On the black market, a large bucket of water sells for as much as $100, and the vehicles delivering the water have more police personnel than the cash trucks. This happened in Mexico City, one of the largest cities in the world.
Mexico City is the capital of Mexico and one of the few cities in the world with a population of more than 20 million. However, the latest forecast data shows that Mexico City will usher in the so-called “Day Zero” as soon as June 26 this year.
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“Day zero” refers to the complete depletion of the city's water supply system. It cannot provide residents with a drop of drinking water, and factories cannot operate. As a result, the city will fall into a crisis of collapse.
Mexico is considered by some organizations to be one of the 11 cities in the world most likely to attract “Day Zero”, and their fresh water resources have been severely scarce.
But how did such a big city get to where it is today? Will there be similar problems in other big cities?
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Why is Mexico City experiencing severe water shortage?
The reason why Mexico suffers from serious water shortages can be summed up as the over-expansion of cities, which has caused the city's water supply to far exceed demand. The natural storage system of water resources has also been destroyed due to over-development, and climate change has made the problem becomes more severe.
Mexico City has been a prosperous city in Central America since ancient times. The ancient Aztecs established the city here. However, the ancient Mexico City was built on an island in Lake Texcoco and was surrounded by freshwater lakes. The Aztecs People only built some artificial canals and did not destroy the original lakes.
After the Spanish occupied the city in the 16th century, they drained the original lakes, filled in the canals, and rebuilt Mexico City because they felt that these lakes were obstacles to the expansion of the city.
Mexico City became more and more prosperous under the operation of the Spanish and became one of the largest cities in the world. However, prosperity naturally brought over-exploitation of resources. Mexico City's water resources problems have been on display since the last century.
Due to the disappearance of freshwater lakes, Mexico City has lost its surface water source. Most of its water comes from underground aquifers – about 60%. The extraction of aquifers has led to another problem – urban subsidence.
Urban subsidence may mean that for some coastal cities it will be intruded by sea water, but this will not be the case for Mexico City, which is more than 2,000 meters above sea level.The impact of subsidence on Mexico City is that it loses its underground water storage capacity.
With the extraction of groundwater, the already densely packed underground mineral soil will be further compacted. The end result is naturally that the water brought by heavy rains will be more difficult to penetrate into the aquifer for storage.
This is an irreversible process and a vicious cycle, because water cannot replenish the aquifer well, which will cause Mexico to sink more and more, making it increasingly difficult to store water.
Because of this, even though Mexico City banned all groundwater extraction activities in the city center in the 1950s, the city is still sinking at a rate of 0.5 meters per year.
Now, Mexico City's main water use has shifted to the periphery – obtaining water from distant peripheries through water conservancy projects. In 2021, a study claimed that there is no hope of a significant recovery in Mexico City's storage capacity, so drawing water from the surrounding areas will only become more frantic and the cost will become increasingly expensive.
Climate change makes things worse
In fact, water shortage in Mexico City is nothing new. For a long time, 20% of the people in the city have only had the opportunity to use the tap for a small part of the day.
But this year has been particularly severe, and water conservancy experts believe it is related to climate change, which changes rainfall and temperature patterns.
The total precipitation in 2023 is 25% less than the average of the past 30 years, and it has also suffered from severe drought so far in 2024. This situation is probably due to climate change and changes in the rain belt.
Moreover, due to this year's El Niño phenomenon, temperatures have increased throughout Latin America, and severe heat waves have made Mexico City, which is already short of water, even more water-scarce.
The rainy season in Mexico City does not start until May or June, but currently it seems that the water supply system there may not be able to wait until the rainy season. In addition, even if there is no “zero day” this year, the future is not optimistic.
Most cities face similar problems
In fact, Mexico City is just an extreme example. Currently, almost all cities in the world are facing water supply problems, especially in large cities. The situation is not optimistic.
In 2014, a survey of the world's 500 largest cities found that a quarter of the cities were suffering from water shortages.
Urban expansion often destroys geological structures, and swampy areas that originally had water storage capacity are often filled in as in Mexico City – areas that usually flood when heavy rains in the city are often swamps.
Simply put, as long as we expand, there will be problems with the city's water storage capacity, which is not good news for areas where rainfall itself is not very abundant.
Of course, many cities do not rely heavily on underground water storage. Many large cities mainly rely on surface water-this water includes rivers, lakes, and snowmelt.
However, cities that rely on surface water also face water problems. For example, Tokyo, where 70% of water comes from the surface, is also one of the 11 cities in the world most likely to run out of drinking water.
The reason is simple. Cities that rely on surface water usually face the problem of uneven rainfall. Tokyo’s annual rainfall is basically concentrated in four months. Tokyo has built at least 750 rainwater collection and utilization systems for this purpose.
The problem of uneven rainfall will be exacerbated by climate change, with changing rain patterns making cities either drier or more waterlogged, rarely for the better.Because our cities are often built in very livable places, places that have always had good weather.
at last
I once read a statement that drinking water will be more valuable than oil in a few years. This statement may be a bit alarmist, but it is inevitable that available freshwater resources will become increasingly scarce.
Although about 70% of the earth's surface is covered with water, only about 3% is fresh water, and 68% of it is in glaciers. The amount of fresh water that can actually be utilized is less than imagined. Coupled with uncontrolled development and pollution, it can It is said that fresh water resources are indeed in danger.
According to projections recognized by the United Nations, due to the combined effects of climate change, human activities and population growth, global freshwater demand will exceed supply by 40% by 2030, and it is estimated that more people will face water problems by then.