Chinampas, the floating gardens of a sinking city
Xochimilco is a southern district of Mexico City famous for its canals. Both locals and tourists come to Xochimilco to ride colorful boats and enjoy an atmosphere far removed from the rest of the bustling metropolis.
Mexico City was built on the ruins of Tenochtitlan, the capital of the Aztec Empire. The city of Tenochtitlan was built in 1325 on an island off the western shore of Lake Texcoco in the Valley of Mexico (Valley Anahuac).
According to Aztec mythology, Huitzilopochtli, the god of war, sent them to go to a new place beyond their former lands and build a city on the spot where they saw an eagle sitting on a cactus and devouring a snake.
The Aztecs built an extensive network of canals and artificial islands – chinampas. These so-called “floating islands” were also used for agricultural purposes, providing high yields and feeding a growing population.
Over time, Mexico City grew and expanded, the canal systems were filled to build roads, and the foundation of the lake bed was forgotten. This led to the overuse of groundwater, soil collapse, and flooding of the city.
Canals of Xochimilco
The canals of Xochimilco are not only a popular destination for boat trips. These canals and the man-made islands that surround them – chinampas – are silent witnesses to Mexico City’s distant pre-Columbian past.
The technology for making chinampas was developed in Mesoamerica before the Aztecs, but it was the Aztecs who used it on a huge scale. Despite the common term “floating gardens”, chinampas do not actually float.
Famous chinampas are built by creating a fence using wooden stakes on the lake. This enclosure is then filled with alternating layers of mud and decaying vegetation until solid ground is formed above the water level.
An artificial island is thus formed and trees are planted along the edges since the roots of the trees help prevent erosion.
Chinampas of Xochimilco
Chinampas are artificial islands held together by wooden stakes and tree roots. The mixture of dirt and vegetation makes the soil very fertile and is one of the reasons why the chinampas are extremely productive.
The canal water also contains fish, which not only provides more food but also adds nitrogen-rich manure, which in turn fertilizes the plants. The fish in the canals from which chinampa was prepared had benefits.
Fish served as an additional source of food, and played a crucial role in fertilizing crops. Their nitrogen-rich excrement acted as a natural fertilizer for plants grown, increasing the agricultural productivity of chinampas.
This farming system was an ingenious way to maximize agricultural efficiency.
Generally, no irrigation is required as the plants absorb water directly from the channels, and overuse of water is prevented as the plants only absorb the water they need. The system is also drought and flood-resistant.
Chinampas that are used today function a little differently. Greenhouses are usually used. Today, instead of producing food, Xochimilco’s chinampas are mainly used to grow the flowers for which Xochimilco is famous.
The also Aztecs grew flowers in the chinampas of Xochimilco. Xichimilco means “garden of flowers” in the Nahuatl language. However, since chinampas are very productive, they are also good for small-scale farming.
Chinampas are very productive, and although today they are mainly used for growing flowers, they also have the potential for efficient food production, which could help reduce poverty and improve food security.
The network of canals and chinampas in Xochimilco today is just a glimpse of what it used to be. Urban sprawl, climate change, pesticides, pollution, and neglect are all contributing to the slow destruction of the chinampas.
Today, these systems of canals and chinampas face many threats, and one of them is the spread of invasive water hyacinths, which can be seen congregating near the shorelines, posing challenges to the local ecosystem.
From a floating city to a sinking city
The Aztecs were great engineers. The canals and chinampas of Xochimilco are only a small part of the original network of canals and artificial islands that spanned the city of Tenochtitlan and its surrounding areas.
These canal systems were connected to a system of dams, levees, and aqueducts that together helped provide water to the inhabitants of Tenochtitlan while simultaneously controlling the water levels in the canals.
The Aztecs also used terraces and irrigation canals to produce enough food.
When the Spanish arrived, Tenochtitlan had about 200,000 inhabitants. But the Aztecs could not even dream that several centuries later a metropolis with a 20 million population would lie on the same foundation.
The Spaniards drained canals, and the land began to appear solid, but the former lake bed could never be truly solid. When the system of aqueducts and canals collapsed, Mexico City began to pump out groundwater.
Groundwater is being drawn from aquifers beneath Mexico City faster than it is naturally replenished, causing the land to subsidence. This process causes buildings to lean and crack as the ground beneath them settles.
Many buildings in Mexico City are leaning because the ground beneath them is eroding due to overuse of groundwater. In this context, the canals and chinampas of Xochimilco serve as silent reminders of the city’s past.
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