a decade, and in 2015 in São Paulo, Brazil, the city was down to less than 20 days of water supply.

AP Photo/Damian Dovarganes

Only one U.S. city makes the top 10 of the Nature Conservancy’s water-stressed list: Los Angeles at No. 9.

In myriad ways, the water situation in Los Angeles is drastically different than what’s unfolding in Cape Town. Like Cape Town, LA gets its water from rainfall, but unlike the South African capital, LA also benefits from precipitation in the surrounding mountains and more natural groundwater sources.

Still, LA loses about 80 percent of its water into the Santa Monica Bay and has been severely affected by drought and wildfires over the past five years. (Read more about the Los Angeles water situation over here.)

Elsewhere in the West, low rainfall and a growing population both put stress on existing supplies, not to mention 90 percent of the water extracted is consumed by agriculture. Urban areas—although not as large as the cities on the coast—are booming, and 86 percent of all Westerners live in or near cities. This means that in places like Denver; Las Vegas; Salt Lake City; Phoenix; Tucson, Arizona; and El Paso, Texas, more people than ever are using a finite amount of water.

Pay attention to the U.S. Drought Monitor and a troubling picture emerges: After record-breaking droughts in 2013, 2014, and 2015 in California and much of the West, that same area is abnormally dry. Parts of California are once again experiencing drought, while two-thirds of Arizona and three-fourths of New Mexico are facing severe or extreme drought. Crucial rivers like the Rio Grande—which supplies water to much of the Southwest—are measuring at the lowest levels in 70 years.

A lack of rainfall over a period of a few years doesn’t necessarily mean U.S. cities will face the kind of crisis now playing out in Cape Town. But like South Africa, the U.S. is becoming increasingly reliant upon precipitation for its water supplies. Once-abundant aquifers are running dry, and it will take thousands of years to replace them.

North America’s largest aquifer is called the Ogallala, or High Plains aquifer, and it covers 174,000 square miles over portions of South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico, and Texas. This groundwater serves the most productive farmland in the U.S.—to the tune of $35 billion in crops annually—and it’s disappearing.

Photo by Aaron Ontiveroz/The Denver Post via Getty Images

Irrigators using the Ogallala aquifer are pumping out the groundwater faster than rain can refill it, and over the past six years, water levels have declined twice as fast as the previous six decades. Draining the aquifer doesn’t just affect what lies beneath the surface; over-pumping has dried up 358 miles of surface rivers and streams in eastern Colorado and western Kansas and Nebraska.

It’s not just Western cities that are at risk of water shortages. Miami, which receives 60 inches of rain each year and has a plentiful coastline, isn’t the first metro area that comes to mind when you talk about water stress. But rising sea levels mean that seawater threatens to contaminate the city’s freshwater supply, both from floods above ground and from the porous limestone underground that can contaminate drinking-water wells. Thanks to saltwater contamination of the Biscayne Aquifer, the city of Hallandale Beach, just a few miles north of Miami, has had to close six of its eight wells.

What could happen when cities run out of water

It’s not inevitable that Cape Town’s Day Zero will happen. Officials originally predicted that Day Zero would come on April 21, then adjusted it forward to April 12, before recently pushing the date back further to early June thanks to agricultural cutbacks.

The city has reduced its total daily consumption of water from 1 billion liters of water per day in 2016 to about 526 million liters per day today. Catastrophe might also be avoided if Mother Nature cooperates; the rainy season usually starts in May, although forecasters warn that if the drought continues, this year’s rain might not be enough to replenish the reservoirs.

If Day Zero occurs, residents will have to go to roughly 200 collection points to get about 6.5 gallons of water a day. The logistics are predicted to be astoundingly difficult, especially because it will be impossible for people to carry all of the allocated water home by hand. If every family sends one person to fetch its water allocation, about 5,000 people will arrive at each water collection site each day.

Officials are concerned that the limited number of sites mixed with Cape Town’s already comparatively high murder and robbery rates means that the possibility of civil unrest is high.

AP Photo

South Africa’s large disparity between the wealthy and the poor—it’s among the most unequal countries in the world for income distribution—also raises concerns. According to the New York Times, wealthy residents have installed water tanks in their yards, paying about $4,200 to become water self-sufficient. The city’s poorest residents, and especially those without cars, will be forced to choose between long treks to get water and the everyday necessities of work and child care.

And while Cape Town plans to keep water flowing to key facilities like hospitals, an extended water shortage will have a devastating effect on the city’s tourist-driven economy.

No major U.S. city has run out of water, and it’s unlikely that the exact combination of drought and sluggish government response in Cape Town would play out in the same ways in the U.S. But twice since 2007 California has declared a statewide emergency due to drought, and large cities such as Fresno and Sacramento spent years with nearly all of their land in extreme drought.

Smaller cities in the U.S. have run out of water before. East Porterville, a small town near Bakersfield, California, with about 7,000 people, saw hundreds of wells go dry in 2014. State officials trucked bottled water to city residents and forced them to go without showers, and locals used gray water to flush toilets, all at a cost of $650,000 per month. East Porterville did not regain water until late 2016, when a neighboring town extended its water supply system.

Experts believe that climate change and growing populations mean that the crisis in Cape Town inevitably will repeat itself on a global level. Droughts are likely to become more frequent and more severe, while warmer temperatures will cause what water is left to evaporate more quickly.

Whether U.S. cities run out of water in the future will depend on what governments and residents do now to prepare. Diversifying local water supplies, conserving the water we have, and investing in water-recycling and stormwater-capturing technologies can all delay disaster.

But with water prices on the rise and increasingly frequent natural disasters that will further stress our water supplies, there’s no question that water scarcity could become the key issue of the 21st century. Even in the United States, the taps may not always flow.