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Lake Texcoco
From Wikipedia, the free encyclopedia
Lake Texcoco was a lake in Mexico. It formerly occupied a great extension of the Valley of Mexico, forming part of system of five lakes, which included Lakes Xaltocan, Zumpango, Chalco and Xochimilco, all between 2,270 and 2,750 meters above sea level. Because it was formed within a closed basin, with no outlet and subject to evaporation, Lake Texcoco was an endorheic lake.
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In the Pleistocene era, the lake occupied an even greater area. There were several paleo-lakes that would connect with each other from time to time. At the north in the modern population of Tocuila there is a great paleontological field, with a lot of pleistocenic fauna. The remains of seven mammoths dated 11,188 years old (BP) were found, suggesting human presence.
Agriculture around the lake began about 7,000 years BP (Lorenzo, 1981; Niederberger, 1979) with humans following the patterns of periodic inundations of the lake.
On the northeast side of the lake, between 1700 and 1250 BCE, several villages appear. By 1250 BCE, the identifying signs of the Tlatilco culture, including more complex settlements and a stratified social structure, are seen around the lake. By roughly 800 BCE, Cuicuilco had eclipsed the Tlatilco cultural centers and was the major power in the Valley of Mexico during the next 200 years, when its famous conical pyramid was built. The Xitle volcano destroyed Cuicuilco around 30 CE, a destruction that may have given rise to Teotihuacan.
After the fall of Teotihuacan, 600 - 800 CE, several other city states appeared around the lake, including Xoloc, Azcapotzalco, Tlacopan, Coyohuacan, Culhuacán, Chimalpa and Chimalhuacán -- mainly from Toltec and Chichimec influence. None of these predominated and they coexisted more or less in peace for several centuries. This time was described as a Golden age in Aztec chronicles. By the year 1300, however, the Tepanec from Azcapotzalco were beginning to dominate the area.
According to a traditional story, the Mexica wandered in the deserts of modern Mexico for 100 years before they came to the thick forests of the place we now call the Valley of Mexico.
Tenochtitlan was founded on an islet in the western part of the lake in the year 1325. Around it, the Aztecs created a large artificial island using a system similar to the creation of chinampas. To overcome the problems of drinking water, the Aztecs built a system of dams to separate the salty waters of the lake from the rain water of the effluents. It also permitted them to control the level of the lake. The city also had an inner systems of channels that helped to control the water.
During Cortés's siege of Tenochtitlan, the dams were destroyed, and never rebuilt, so flooding became a big problem for the new Mexico City built over Tenochtitlan. In colonial times, Mexico City suffered from periodic floods; in 1604 the lake flooded the city with an even more severe flood following in 1607. Under the direction of Heinrich Martin a drain was built to control the level of the lake, but in 1629 another flood kept most of the city covered for five years. In that time it was debated whether to relocate the city, but the Spanish authorities decided to keep the current location.
Eventually the lake was drained, via channels and a tunnel to the Pánuco River, but even that could not stop floods, since by then most of the city was under the phreatic level. The flooding could not be completely controlled until the twentieth century. In 1967 construction began of the Drenaje Profundo, a network of several hundred kilometers of tunnels, at a depth between 30 to 250 meters. The central tunnel has a diameter of 6.5 meters and carries rain water out of the valley.
The ecological consequences of the draining were enormous. Parts of the valleys were turned semi-arid, and even today Mexico City suffers for lack of water. Current pumping of water from underground is one of the reasons Mexico City is sinking at a rate of a few centimeters every year.
The term "Texcoco Lake" now refers only to a small area surrounded by salt marshes 2 1/2 mi (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.
Several species indigenous to the lake are now extinct or in danger.
The modern Texcoco Lake has a high concentration of salts, and its waters are evaporated for their processing. A Mexican company, "Sosa Texcoco S.A" has a 800-hectare solar evaporator known as "El caracol".
- Mammoth bone technology at Tocuila in the Basin of Mexico, (Morett et al. 1998a)