Texcoco Lake
Coordinates: 19 ° 25 ′ 10 ″ N , 99 ° 8 ′ 0 ″ W.
The Texcoco lake is a lake in the south of the valley of Mexico , which has now almost completely dried up . As a final lake , it had no drains; its water was also very salty because of the strong evaporation. Originally, he took a large part of the Anahuac Valley and trained together with the Xaltocan Lake , the Zumpango Lake , the Chalco Lake and the Xochimilco Lake a larger lake system. The lake system was 2270 to 2750 meters above sea level .
Prehistory and early history
In the Pleistocene , this lake system extended over a much larger area. There were several paleo lakes that were in communication from time to time. In the north of the modern settlement of Tocuila there is a large paleofield , in which there are numerous indications of a rich Pleistocene fauna .
An agricultural use of the lake shore is for the first time around 7000 BC. BC (Lorenzo, 1981; Niederberger, 1979). Obviously the people followed the periodic floods in their settlement patterns .
Several pre-Columbian cultures developed around the entire lake . On the northeast bank were between 1700 and 1100 BC. Several villages characterized by characteristic ceramic sculptures ("smiling faces"). On the southern bank was also around 1200 BC. Founded Cuicuilco .
Formative phase
Due to the strong volcanic activity of this region, after an eruption of the volcano Xitle Cuicuilco destroyed it, settlement shifted to the northern shore of the lake. The great city of Teotihuacán was also founded here.
After the decline of Teotihuacán, several city-states (including Xoloc , Azcapotzalco , Tlacopan , Coyohuacan , Culhuacán , Chimalpa and Chimalhuacán ) were re-established around the lake - mainly under the influence of the Toltecs and Chichimecs . However, none of these state structures succeeded in gaining supremacy over the other, so people lived more or less peacefully together. This time is also described in the Aztec chronicles as the " Golden Age ".
Around 1300 the Tepanecs began to expand their domain from their capital, Azcapotzalco .
Aztec rule
In 1325, the city of Tenochtitlan was finally founded on a small island in the western part of the lake . With the help of the so-called chinampas , the Aztecs created large artificial islands. In order to guarantee the drinking water supply, they built a dam system, which separated the salt water of the lake from the rainwater of the tributaries and at the same time allowed to regulate the water level of the lake. There was also a canal system in the center of Tenochtitlán itself.
The drainage problem in colonial times
In the course of the Spanish conquest of Mexico and the siege of Tenochtitlán by Hernán Cortés in 1521, the dams were destroyed for tactical reasons. The houses of the city were torn down to take cover from the Aztecs. The rubble was simply poured into the canals after the fighting.
As early as 1540, however, there were repeated floods as a result of heavy rainfall, so that the conquistadors themselves made efforts to repair the dam system. However, these efforts were made more difficult by the fact that the forest stock was greatly reduced as a result of the construction of the ships that were so vital to the war effort and as a result of overgrazing by the pack animals introduced by the Spaniards , which in turn favored soil erosion and increased the problem of flooding.
For the city of Mexico , built on the ruins of Tenochtitlán , floods remained a serious problem throughout the colonial period . The great flood from 1629 to 1633, for example, in which parts of Mexico City were under water for up to five years, cost the lives of tens of thousands of people and several thousand left the city. At that time, the Spanish authorities were even considering building Mexico City from scratch elsewhere.
As early as the 16th century there were plans for large-scale drainage projects. After an initial failure, these were so successful towards the end of the 18th century that Lake Texcoco had disintegrated into five small basins around 1800 and Mexico City was outside the lake. As early as 1807, Alexander von Humboldt felt compelled to point out the deforestation of the region and the erosion of the soil as the impending dangers of rigorous drainage.
The consequences of draining
In the 19th and 20th centuries, in the course of industrialization, the drainage of the lake was pushed further, also in order to gain more settlement area for the rapidly expanding modern metropolis.
Due to the increasing population density, however, the problem of irrigation and drainage became even more acute. Due to the lack of drinking water, groundwater had to be pumped up from deep wells at an early stage , which in turn contributes to the considerable subsidence (sometimes up to eight meters). As a result, the stability of the structures (including the irrigation and drainage channels) in the region, which is already extremely prone to earthquakes, is further impaired.
The subsidence also makes it difficult to investigate archaeological remains of the Aztec Tenochtitlan, as some of them are too deep or an excavation would risk their destruction.
In addition, the drainage of Lake Texcoco has serious ecological consequences. Parts of the Anahuac Valley were practically turned into deserts - one of the reasons for the frequent dust storms ( Tolvaneras ) that hit this region again and again. Some endemic species that settled or developed around the lake are either extinct or threatened with extinction (compare for example axolotl ).
In 1971 the environmental project "Project Texcoco" was launched. As part of this project, artificial lagoons are created on the former lake bed and supplied with treated water in order to preserve at least remnants of the fauna and flora of the lake.
Most of the original area of the lake is now occupied by Mexico City. Only a small area of the original lake is still preserved and is located about four kilometers east of Mexico City. Even the Xochimilco Lake , the Chalco Lake and Zumpango Lake exist only in remains.