Cities Stare Down ‘Day Zero’ as Reservoirs Go Dry

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In Mexico City, more and more residents are watching their taps go dry for hours a day. Even when water does flow, it often comes out dark brown and smells noxious. A former political leader is asking the public to “prioritize essential actions for survival” as the city’s key reservoirs run dry. Meanwhile, 2,000 miles south in the Colombian capital of Bogotá, reservoir levels are falling just as fast, and the city government has implemented rotating water shutoffs. The mayor has begged families to shower together and leave the city on weekends to cut down on water usage.

The measures come as a so-called heat dome sitting atop Mexico is shattering temperature records in Central America, and both Central and South America are wasting beneath a drought driven by the climate phenomenon known as El Niño, which periodically brings exceptionally dry weather to the Southern Hemisphere. Droughts in the region have grown more intense thanks to warmer winter temperatures and long-term aridification fueled by climate change. The present dry spell has shriveled river systems in Mexico and Colombia and lowered water levels in the reservoirs that supply their growing cities. Officials in both cities have warned that, in June, their water systems might reach a “Day Zero” in which they fail altogether unless residents cut usage.

In warning about the potential for a Day Zero in the water system, both cities are referencing the famous example set by Cape Town, South Africa, which made global headlines in 2018 when it almost ran out of water. The city was months away from a total collapse of its reservoir system when it mounted an unprecedented public awareness campaign and rolled out strict fees on water consumption. These measures succeeded in pulling the city back from the brink.

Six years later, Cape Town stands as a success story in municipal crisis management, but experts say its playbook will be hard for Mexico City and Bogotá to replicate. Instead of focusing primarily on changing public behavior, these cities will need to make big investments to improve aging infrastructure and shore up their water supplies. How they fare in these endeavors will in turn inform future efforts to make the world’s fast-growing cities resilient to increasing climate volatility.

“The bigger question, and what’s relevant for other cities, is now that we’ve experienced this, what can we do going forward to make sure that this doesn’t happen again?” said Johanna Brühl, a water expert at the nonprofit Environment for Development in South Africa who has studied Cape Town’s water crisis.

Coining the very phrase “Day Zero” was part of Cape Town’s solution to a water crisis that many officials had seen coming for years. As reservoir levels fell between 2015 and 2017 amid a drought, city leaders released dozens of statements urging residents to reduce water usage, but no one paid much attention. Only in early 2018, when officials started talking in increasingly apocalyptic terms about a collapse of the municipal water system, did residents — and international media outlets — start to pay attention.

The city rolled out a set of measures to enforce cuts, including a tariff system that charged more thirsty users a higher price per gallon plus a door-knocking campaign to shame the biggest water hogs. But it was the rhetoric around Day Zero that seemed to be the most effective tool to slash water usage, experts who studied the crisis told Grist. When the local government warned that residents would have to pick up buckets of water from public collection points managed by the military, consumption plummeted. The effort to stave off a water crisis began to look like a grassroots movement, with residents sharing conservation tricks like flushing the toilet with water captured from the shower.

By April 2018, water usage had fallen to about half of what it was three years earlier, a decline that astonished even city officials. As consumption dropped, the city pushed the estimated date of the apocalypse out by a few days, then a few weeks. When a big rain arrived in the early summer and began to refill the reservoirs, the government turned off the countdown altogether, declaring the crisis at a temporary end.

“The big take-home point for any city in terms of navigating that kind of crisis is just to change the culture and to get the needle moving in the right direction,” said Eddie Andrews, the deputy mayor of Cape Town, who was a city council member during the Day Zero affair. “Culture is really important — making sure that you remain on message.”

Political leaders in Mexico and Colombia…