Lake Texcoco
Lake Texcoco (“Lago de Texcoco”) was a natural lake within the “Anahuac” or Valley of Mexico. The lake was surrounded by marshes and forests, providing a habitat for various species of plants and animals in the area.
The lake was also an important source of fresh water for the valley’s inhabitants.
Lake Texcoco was the largest lake in Mesoamerica, covering an area of approximately 5,400 sq km. It was part of the interconnected system of lakes, which included Lake Xochimilco, Lake Chalco, and Lake Zumpango.
These lakes formed a vast inland water system that sustained the region.
Due to its size and strategic location, the Lake played a central role in the development of the Aztec Empire, providing water for agriculture and transport needs and also serving as a natural protective barrier for Tenochtitlan.
The lake was a source of fresh water and also provided water for irrigation, and fish for food, and served as a transportation route. The Aztecs built chinampas in the lake, which were artificial islands used for agriculture.
After the Spanish conquest of the Aztec Empire, efforts to control flooding by the Spanish led to most of the lake being drained. Extensive drainage projects initiated in the 17th century gradually reduced the size of the lake.
This alteration had profound ecological consequences for the region. Today, most of the lake’s former basin is almost entirely occupied by urban development in Mexico City. Only the remains of the original lake remain.
History & Timeline
Between the Pleistocene Era and the last Ice Age, Lake Texcoco occupied the entire Valley of Mexico. The lake reached its maximum extent 11,000 years ago, with an area of about 5,668 sq km and a depth of more than 152 m.
When the water level in the lake dropped, several paleolakes formed, which from time to time connected. To the north of San Miguel Tocuilla, there is an extensive paleontological field with several Pleistocene fauna.
The lake was fed primarily by snowmelt and rain runoff. Between 11,000 and 6,000 years ago the climate naturally warmed and snowfall became less common in central Mexico. This caused the lake’s water levels to drop.
Agriculture around the lake began about 7,000 years ago when people followed the patterns of the lake’s periodic flooding. Several villages appeared on the northeastern shore of Lake Texcoco between 1700 and 1250 BCE.
By 1250 BCE, hallmarks of the Tlatilco culture can be seen around the lake.
By roughly 800 BCE, Cuicuilco had eclipsed the Tlatilco cultural centers and became the major power in the Valley of Mexico during the approximately next 200 years when the famous conical pyramid of Cuicuilco was built.
The Xitle volcano destroyed Cuicuilco around 30 CE.
This eruption that destroyed Cuicuilco may have given rise to Teotihuacan. After the fall of Teotihuacan, 600–800 BCE, other city-states appeared around the lake, mainly under the influence of the Toltecs and Chichimecs.
Neither prevailed, and they coexisted more or less peacefully for several centuries. This time was described as the Golden Age in the Aztec chronicles. By 1300, the Tepanecs from Azcapotzalco began to dominate the area.
Tenochtitlan
Lake Texcoco is best known as the site where the Aztecs built the city of Tenochtitlan. Legend has it that the Mexica tribes wandered for 100 years before they came to the dense forests of what is now the Valley of Mexico.
Tenochtitlan was founded on an islet in the western part of the lake in the year 1325.
Around Tenochtitlan, the Aztecs created a large artificial island using a system similar to the creation of chinampas (floating gardens). The Aztecs built a system of dams to separate the lake’s salty waters from sewage rainwater.
This system of dams also permitted to Aztecs to control the level of Lake Texcoco. Tenochtitlan, nestled on the island within the lake, also had an inner system of channels that helped to control the water in the lake.
The Aztec ruler Ahuizotl attempted to build an aqueduct that would bring water from the mainland to the lakes surrounding the city of Tenochtitlan. The aqueduct failed and the city suffered severe flooding in 1502.
During Cortez’s siege of Tenochtitlan in 1521, the dams were destroyed and never rebuilt, so flooding became a major problem for Mexico City, which was built above the ruins of the former Aztec capital – Tenochtitlan.
Geography & Environment
The Valley of Mexico is a basin with an average elevation of 2236 m above mean sea level. This high altitude contributes to the region’s unique climatic and environmental characteristics. The valley is surrounded by mountains.
Previously the lake extended over much of the southern half of the basin, where it was the largest of an interconnected chain of five large and several smaller lakes (Texcoco, Lakes Xaltocan, Zumpango, Chalco, and Xochimilco).
During periods of high water levels – usually after the rainy season from May to October – all lakes often combine into one body of water at an average altitude of 2242 meters above mean sea level.
During the drier winter months, the lake system tended to split into separate bodies of water. This flow was mitigated by the construction of levees and dams during the Late Postclassic period of Mesoamerican chronology.
Lake Texcoco was located at the lowest altitude of the lakes in the Valley of Mexico. The lake acted as a natural sink for the basin, drawing water from the surrounding area as the culmination of the valley’s drainage system.
As Lake Texcoco was situated at the lowest point in the Valley of Mexico, it naturally collected water from the surrounding area. This meant that water from the higher lakes in the mountains flowed downhill towards Lake Texcoco.
Previously, rainwater flowed into the lakes, which contributed to their size and interconnectedness. Today, with the disappearance of Lake Texcoco and the drying of other lakes, the hydrology of the valley changed dramatically.
Without these natural reservoirs, rainwater has difficulty finding its way out, leading to problems in managing water flow and increasing evaporation rates. As a result, much of the rainwater that flows into the valley evaporates.
About 72-79% of the rainwater that falls into the valley evaporates.
Today, the term “Lake Texcoco” refers only to a big area surrounded by salt marshes 4 km east of Mexico City, which covers the ancient lake bed. Also, there are small remnants of the lakes of Xochimilco, Chalco, and Zumpango.
Artificial drainage
Mexico City suffered from periodic floods.
In 1604, the lake flooded the city, and in 1607 there was another, even more severe flood. A drainage was built to control the lake’s water levels, but in 1629 another flood kept most of Mexico City flooded for a long time.
The flood of 1629 was so severe that at that time it was even seriously debated whether to relocate the capital of New Spain or not, but the Spanish authorities decided to maintain the current location of Mexico City.
Flooding could not be completely controlled until the 20th century.
In 1967, the construction of the Deep Drainage System (network of several hundred km of tunnels) was done, at a depth between 30 and 250 m. The central tunnel has a diameter of 6.5 m and carries rainwater out of the basin.
The environmental consequences of drainage were enormous.
Some parts of the valley have become semi-arid, and Mexico City suffers from water shortages. Due to excessive rainfall that is depleting the aquifer beneath the city, Mexico City has fallen 10 meters over the past century.
Because soft lake sediments underlie much of Mexico City, the city has proven vulnerable to soil liquefaction during earthquakes, especially the 1985 quake that collapsed hundreds of buildings and killed thousands of people.
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