Megacities, Water Scarcity, Climate Change

Roughly twenty-one million people live in Greater Mexico City, but estimates show residents take 2.15 times of the water in aquifers than is recharged or recovered, making the city to be in danger of running out of water.

According to Wikipedia, about five million people see Johannesburg in South Africa as home, but officials say the failure to reduce people's water consumption could mean the reservoirs in the city dropping below ten percent capacity, meaning the city stands on the verge of running out of water.

Nearly 12 million people live in the southern Indian city of Greater Chennai, but the gap between their demand and supply of water could surge to almost 466 megaliters per day by 2031, implying the city could face the condition it encountered in 2019, when it almost ran out of water.

The situation in Mexico City, Johannesburg, and Chennai indicate the challenges megacities face in relations to water, but they're not the only megacities affected, as others such as Sao Paulo, Bangalore, Beijing, Cairo, Jakarta, Moscow, Istanbul, London, Tokyo, Miami, among others face the prospect of running out of water one day.

Along with the lack of recovery of its aquifers, severe drought from climate change took its toll in Greater Mexico City, allowing the aquifers to stand at around 39 percent of capacity, languishing at a historic low, a situation exacerbated by  temperatures as high as nearly 85 degrees Fahrenheit last week, a figure to hit 90 degrees Fahrenheit with a minimum cloud cover.

Aging infrastructures take their toll in the South African city of Johannesburg, because pipes older than 70 years break, releasing large quantities of water as leaks, implying that six million people rely on a system designed for fewer people.

Over the years, Chennai thrived on its reputation as one of the world's wettest cities, but when industrialization, urbanization, and extreme weather through climate change converged, water shortages became inevitable, especially as the city continues to add a quarter of a million people to its population every year.

Apart from drought, leaks from the water system, and high temperatures, megacities run out of water due to expanding populations, with  cities such as Bangalore growing faster than expected, its population slated to reach 20 million in 2031 from 13 million today, while cities such as Cairo suffer from the pollution of the River Nile, a situation compounded by the entirety of Egypt suffering from a deficit of up to seven billion cubic meters of water per year.

With megacities running out of water, officials need a greater quantity of energy to pump water, leading to an increase in greenhouse gas emissions, a dangerous situation, as the 50 largest cities together already emit 2,600 megatons of carbon dioxide per year.

With megacities facing the challenges of water, residents may resort to unsustainable practices like deforestation and land use changes to secure water sources, causing a reduction in carbon sinks, a dangerous situation, as people already cut down 10 million hectares of forest each year.

With megacities running out of water, urban heat islands proliferate, absorbing and retaining heat, leading to rising energy demands for cooling to mitigate the effects of higher temperatures, a dangerous situation, with a global increase of 0.19 degrees Celsius per decade from 1979 to 2022  accelerating to an increase of  0.25 degrees Celsus per decade from 1986 to 2015.

Needless to say, climate change will worsen when megacities run out of water, because water shortages come with higher temperatures, the recourse to unsustainable practices like deforestation and land use changes, as well as the drastic rise in greenhouse gas emissions.

Slowed population growth, climate change mitigation, and water use efficiency could solve water scarcity in 68 large cities including New York, São Paulo, Mumbai, Dhaka, and Jakarta, according to a study.

Megacities could also avoid or discourage the wasteful usage of water, because not only will it bring availability of the resource, it will also contribute to the solution of an immense global problem, the loss of 30 percent of the global water supply through leaks each year, a figure equating to around 2.1 trillion gallons of water wasted.

When megacities run out of water, the effects of the worst aspects of climate change manifest, but through slowed population growths, water-use efficiency, and the avoidance of wasteful water uses, people can be spared of a lot of trouble.

What to Eat

Vegan food from Mexico, Credit, Epicure and Culture