Lake Texcoco
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Lake Texcoco is a lake in Mexico. The lake was formed on a closed basin, with no drains, so it was salty. It occupied a great extension of the Anahuac valley, forming part of system of five lakes, between 2,270 and 2,750 meters above sea level, in the northern part of the Mexican highlands.
Tenochtitlán was founded on an islet in the western part of the lake in the year 1325. 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, with 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 Tenochtitlán, the dams were destroyed, and never rebuilt, so inundations became a big problem for the new Mexico City built over Tenochtitlán. In colonial times, Mexico City suffered from periodic inundations; in 1604 the lake overran the city and in 1607 there was an even more severe inundation. Under the direction of Enrico Martínez (Spanish version of Heinrich Martin), a drain was built to control the level of the lake, but in 1629 another inundation kept most of the city covered for five years. In that time it was debated whether to relocate the city, but the Spanish authorities decide 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 inundations, since by then most of the city was under the phreatic level. The inundations could not be completely controlled until the twentieth century.
The ecologial consequences of the draining were enormous. Parts of the valleys were turned semi-desertic, and even today the 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 lake now occupies only a small area surrounded by salt marshes 2 1/2 mi (4 km) east of Mexico City.