Curious Cook: The myth of infinite water, part 1

Many years ago, I was in Barcelona, on Spain’s northeastern coast, when I first understood – really understood, in my gut – what water scarcity means. I was staying in a hotel on a work assignment, and caught in a drought that had gripped Catalonia for months. The city’s reservoirs had dropped to 21% of capacity. Restaurants served meals on paper plates because dishwashers were banned. Hotel rooms had polite laminated cards asking guests to limit showers to three minutes. In the news were plans for rationing water. And around the corner was the Mediterranean Sea, blue and infinite, stretching to the horizon: 3.75 quintillion litres of water, so close I could taste the salt on the wind, and not a single drop I could drink. That is the paradox at the heart of our relationship with water. We live on a blue planet. We see it from space, we dance in the rain, and we take water for granted every time we turn on a tap. But the real statistics tell a story that is deeply uncomfortable. Of the 1.386 billion cubic kilometres of water on Earth, 97.5% is ocean, and undrinkable. Of the 2.5% that is freshwater, two-thirds is locked in glaciers and ice caps. What remains is mostly buried in deep underground aquifers that recharge on geological timescales – millennia, not years or even decades. Available surface freshwater is only roughly 0.3%. And the water we can actually use, the water in rivers and lakes and accessible aquifers, the water that grows our food and fills our reservoirs and comes out of our taps: added up, that makes roughly 0.007% of the total. The Earth has a finite supply of water that only recycles itself; not renews. — CHUCK/Pexels If our entire planet’s water were a hundred-litre bathtub, the drinkable, accessible fraction would be about one teaspoon. And here is the part nobody told you at school: there is no new water. None. The total volume on Earth has been essentially the same for four and a half billion years, cycling endlessly between ocean and atmosphere and land, evaporating and falling and running back to the sea. The Earth’s hydrological cycle recycles; it does not replenish. Every litre we contaminate, every litre we pump out of an aquifer faster than rain can refill it – that litre is removed from the accessible pool, and for all practical purposes, gone forever. What happens, then, when eight billion people, soon to be ten, start treating a finite teaspoon like an infinite resource? What happens when factories, farms and cities that depend on that teaspoon keep multiplying, while the teaspoon itself never grows? Thirsty atmosphere Climate change is not just warming the planet. It is rewiring the hydrological plumbing. There is a basic law of physics called the Clausius-Clapeyron relation. It states that for every degree Celsius the atmosphere warms, it can hold about 7% more water vapour. It means the sky behaves like a sponge that is getting bigger and thirstier. A warmer atmosphere pulls more moisture out of soil, out of plants, out of rivers and reservoirs. And when it finally releases that moisture, it does so in concentrated, violent bursts. This is why we are seeing a phenomenon that baffles people until they understand the physics behind droughts and floods intensifying at the same time, bizarrely often in the exact same places. Wet regions get wetter; dry regions get drier; both get more extreme. The sky is like a sponge that is getting bigger and thirstier. — VAN MAILIAN/Pexels In 2022, one-third of Pakistan spent months underwater after monsoon rains that, in some provinces, ran 500% above average. The floods displaced 33 million people. A 100km-wide lake formed in Sindh province and refused to drain for months. The same summer, Europe was living through its worst drought in five centuries. The Rhine, the continent’s economic artery, dropped so low that grain barges ran aground. The Loire could be crossed on foot. The Yangtze, in China, shrank so dramatically that a six-hundred-year-old Buddhist island temple re-emerged from the riverbed. It became a tourist attraction, but in reality, it is a silent alarm bell. The American Southwest is living through the most severe megadrought in 1,200 years. Lake Mead, the largest reservoir in the United States, hit its lowest level since it was filled in the 1930s. Forty million people depend on the Colorado River system, and the system is running dry. In 2023, for the first time, the federal government imposed mandatory water cuts across three states, a political reckoning that had been deferred for decades. The Horn of Africa has now suffered five consecutive failed rainy seasons. It is the longest drought in 40 years. Thirty six million people face acute food insecurity. Herders have lost their livestock. Farmers have abandoned their fields. Children are being treated for severe acute malnutrition in numbers that humanitarian agencies struggle to count. This is not a future projection. This is today. Cities built for the wrong climate In 2018, the city of Cape Town, with 4.5 million people and a modern functioning economy, came within days of turning off its municipal water supply entirely. “Day Zero,” they called it. The plan was grim and simple: residents would queue at 200 collection points for a daily ration of 25 litres per person, guarded by the army. The columnist says that if our entire planet’s water were a hundred-litre bathtub, the drinkable, accessible fraction would be about one teaspoon. — MONIKA BORYS/Unsplash Cape Town ultimately dodged Day Zero, barely, because after desperate conservation measures and, frankly, luck, the rains returned. But the experience exposed something that urban planners around the world are now grappling with: our cities were designed for a climate that no longer exists. São Paulo nearly ran dry in 2015. Chennai’s taps went empty in 2019 and 11 million people relied on water tankers for months. Mexico City, built on a drained lakebed five centuries ago, now pumps groundwater at twice the rate it recharges. Parts of the city are now sinking by up to 50cm a year. Roughly 30% of its water is lost through leaky pipes before it reaches a single tap. And then there is the opposite problem. When extreme rain hits a modern city, all that asphalt and concrete means that there is nowhere for the water to seep away. Cities are heat islands as well as impermeable basins: their dark surfaces absorb solar radiation, warming the air above them, which in turn pulls more moisture from the surrounding landscape and concentrates it overhead. The result is flash flooding that overwhelms drainage systems designed for milder rains. In July 2021, the Chinese city of Zhengzhou received a year’s worth of rain in three days, including 201.9mm in a single hour. The subway flooded within minutes. Fourteen people drowned in one tunnel. The storm sewers, intake pipes, runoff tunnels all failed: none of it had been built for this. Across the developed world, heavy rains increasingly force untreated sewage straight into rivers and lakes through something called “combined sewer overflows”, an intentional design feature supposed to activate only rarely. In the USA alone, an estimated 3.5 billion cubic metres of raw sewage and stormwater are discharged this way every year. That is more than a thousand Olympic swimming pools a day, every day. Can’t support crops Agriculture consumes roughly 70% of all the freshwater humanity uses. In developing countries, the figure can exceed 90%. And much of that water comes from underground sources. The Ogallala Aquifer, beneath America’s High Plains, is one of the largest bodies of freshwater on Earth. It waters roughly a quarter of all American crops. It is also, in many areas, being drained 50 to 100 times faster than rain can replenish it. Some wells that once struck water at 30m now go dry at 150m. The farmers simply drill deeper, chasing a resource receding beneath them. Agriculture consumes roughly 70% of all the freshwater humanity uses. — DAN MEYERS/Unsplash The same story plays out across the North China Plain, where the water table drops 1m to 3m every year. Across northwestern India, NASA’s satellites measured 109 cubic km of groundwater loss between 2002 and 2008. This is a volume twice the size of Lake Geneva, gone in six years. Across California’s Central Valley, the ground itself is sinking due to the aquifers beneath it being emptied like a deflating balloon. And then there is salinisation: the slow poisoning of farmland by salt. When farmers irrigate with groundwater, water evaporates but the salts do not. Over years and decades, salt accumulates until the soil can no longer support crops. Roughly 20% of the world’s irrigated land is now affected, and about 1.5 million more hectares are rendered useless each year. And when excess heat comes, such as when temperatures broke 45°C across the wheat belt in India in 2022 for weeks, many crops simply stop functioning. Wheat, rice, maize, and soybeans, which together provide three-quarters of human calories, have thermal limits. For each day above 30°C for wheat, yields drop by 1% to 5%. India’s wheat harvest fell by an estimated 15% that year and exports were banned. The next part deals with what we are putting into water, which renders water unusable. The views expressed here are entirely the author’s own.