Valley of Mexico

The Valley of Mexico (Spanish: Valle de México; Nahuatl languages: Tepētzallāntli Mēxihco) is a highlands plateau in central Mexico roughly coterminous with present-day Mexico City and the eastern half of the State of Mexico. Surrounded by mountains and volcanoes, the Valley of Mexico was a centre for several pre-Columbian civilizations, including Teotihuacan, the Toltec, and the Aztec. The ancient Aztec term Anahuac (Land Between the Waters) and the phrase Basin of Mexico are both used at times to refer to the Valley of Mexico. The Basin of Mexico became a well known site that epitomized the scene of early Classic Mesoamerican cultural development as well.

The Valley of Mexico is located in the Trans-Mexican Volcanic Belt.[1][2] The valley contains most of the Mexico City Metropolitan Area, as well as parts of the State of Mexico, Hidalgo, Tlaxcala and Puebla. The Valley of Mexico can be subdivided into four basins, but the largest and most-studied is the area which contains Mexico City. This section of the valley in particular is colloquially referred to as the "Valley of Mexico".[3] The valley has a minimum elevation of 2,200 meters (7,200 ft) above sea level and is surrounded by mountains and volcanoes that reach elevations of over 5,000 meters (16,000 ft).[4] It is an enclosed valley with no natural outlet for water to flow and a gap to the north where there is a high mesa but no high mountain peaks. Within this vulnerable watershed all the native fishes were extinct by the end of the 20th century.[5] Hydrologically, the valley has three features. The first feature is the lakebeds of five now-extinct lakes, which are located in the southernmost and largest of the four sub-basins. The other two features are piedmont, and the mountainsides that collect the precipitation that eventually flows to the lake area. These last two are found in all four of the sub-basins of the valley.[1][3] Today, the Valley drains through a series of artificial canals to the Tula River, and eventually the Pánuco River and the Gulf of Mexico. Seismic activity is frequent here, and the valley is considered an earthquake prone zone.[6]

The valley has been inhabited for at least 12,000 years, attracting humans with its mild climate (average temperatures between 12 and 15 °C, or 54 and 59 °F), abundant game and ability to support large-scale agriculture.[7][8] Civilizations that have arisen in this area include the Teotihuacan (800 BC to 800 AD) the Toltec Empire (10th to 13th century) and the Aztec Empire (1325 to 1521).[7] When the Spaniards arrived in the Valley of Mexico, it had one of the highest population concentrations in the world with about one million people.[2] After the Conquest, the Spaniards rebuilt the largest and most dominant city here, Tenochtitlan, renaming it Mexico City. The valley used to contain five lakes called Lake Zumpango, Lake Xaltocan, Lake Xochimilco, Lake Chalco, and the largest, Texcoco covering about 1,500 square kilometers (580 sq mi) of the valley floor,[2] but as the Spaniards expanded Mexico City, they began to drain the lakes' waters to control flooding.[7] Although violence and disease significantly lowered the population of the valley after the Conquest, by 1900 it was again over one million people.[9] The 20th and 21st centuries have seen an explosion of population in the valley along with the growth of industry. Since 1900, the population has doubled every fifteen years. Today, around 21 million people live in the Mexico City Metropolitan Area which extends throughout almost all of the valley into the states of Mexico and Hidalgo.[2]

The growth of a major urban, industrial centre in an enclosed basin has created significant air and water quality issues for the valley. Wind patterns and thermal inversions trap contaminants in the valley. Over-extraction of ground water has caused new flooding problems for the city as it sinks below the historic lake floor. This causes stress on the valley's drainage system, requiring new tunnels and canals to be built.[6][10]

Valle de México José Maria Velazco 3
A 19th-century painting of the Valley of Mexico by José María Velasco.
Lake Texcoco c 1519
The lake system within the Valley of Mexico at the time of the Spanish Conquest in around 1519.
Basin of Mexico 1519 map-en
The Valley of Mexico basin, ca. 1519

History of human habitation

First human habitation

The Valley of Mexico attracted early humans because the region was rich in biodiversity and had the capacity of growing substantial crops.[7] Generally speaking, humans in Mesoamerica, including central Mexico, began to leave a hunter-gatherer existence in favor of agriculture sometime between the end of the Pleistocene epoch and the beginning of the Holocene.[8] The oldest known human settlement in the Valley of Mexico is located in Tlapacoya, located on what was the edge of Lake Chalco in the southeast corner of the valley in contemporary Mexico State. There is reliable archeological evidence to suggest that the site dates as far back as 12,000 BC. After 10,000 BC, the number of artifacts found increases significantly. There are also other early sites such as those in Tepexpan, Los Reyes Acozac, San Bartolo Atepehuacan, Chimalhuacán and Los Reyes La Paz but they remain undated. Human remains and artifacts such as obsidian blades have been found at the Tlapacoya site that have been dated as far back as 20,000 BC, when the valley was semi-arid and contained species like camels, bison and horses that could be hunted by man.[11] However, the precise dating of these artifacts has been disputed.[8]

Museo paleontologico de Tocuila-mandibula
A Columbian mammoth jaw excavated at Tocuila

Giant Columbian mammoths once populated the area, and the valley contains the most extensive mammoth kill sites in Mexico. Most of the sites are located on what were the shores of Lake Texcoco in the north of the Federal District and the adjacent municipalities of Mexico State such as in Santa Isabel Ixtapan, Los Reyes Acozac, Tepexpan and Tlanepantla.[12] Mammoth bones are still occasionally found in farmland here. They have been discovered in many parts of the Federal District itself, particularly during the construction of the city's Metro lines and in the neighborhoods of Del Valle in the center, Lindavista to the center-north and Coyoacán in the south of the city. The symbol for Line 4's Talisman station of the Mexico City Metro is a mammoth, due to the fact that so many bones were uncovered during its construction [13]. However, the richest site for mammoth remains in the valley is at the Paleontological Museum in Tocuila, a 45-hectare (110-acre) site located near the town of Texcoco in Mexico State.[12] Although there is some evidence around the old lakeshores that the first populations here survived by hunting, gathering and possibly by scavenging, but evidence from this time period is scarce.[8]

Pre-Teotihuacan

SEViewCuicuilcoDF
Modern-day Cuicuilco
Acróbata de Tlatilco
Ceramic art recovered from Tlatilco, circa 1300–800 BC

Tlatilco was a large pre-Columbian village and culture in the Valley of Mexico situated near the modern-day town of the same name in the Mexican Federal District. It was one of the first significant population centers to arise in the valley, flourishing on the western shore of Lake Texcoco during the Middle Pre-Classic period,[14] between 1200 BC and 200 BC.[15] It was originally classified as a necropolis when it was first excavated, but it was determined that the many burials there were under houses of which nothing remains. It was then classified as a major chiefdom center. The Tlatilcans were an agricultural people growing beans, amaranth, squash and chili peppers, reaching their peak from 1000 to 700 BC.[15]

The next-oldest confirmed civilization is in the far south of the valley and is called Cuicuilco.[16] This archaeological site is located where Avenida Insurgentes Sur crosses the Anillo Periférico in the Tlalpan borough of the city. The old settlement once extended far beyond the boundaries of the current site, but it is buried under lava from one of the volcanic eruptions that led to its demise, and much of the modern city is built over this lava. The settlement was located where an old river delta used to form in the valley with waters from Mount Zacatépetl located in what is now the Tlalpan Forest. Cuicuilco was believed to have reached city status by 1200 BC and began to decline around 100 BC - AD 150. However, even though the ceremonial pyramid was abandoned, the site remained a location to leave offerings up to AD 400, although lava from the nearby Xitle volcano completely covered it.[16]

Teotihuacan and the Toltecs

Around 2,000 years ago, the Valley of Mexico became one of the world's most densely populated areas and has remained so since.[2] After the decline of Cuicuilco, the population concentration shifted north, to the city of Teotihuacan and later to Tula, both outside the lake's region of the valley.[9] Teotihuacan became an organized village around 800 BC but it was around 200 BC that it began to reach its height. When it did, the city had approximately 125,000 inhabitants and covered 20 square kilometers (8 sq mi) of territory. It was dedicated primarily to the obsidian trade and at its peak was an important religious center and pilgrimage for the valley.[17] In the early 8th century, with the rise of the Toltec empire, Teotihuacan ceased to be a major urban centre and the population shifted to Tollan or Tula on the northern front of Valley of Mexico.[9]

Aztec Empire

After the end of the Toltec empire in the 13th century and the decline of the city of Tula, the population shifted once again, this time to the lakes region of the valley. With this migration came the concept of a city-state based on the Toltec model. By the end of the 13th century, some fifty small urban units, semi-autonomous and with their own religious centers, had sprung up around the lakeshores of the valley. These remained intact with a population of about 10,000 each under Aztec rule and survived into the colonial period. All of these city-states, including the largest and most powerful, Tenochtitlan, with more than 150,000 inhabitants, claimed descent from the Toltecs. None of these cities was completely autonomous or self-sufficient, resulting in a conflictive political situation, and a complex system of agriculture in the valley.[9] These city-states had similar governmental structures based on the need to control flooding and store water for irrigating crops. Many of the institutions created by these hydraulic societies, such as the building and maintenance of chinampas, aqueducts and dikes, were later co-opted by the Spanish during the colonial period.[18]

The largest and most dominant city at the time of the Spanish conquest was Tenochtitlan. It was founded by the Mexica (Aztecs) on a small island in the western part of Lake Texcoco in 1325, and was extended with the use of chinampas, human-made extensions of agricultural land into the southern lake system, to increase productive agricultural land, covering about 9,000 hectares (35 sq mi).[9] The inhabitants controlled the lake with a sophisticated system of dikes, canals and sluices. Much of the surrounding land in the valley was terraced and farmed as well, with a network of aqueducts channeling fresh water from springs in the mountainsides into the city itself.[2] Despite being the dominant power, the need to rely on resources from other parts of the valley led to the Aztec Triple Alliance between Tenochtitlan, Texcoco and Tlacopan at the beginning of the empire. However, by the time the Spanish arrived in 1519, Tenochtitlan had become the dominant power of the three, causing grievances that the Spaniards were able to exploit.[9] However, despite Tenochtitlan's power outside the valley, it never completely controlled all of the valley itself, with the altepetl of Tlaxcala the most prominent example.[9]

By 1520, the estimated population of the valley was over 1,000,000 people.[2]

Spanish colonial rule and the Mexico City metropolitan area

After the Spanish conquest of the Aztec empire in 1521, the Spanish rebuilt and renamed Tenochtitlan as Mexico City. They started with essentially the same size and layout as the Aztec city but as the centuries progressed, the city grew as the lakes shrank. Just after the conquest, disease and violence had decreased the population in the valley, especially of the native peoples, but after that, the population grew all through the colonial period and in the century after independence.[9]

By the early 20th century, the population of Mexico City alone had risen to over one million people. A population explosion began early in the 20th century, with the population of the city itself doubling approximately every 15 years since 1900, partly attributed to the fact that the federal government has favored development of the metropolitan area over other areas of the country.[2] This has spurred investment in infrastructure for the city, such as electricity, other power sources, water supply and drainage. These have attracted businesses which in turn have attracted more population. Since the 1950s, urbanization has spread out from beyond the bounds of the Federal District to the surrounding jurisdictions, especially to the north into the State of Mexico making for the Mexico City Metropolitan area, which fills most of the valley.[2] Today, this metropolitan area accounts for 45 per cent of the country's industrial activity, 38 percent of GNP, and 25 percent of the population.[2] Much of its industry is concentrated in the northern part of the Federal District and the adjoining cities in the state of Mexico.[6] While population growth has slowed and even declined in the city proper, the outer limits of the metropolitan area keep growing. Much of this growth has occurred on the mountainsides of the valley, in the form of illegal settlements in ecologically sensitive areas.[2] Overall urban settlement in the valley has expanded from about 90 km2 (35 sq mi) in 1940 to 1,160 km2 (450 sq mi) in 1990.[2] The metropolitan area has about 21 million residents and about 6 million cars.[19]

Air pollution

Mexico City is vulnerable to severe air pollution problems due to its altitude, its being surrounded by mountains and the winds patterns of the area.[6][10][20] The altitude, with its low oxygen levels, makes for poor combustion of fossil fuels leading to unsafe levels of nitrogen oxides, hydrocarbons, and carbon monoxide.[6] The valley is surrounded by mountain ranges with one small opening to the north. The surrounding mountains and climate patterns here make it difficult to clear out the smog produced.[10] The valley has internal wind patterns which circulate around the valley without a prevailing wind to push contaminants in a single direction.[6] The most significant climatic phenomena here is "thermal inversion," which is prevalent in the winter months when the cooler air of the valley is trapped by relatively warmer air above. Adding to this is that prevailing winds outside the valley move from north to south, in through the Valley's one opening, where incidentally most of the region's industry is located.[6] These factors diminish in the summer and the situation is helped by the arrival of the rainy season,[6] but the valley's southern latitude and the abundance of sunlight allows for dangerous levels of ozone and other dangerous compounds.[20]

Smog boven mexico city november 1985
A NASA satellite image of smog in the Valley of Mexico in November 1985

While still considered one of the most polluted places on the planet, the valley's air pollution problems are not as bad as they were several decades ago.[20] One major problem that was brought under control was the lead contamination in the air with the introduction of unleaded gasoline. Two other contaminants that have been brought under control are carbon monoxide and sulfur dioxide.[20] The contamination problems that remain are primarily with ozone and fine particles (soot) (between 2.5 micrometers and 10 micrometers).[19][20] Thirty to fifty percent of the time, Mexico City's levels of fine particles of ten micrometers, the most dangerous, exceed levels recommended by the World Health Organization.[19] In the 1940s, before large-scale burning of fossil fuels in the area, the visibility of the valley was about 100 km (60 mi), allowing for daily viewing of the mountain ranges that surround the valley, including the snow-capped volcanoes of Popocatepetl and Iztaccihuatl. Since that time, the average visibility has come down to about 1.5 km (5,000 ft). Mountain peaks are now rarely visible from the city itself.[6] While reduced visibility in the valley was due to sulfur emissions in the past, it is now due to fine particles in the air.[10]

The effects on humans living in an enclosed, contaminated environment have been documented, especially by Nobel Prize winner Dr Mario J. Molina. He claims fine particle pollution is the greatest concern because of lung damage.[20] According to him, the city's residents lose about 2.5 million working days every year due to health problems associated with fine particles.[19]

Hydrology

The Valley of Mexico is a closed basin which geologically divides into three hydrologic zones, the low plain, which is essentially the bed of now-extinct lakes, the piedmont area and the surrounding mountains. The old lakebeds correspond to the lowest elevations of the valley in the south are mostly clay with a high water content and are almost entirely covered by urban development.[4] In the piedmont area, these clays become mixed with silts and sands, and in some areas close to the mountains, the piedmont is largely composed of basalt from old lava flows. The valley is enclosed completely by mountain ranges, from which flow rain and melting snow into the valley's hydraulic system. This groundwater flow produces a number of springs in the foothills and upwellings in the valley floor.[4] This underground flow is the source of the five aquifers that provide much of the drinking water to Mexico City located in Soltepec, Apan, Texcoco, Chalco-Amecameca and underneath Mexico City itself.[3]

Old lake system

Lake Chalco 1847
An 1847 map of Lake Xochimilco and Lake Chalco

Before the 20th century, the Mexico City portion of the valley contained a series of lakes, with saline lakes to the north near the town of Texcoco and freshwater ones to the south.[4] The five lakes, Zumpango, Xaltoca, Xochimilco, Chalco, and the largest, Texcoco used to cover about 1,500 km2 (580 sq mi) of the basin floor.[2] Small mountains such as the Sierra de Guadalupe and Mount Chiconaultla partially separated the lakes from each other.[21] All the other lakes flowed toward the lower Lake Texcoco, which was saline due to evaporation.[2] The lakes were fed by a number of rivers such as the San Joaquin, San Antonio Abad, Tacubaya, Becerra, Mixcoac and Magdalena Contreras, carrying runoff and snowmelt from the mountains.[2]

Long before the arrival of the Spanish, the lake system had been shrinking due to climate change.[11] Warmer temperatures had increased evaporation and reduced rainfall in the area so that the lakes’ waters were shallow at about five meters (16 ft) deep as early as the Tlapacoya culture, around 10,000 BCE.[11] During the Aztec Empire, the northern lakes were inaccessible by canoe during the dry season from October to May.[9]

History of water control in the valley

For 2000 years, humans have been interfering with and altering the hydraulic conditions of the valley, especially in the lakes region.[11] The Aztecs built dikes for flood control and to separate the saline water of the northern lakes from the fresh water of the southern ones. After the destruction of Tenochtitlan in 1521, the Spaniards rebuilt the Aztec dikes but found they did not offer enough flood protection.[22]

The arrival of the Spanish and subsequent efforts to drain the area for flood control was a major infrastructure project, called the desagüe, was pursued the entire colonial period.[23][24][25][26][27]

The idea of opening drainage canals first came about after a flood of the colonial city in 1555. The first canal was begun in 1605 to drain the waters of Lake Zumpango north through Huehuetoca which would also divert waters from the Cuautitlán River away from the lakes and toward the Tula River. This project was undertaken by Enrico Martínez and he devoted 25 years of his life to it. He did succeed in building a canal in this area, calling it Nochistongo, leading waters to the Tula Valley, but the drainage was not sufficient to avoid the Great Flood of 1629 in the city. Another canal, which would be dubbed the "Grand Canal" was built parallel to the Nochistongo one ending in Tequixquiac. The Grand Canal consists of one main canal, which measures 6.5 meters (21 ft) in diameter and 50 km (30 mi) long.[28] The drainage project was continued after independence, with three secondary canals, built between 1856 and 1867. During the presidency of Porfirio Díaz (r. 1876–1911) drainage again became a priority.[29][30][31] Díaz completed it officially in 1894, although work continued thereafter.[22] Despite the Grand Canal's drainage capacity, it did not solve the problem of flooding in the city.

From the beginning of the 20th century, Mexico City began to sink rapidly and pumps needed to be installed in the Grand Canal, which before had drained the valley purely with gravity.[22] Along with the pumps, the Grand Canal was expanded with a new tunnel through the low mountains called the Xalpa to take the canal past Tequisquiac.[21] Even so, the city still suffered floods in 1950 and 1951.[22] Despite its age, the Grand Canal can still carry 2,400,000 US gallons per minute (150 m3/s) out of the valley, but this is significantly less than what it could carry as late as 1975 because continued sinking of the city (as much as 7 metres or 23 feet) weakens the system of water collectors and pumps.[22][32]

As a result, another tunnel, called the Emisor Central, was built to carry wastewater. Although it is considered the most important pipe in the country, it has been damaged by overuse and corrosion of its 20 ft (6 m) diameter walls.[32] Because of lack of maintenance and gradual decrease in this tunnel's ability to carry water, there is concern that this tunnel will soon fail. It is continuously filled with water, making it impossible to inspect it for problems. If it fails, it would most likely be during the rainy season when it carries the most water, which would cause extensive flooding in the historic center, the airport and the boroughs on the east side.[33]

Because of this, another new drainage project is planned that will cost $1.3 billion USD. The project includes new pumping stations, a new 30-mile (50 km) drainage tunnel and repairs to the current 7,400-mile (11,900 km) system of pipes and tunnels to clear blockages and patch leaks.[32][34]

Over-pumping of groundwater in the 20th century has hastened the disappearance of the lakes. The old lake beds are almost all paved[2] except for some canals preserved in Xochimilco, mostly for the benefit of visitors who tour them on brightly painted trajineras, boats similar to gondolas.[35]

Desiccation has had a major environmental impact on the Valley of Mexico.[36][37][38]

Drinking water and sinking lands

Angel am ex
The Independence Angel statue: street level has sunk below the bottom of the statue.

Historically, Mexico City's potable water supply came via aqueduct from the mountain springs on the valley sides like that in Chapultepec as most of the water in Lake Texcoco was saline.[2] These were originally built by the Aztecs and were rebuilt by the Spaniards. In the mid-1850s, potable groundwater was found underneath the city itself, which motivated the large-scale drilling of wells. Today, 70% of Mexico City's water still comes from five principal aquifers in the valley. These aquifers are fed by water from natural springs and runoff from precipitation.

It was only when the population reached about six million that Mexico City started to need to appropriate water from outside the valley.[2] Today, Mexico City faces a serious water deficit. Because of increased demand from a growing population, increasing industry, and ecosystem degradation in the form of deforestation of the surrounding mountains, more water is leaving the system than is entering. It is estimated that 63 cubic meters per second (1,000,000 US gal/min) of water is needed to support the potable and agricultural irrigation needs of Mexico City's population.[2] The main aquifer is being pumped at a rate of 55.5 m3/s (880,000 US gal/min), but is only being replaced at 28 m3/s (440,000 US gal/min), or about half of the extraction rate, leaving a shortfall of 27.5 m3/s (436,000 US gal/min).[2] This over-extraction of groundwater from the old clay lake bed has been causing the land upon which the city rests to collapse and sink. This problem began in the early 20th century as a consequence of the drainage of the valley for flood control. Since the beginning of the 20th century, some areas of Mexico City have sunk nine meters (30 ft).[2] In 1900, the bottom of the lake was three meters (10 ft) lower than the median level of the city center. By 1974, the lake bottom was two meters (7 ft) higher than the city.[4] The first signs of dropping ground water levels was the drying up of natural springs in the 1930s, which coincides with the beginning of intensive exploitation of the aquifer system through wells between 100 and 200 meters (330 and 660 ft) deep.[4] Today, Mexico City is sinking between five and forty centimeters (0.2 and 1.3 ft) per year, and its effects are visible.[2] El Ángel de la Independencia ("The Angel of Independence") statue, located on Paseo de la Reforma was built in 1910, anchored by a foundation deep beneath what was the surface of the street at that time. However, because the street has sunk around it, steps have been added to allow access to the statue's base.[2]

Subsidence of the valley floor beneath has caused flooding problems as now much of the city has sunk below the natural lake floor. Currently, pumps need to work 24 hours a day all year round to keep control of runoff and wastewater.[2] Despite this, flooding is still common, especially in the summer rainy season, in lower-lying neighborhoods such as Iztapalapa, forcing residents to build miniature dikes in front of their houses to prevent heavily polluted rainwater from entering their homes.[32] Subsidence also causes damage to water and sewer lines, leaving the water distribution system vulnerable to contamination which carries risks to public health.[4] Measures other than drainage have been implemented to contain flooding in the city. In 1950, dikes were built to confine storm runoff.[4] Rivers that run through the city were encapsulated in 1950 and 1951.[22] Rivers such as the Consulado River, Churubusco River and the Remedio River are encased in concrete tunnels which take their waters directly to the drainage system to leave the Valley. Two other rivers, the San Javier and the Tlalnepantla, which used to feed the old lake system, are diverted before they reach the city and their waters now flow directly into the Grand Canal.[39] None of water from these rivers is allowed to sink into the ground to recharge the aquifer. While the rivers and streams that flow down from the mountain peaks still begin the way they always have, their passage through the shantytowns lacking city sanitation schemes that surround Mexico City turns them into open combined sewers. Therefore, their final stages are frequently culverted or added to the existing major culverted rivers to keep this water from contaminating the aquifer.[39]

See also

References

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  2. ^ a b c d e f g h i j k l m n o p q r s t u v w x "Mexico City: Opportunities and Challenges for Sustainable Management of Urban Water Resources". December 2004. Archived from the original on 2008-12-07. Retrieved 2008-11-25.
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  5. ^ Noted in passing by Christian Lévêque, Biodiversity Dynamics and Conservation: The Freshwater Fish of Tropical Africa, 1997 "Introduction" p. xi.
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  30. ^ Perló Cohen, Manuel (1999). El paradigma porfiriano: Historia del desagüe del Valle de México [The Porfirian paradigm: A history of the drainage of the Valley of Mexico]. Mexico City: Porrúa.
  31. ^ Agostoni, Claudia (2003). Monuments of Progress: Modernization and Public Health in Mexico City, 1876–1910. Calgary: University of Calgary Press.
  32. ^ a b c d Ellingwood, Ken (April 28, 2008). "Draining the basin that's Mexico City". Los Angeles Times. Retrieved 25 November 2008.
  33. ^ Stevenson, Mark (2007-06-19). "Mexico City Faces Threat of Floods". Fox News. Associated Press. Archived from the original on March 4, 2016. Retrieved 25 November 2008.
  34. ^ "Mexico announces US$1.27 billion drain tunnel". Associated Press. August 13, 2008. Retrieved 25 November 2008.
  35. ^ "Mexico City's 'water monster' nears extinction". Beijing: China Daily. Associated Press. November 2, 2008. Retrieved 25 November 2008.
  36. ^ Romero Lankao, Patricia (1999). Obra hidráulica de la ciudad de México y su impacto socioambiental. Mexico City: Instituto Mora.
  37. ^ Aboites Aguilar, Luis (1998). El agua de la nación: Una historia política de México (1888–1946) [The nation's water: A political history of Mexico (1888–1946)]. Mexico City: Centro de Investigación y Estudios Superiores en Antropología Social.
  38. ^ Villaseñor, Alejandro Tortolero (1996). Tierra, agua, y bosques: Historia y medio ambiente en el México central [Earth, water and woodland: An environmental history of Central Mexico]. Mexico City: Potrerillos.
  39. ^ a b Benitez, Fernando (1984). Historia de la Ciudad de Mexico (in Spanish). 9. Mexico City: SALVAT. pp. 46–47. ISBN 968-32-0209-8.

Coordinates: 19°40′N 98°52′W / 19.667°N 98.867°W

Altepetl

The altepetl (Classical Nahuatl: āltepētl [aːɬ.ˈté.peːtɬ]) or modern pronunciation , in pre-Columbian and Spanish conquest-era Aztec society, was the local, ethnically-based political entity, usually translated into English as "city-state". The word is a combination of the Nahuatl words ātl (meaning "water") and tepētl (meaning "mountain"). A characteristic Nahua mode was to imagine the totality of the people of a region or of the world as a collection of altepetl units and to speak of them on those terms. The concept is comparable to Maya cah and Mixtec ñuu.

Axolotl

The axolotl (, from Classical Nahuatl: āxōlōtl [aːˈʃoːloːtɬ] (listen); plural axolotls or rarely axolomeh), Ambystoma mexicanum, also known as the Mexican walking fish, is a neotenic salamander related to the tiger salamander. Although the axolotl is colloquially known as a "walking fish", it is not a fish, but an amphibian. The species was originally found in several lakes, such as Lake Xochimilco underlying Mexico City. Axolotls are unusual among amphibians in that they reach adulthood without undergoing metamorphosis. Instead of developing lungs and taking to the land, adults remain aquatic and gilled.

Axolotls should not be confused with waterdogs, the larval stage of the closely related tiger salamanders (A. tigrinum and A. mavortium), which are widespread in much of North America and occasionally become neotenic. Neither should they be confused with mudpuppies (Necturus spp.), fully aquatic salamanders that are not closely related to the axolotl but bear a superficial resemblance.As of 2010, wild axolotls were near extinction due to urbanization in Mexico City and consequent water pollution, as well as the introduction of invasive species such as tilapia and perch. They are currently listed by CITES as an endangered species and by IUCN as critically endangered in the wild, with a decreasing population. Axolotls are used extensively in scientific research due to their ability to regenerate limbs. Axolotls were also sold as food in Mexican markets and were a staple in the Aztec diet.Surveys in 1998, 2003, and 2008 found 6,000, 1,000, and 100 axolotls per square kilometer in its Lake Xochimilco habitat, respectively. A four-month-long search in 2013, however, turned up no surviving individuals in the wild. Just a month later, two wild ones were spotted in a network of canals leading from Xochimilco. The city is currently working on conserving axolotls by building "axolotl shelters" and conserving remaining and potential habitats for the salamanders.

Aztecs

The Aztecs () were a Mesoamerican culture that flourished in central Mexico in the post-classic period from 1300 to 1521. The Aztec peoples included different ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl language and who dominated large parts of Mesoamerica from the 14th to the 16th centuries. Aztec culture was organized into city-states (altepetl), some of which joined to form alliances, political confederations, or empires. The Aztec empire was a confederation of three city-states established in 1427, Tenochtitlan, city-state of the Mexica or Tenochca; Texcoco; and Tlacopan, previously part of the Tepanec empire, whose dominant power was Azcapotzalco. Although the term Aztecs is often narrowly restricted to the Mexica of Tenochtitlan, it is also broadly used to refer to Nahua polities or peoples of central Mexico in the prehispanic era, as well as the Spanish colonial era (1521–1821). The definitions of Aztec and Aztecs have long been the topic of scholarly discussion, ever since German scientist Alexander von Humboldt established its common usage in the early nineteenth century.Most ethnic groups of central Mexico in the post-classic period shared basic cultural traits of Mesoamerica, and so many of the traits that characterize Aztec culture cannot be said to be exclusive to the Aztecs. For the same reason, the notion of "Aztec civilization" is best understood as a particular horizon of a general Mesoamerican civilization. The culture of central Mexico includes maize cultivation, the social division between nobility (pipiltin) and commoners (macehualtin), a pantheon (featuring Tezcatlipoca, Tlaloc and Quetzalcoatl), and the calendric system of a xiuhpohualli of 365 days intercalated with a tonalpohualli of 260 days. Particular to the Mexica of Tenochtitlan was the patron God Huitzilopochtli, twin pyramids, and the ceramic ware known as Aztec I to IV.From the 13th century, the Valley of Mexico was the heart of dense population and the rise of city-states. The Mexica were late-comers to the Valley of Mexico, and founded the city-state of Tenochtitlan on unpromising islets in Lake Texcoco, later becoming the dominant power of the Aztec Triple Alliance or Aztec Empire. It was a tributary empire that expanded its political hegemony far beyond the Valley of Mexico, conquering other city states throughout Mesoamerica in the late post-classic period. It originated in 1427 as an alliance between the city-states Tenochtitlan, Texcoco, and Tlacopan; these allied to defeat the Tepanec state of Azcapotzalco, which had previously dominated the Basin of Mexico. Soon Texcoco and Tlacopan were relegated to junior partnership in the alliance, with Tenochtitlan the dominant power. The empire extended its reach by a combination of trade and military conquest. It was never a true territorial empire controlling a territory by large military garrisons in conquered provinces, but rather dominated its client city-states primarily by installing friendly rulers in conquered territories, by constructing marriage alliances between the ruling dynasties, and by extending an imperial ideology to its client city-states. Client city-states paid tribute to the Aztec emperor, the Huey Tlatoani, in an economic strategy limiting communication and trade between outlying polities, making them dependent on the imperial center for the acquisition of luxury goods. The political clout of the empire reached far south into Mesoamerica conquering polities as far south as Chiapas and Guatemala and spanning Mesoamerica from the Pacific to the Atlantic oceans.

The empire reached its maximal extent in 1519, just prior to the arrival of a small group of Spanish conquistadors led by Hernán Cortés. Cortés allied with city-states opposed to the Mexica, particularly the Nahuatl-speaking Tlaxcalteca as well as other central Mexican polities, including Texcoco, its former ally in the Triple Alliance. After the fall of Tenochtitlan on August 13, 1521 and the capture of the emperor Cuauhtemoc, the Spanish founded Mexico City on the ruins of Tenochtitlan. From there they proceeded with the process of conquest and incorporation of Mesoamerican peoples into the Spanish Empire. With the destruction of the superstructure of the Aztec Empire in 1521, the Spanish utilized the city-states on which the Aztec Empire had been built, to rule the indigenous populations via their local nobles. Those nobles pledged loyalty to the Spanish crown and converted, at least nominally, to Christianity, and in return were recognized as nobles by the Spanish crown. Nobles acted as intermediaries to convey tribute and mobilize labor for their new overlords, facilitating the establishment of Spanish colonial rule.Aztec culture and history is primarily known through archaeological evidence found in excavations such as that of the renowned Templo Mayor in Mexico City; from indigenous writings; from eyewitness accounts by Spanish conquistadors such as Cortés and Bernal Díaz del Castillo; and especially from 16th- and 17th-century descriptions of Aztec culture and history written by Spanish clergymen and literate Aztecs in the Spanish or Nahuatl language, such as the famous illustrated, bilingual (Spanish and Nahuatl), twelve-volume Florentine Codex created by the Franciscan friar Bernardino de Sahagún, in collaboration with indigenous Aztec informants. Important for knowledge of post-conquest Nahuas was the training of indigenous scribes to write alphabetic texts in Nahuatl, mainly for local purposes under Spanish colonial rule. At its height, Aztec culture had rich and complex mythological and religious traditions, as well as achieving remarkable architectural and artistic accomplishments.

Chicomoztoc

Chicomoztoc ([t͡ʃikoˈmostok]) is the name for the mythical origin place of the Aztec Mexicas, Tepanecs, Acolhuas, and other Nahuatl-speaking peoples (or Nahuas) of the central Mexico region of Mesoamerica, in the Postclassic period.

There is an association of Chicomoztoc with certain legendary traditions concerning Culhuacan (Colhuacan), an actual pre-Columbian settlement in the Valley of Mexico which was considered to have been one of the earliest and most pre-eminent settlements in the valley. Culhuacan ("place of those with ancestors" is its literal meaning in Classical Nahuatl) was viewed as a prestigious and revered place by the Aztec/Mexica (who also styled themselves 'Culhua-Mexica'). In Aztec codical writing, the symbol or glyph representing the toponym of Culhuacan took the form of a 'bent' or 'curved' hill (a play on the homonym col- in Nahuatl, meaning "bent, twisted", e.g. as if by old age).

Some researchers have attempted to identify Chicomoztoc with a specific geographic location, likely between 60 and 180 miles northeast of the Valley of Mexico including perhaps a height near the present-day town of San Isidro Culhuacan. The purported existence of actual caves plays a role in New Age Mayanism.

Cuicuilco

Cuicuilco is an important archaeological site located on the southern shore of Lake Texcoco in the southeastern Valley of Mexico, in what is today the borough of Tlalpan in Mexico City. The settlement goes back to 1400 BC.Cuicuilco flourished during the Mesoamerican Middle and Late Formative (c. 700 BCE – 150 CE) periods.

Today, it is a significant archaeological site that was occupied during the Early Formative until its destruction in the Late Formative. Based on its date of occupation, Cuicuilco may be the oldest city in the Valley of Mexico and was roughly contemporary with, and possibly interacting with, the Olmec of the Gulf Coast of lowland Veracruz and Tabasco (also known as the Olmec heartland).

Freemasonry in Mexico

The history of Freemasonry in Mexico can be traced to at least 1806 when the first Masonic lodge was formally established in the nation.

Many presidents of Mexico were Freemasons. Freemasonry has greatly influenced political actions in the early republic, as holder of conservative ideas gathered in lodges of the Scottish Rite, while reformists choose the York Rite. Hence escoceses became synonymous with Conservatives, and yorkinos with Liberals. Santa Anna was a Scottish Rite Mason.

Greater Mexico City

Greater Mexico City refers to the conurbation around Mexico City, officially called Valley of Mexico Metropolitan Area (Zona Metropolitana del Valle de México), constituted by Mexico City itself composed of 16 Municipalities—and 41 adjacent municipalities of the states of Mexico and Hidalgo. For normative purposes, however, Greater Mexico City most commonly refers to the Metropolitan Area of the Valley of Mexico (Zona Metropolitana del Valle de México) an agglomeration that incorporates 18 additional municipalities. As of 2016 an estimated 21,157,000 people lived in Greater Mexico City, making it the largest metropolitan area in North America. It is surrounded by thin strips of highlands which separate it from other adjacent metropolitan areas, of which the biggest are Puebla, Toluca, and Cuernavaca-Cuautla, and together with which it makes up the Mexico City megalopolis.

Since the 1940s there have been different proposals to establish the limits of the growing conurbation of Mexico City, and different definitions were used unofficially as the city continued to grow. The Federal Government (represented by the Department of Social Development), the government of Mexico City, and the government of the State of Mexico agreed on the official definitions for both the Mexico City Metropolitan Area and the Metropolitan Area of the Valley of Mexico on 22 December 2005. Per the agreement, most urban planning projects will be administered by Metropolitan Commissions.

On January 29, 2016, Mexico City proper was no longer called the Federal District (Spanish: "Distrito Federal" or D.F.). It is now in transition to become the country's 32nd federal entity, officially "City of Mexico" (Spanish: "Ciudad de México", commonly abbreviated as "CDMX"), giving it a level of autonomy comparable to that of a state. Because of a clause in the Mexican Constitution, however, since it is the seat of the powers of the federation, it can never become a state, or the capital of the country has to be relocated. The English name "Mexico City" remains. Its original 16 "Boroughs" became "municipalities".

History of the Aztecs

The Aztecs were a Pre-Columbian Mesoamerican people of central Mexico in the 14th, 15th and 16th centuries. They called themselves Mexicah (pronounced [meˈʃikaʔ]).

The capital of the Aztec Empire was Tenochtitlan. During the empire, the city was built on a raised island in Lake Angels. Modern-day Mexico City was constructed on the ruins of Tenochtitlan. The Spanish colonisation of the Americas reached the mainland during the reign of Hueyi Tlatoani Moctezuma II (Montezuma II). In 1521, Hernán Cortés, along with an allied army of other Native Americans, conquered the Aztecs through germ warfare (germ theory not being established until 1560 by earliest records, this was an unintentional result of Europeans coming to the New World), siege warfare, psychological warfare, and from direct combat.

From 1376 until 1572, the Mexicah were a tributary of Azcapotzalco. The Aztec rulers Acamapichtli, Huitzilihuitl and Chimalpopoca were, in fact, vassals of Tezozomoc, the Tepanec ruler of Azcapotzalco.

When Tezozomoc died in 1421, his son Malazia ascended to the throne of Azcapotzalco. Matla (nick name) sought to tighten Azcapotzalco's grip on the nearby city-states in the Valley of Mexico. In the process, Chimalpopoca, tlatoani of Tenochtitlan, was assassinated by Maxtla's agents while Nezahualcoyotl of Texcoco was forced into exile.

Lake Texcoco

Lake Texcoco (Spanish: Lago de Texcoco) was a natural lake within the "Anahuac" or Valley of Mexico. Lake Texcoco is best known as where the Aztecs built the city of Tenochtitlan, which was located on an island within the lake. After the Spanish conquest of the Aztec Empire, efforts to control flooding by the Spanish led to most of the lake being drained. The entire lake basin is now almost completely occupied by Mexico City, the capital of the present-day nation of Mexico.

Mexica

The Mexica (Nahuatl: Mēxihcah, Nahuatl pronunciation: [meːˈʃiʔkaʔ] (listen) (singular Mēxihcatl [meːˈʃiʔkat͡ɬ]) or Mexicas were a Nahuatl-speaking indigenous people of the Valley of Mexico who were the rulers of the Aztec Empire. This group was also known as the Culhua-Mexica in recognition of its kinship alliance with the neighboring Culhua, descendants of the revered Toltecs, who occupied the Toltec capital of Tula from the tenth through twelfth centuries. The Mexica were additionally referred to as the "Tenochca", a term associated with the name of their altepetl (city-state), Tenochtitlan, and Tenochtitlan's founding leader, Tenoch. The Mexica established Mexico Tenochtitlan, a settlement on an island in Lake Texcoco. A dissident group in Mexico-Tenochtitlan separated and founded the settlement of Mexico-Tlatelolco with its own dynastic lineage. The name Aztec was coined by Alexander von Humboldt who combined "Aztlan" ("place of the heron"), their mythic homeland, and "tec(atl)", 'people of'. The term Aztec is often used very broadly to refer not only to the Mexica, but also to the Nahuatl-speaking peoples or Nahuas of the Valley of Mexico and neighboring valleys.

Tenochtitlan

Tenochtitlan (Nahuatl languages: Tenōchtitlan pronounced [tenoːt͡ʃˈtit͡ɬan]; Spanish: Tenochtitlán), also known as Mexica-Tenochtitlan (Nahuatl languages: Mēxihco Tenōchtitlan pronounced [meːˈʃiʔko tenoːt͡ʃˈtit͡ɬan]; Spanish: México-Tenochtitlán), was a large Mexica city-state in what is now the center of Mexico City. The exact date of the founding of the city is unclear, but the most commonly accepted date is March 13, 1325. The city was built on an island in what was then Lake Texcoco in the Valley of Mexico. The city was the capital of the expanding Aztec Empire in the 15th century until it was captured by the Spanish in 1521.

At its peak, it was the largest city in the pre-Columbian Americas. It subsequently became a cabecera of the Viceroyalty of New Spain. Today, the ruins of Tenochtitlan are in the historic center of the Mexican capital. The World Heritage Site of Xochimilco contains what remains of the geography (water, boats, floating gardens) of the Mexica capital.

Tenochtitlan was one of two Mexica āltēpetl (city-states or polities) on the island, the other being Tlatelolco.

Tepanec

The Tepanecs or Tepaneca are a Mesoamerican people who arrived in the Valley of Mexico in the late 12th or early 13th centuries. The Tepanec were a sister culture of the Aztecs (or Mexica) as well as the Acolhua and others—these tribes spoke the Nahuatl language and shared the same general pantheon, with local and tribal variations.

The name "Tepanecas" is a derivative term, corresponding to their original mythical city, Tepanohuayan (the passing by), also known as Tepano. Ideographically it is represented as a stone, for its etymology comes from Tepan (over the stones). Their conquered territories received the name Tepanecapan (land of the tepanecas) (lit. "over the tepanecas").

Reputedly welcomed to the Valley of Mexico by the semi-legendary Chichimec ruler Xolotl, the Tepanecs settled on the west shores of Lake Texcoco. Under their tlatoani, Acolnahuacatl, the Tepanec took over Azcapotzalco from the indigenous inhabitants. In the early 14th century, Tezozomoc brought the Tepanec to the height of their power; at that point they controlled nearly all of the Valley of Mexico as well as parts of the Toluca and Morelos valleys. Native sources say that Tezozomoc lived to the age of over 100 and was legendary for his generalship and statesmanship.

The death of Tezozomoc in 1426 brought his sons Tayatzin and Maxtla to the throne, with Maxtla most likely poisoning Tayatzin. In 1428, Maxtla was overthrown by the nascent Aztec Triple Alliance, which included the Mexicas of Tenochtitlan and the Acolhua of Texcoco, as well as Maxtla's fellow Tepanecs of Tlacopan. With the rise of the Aztec empire, Tlacopan became the predominant Tepanec city, although both Tenochtitlan and Texcoco eclipsed Tlacopan in size and prestige.

According to the tradition recompiled by several historians, the Tepanec people constituted one of the seven tribes that started the migration from Chicomoztoc (in nahuatl, "The Seven Caves"); a place which has no certain location, and while, during the middle of the 20th century, the general opinion was that La Quemada had to be the place, in the opinion of later investigators the city must've been north of the Valley of Mexico, or towards the ancient Tula, even in the Chiconauhtla hill, south of Teotihuacan). To the Tepaneca tribe belonged, by their military might, one of the best zones where they founded Azcapotzalco main Altepetl of their territory, known as Tepanecapan.

When the Spaniard conquistadores arrived to the Valley of Mexico, the Tepaneca tribe was subject to the Triple Alliance, led by Tenochtitlan, not able to remain as an ethnic group. We know of their existence thanks to references in stories derived from the prehispanic codex traditions, which were compiled by novohispanic historians.

Tepetlaoztoc

Tepetlaoztoc or Tepetlaoxtoc (Nahuatl for "tepetate-cave place", modern Nahuatl pronunciation ) is an archaeological site located in the Central Mexico plateau region of Mesoamerica, which was an Aztec/Nahua settlement during the Late Postclassic period of Mesoamerican chronology, with an occupancy continuing through the Colonial period. The site is situated in the Valley of Mexico, to the northeast of Texcoco.

In the 1970s the area was relatively undeveloped, and one could, on aerial photographs, still discern the 16th century field lines and irrigation system drawn in the Codex of Santa María Asunción (manuscript in the Biblioteca Nacional) and the Codex Vergara. Likewise one could locate many of the aldeas that were tributary to Tepetlaoztoc, and still find the wall bases of their houses. By the time of William T. Sanders's work in the 1990s, development had largely destroyed these remnants.

Texcoco (altepetl)

Texcoco (Classical Nahuatl: Tetzco(h)co pronounced [tetsˈkoʔko]) was a major Acolhua altepetl (city-state) in the central Mexican plateau region of Mesoamerica during the Late Postclassic period of pre-Columbian Mesoamerican chronology. It was situated on the eastern bank of Lake Texcoco in the Valley of Mexico, to the northeast of the Aztec capital, Tenochtitlan. The site of pre-Columbian Texcoco is now subsumed by the modern Mexican municipio of Texcoco and its major settlement, the city formally known as Texcoco de Mora. It also lies within the greater metropolitan area of Mexico City.

Pre-Columbian Texcoco is most noted for its membership in the Aztec Triple Alliance. At the time of the Spanish conquest of Mexico, it was one of the largest and most prestigious cities in central Mexico, second only to the Aztec capital, Tenochtitlan. A survey of Mesoamerican cities estimated that pre-conquest Texcoco had a population of 24,000 and occupied an area of 450 hectares.The people of Tetzcohco were called Tetzcocatl [tet͡sˈkokat͡ɬ] (singular) or Tetzcocah [tet͡sˈkokaʔ] (plural).

Tizayuca

Tizayuca is one of the 84 municipalities of Hidalgo, in central-eastern Mexico. The city of Tizayuca is the municipal seat.

Tlacopan

Tlacopan (meaning "florid plant on flat ground"), also called Tacuba, was a Pre-Columbian Mesoamerican city-state situated on the western shore of Lake Texcoco on the site of today's neighborhood of Tacuba in Mexico City. Nearby was the city of Tiliuhcan.

Tlatelolco (altepetl)

Tlatelolco (Classical Nahuatl: Mēxihco-Tlatelōlco [tɬateˈloːɬko], modern Nahuatl pronunciation ) (also called Mexico Tlatelolco) was a prehispanic altepetl or city-state, in the Valley of Mexico. Its inhabitants were known as Tlatelolca. The Tlatelolca were a part of the Mexica, a Nahuatl-speaking people who arrived in what is now central Mexico in the 13th century. The Mexica settled on an island in Lake Texcoco, founding the altepetl of Mexico-Tenochtitlan on the southern portion of the island. In 1337, a group of dissident Mexica broke away from the Tenochca leadership in Tenochtitlan and founded Mexico-Tlatelolco on the northern portion of the island. Tenochtitlan was closely tied with its sister city, which was largely dependent on the market of Tlatelolco, the most important site of commerce in the area.

Tlatilco culture

Tlatilco culture is a culture that flourished in the Valley of Mexico between the years 1250 BCE and 800 BCE, during the Mesoamerican Early Formative period. Tlatilco, Tlapacoya, and Coapexco are the major Tlatilco culture sites.

Tlatilco culture shows a marked increase in specialization over earlier cultures, including more complex settlement patterns, specialized occupations, and stratified social structures. In particular, the development of the chiefdom centers at Tlatilco and Tlapacoya is a defining characteristic of Tlatilco culture.

This period also saw a significant increase in long distance trade, particularly in iron ore, obsidian, and greenstone, trade which likely facilitated the Olmec influence seen within the culture, and may explain the discovery of Tlatilco-style pottery near Cuautla, Morelos, 90 miles (140 km) to the south.

Tren Suburbano

The Suburban Railway of the Valley of Mexico Metropolitan Area (Spanish: Ferrocarril Suburbano de la Zona Metropolitana del Valle de México) is an electric suburban rail system in Mexico City. It is also known as Valley of Mexico Suburban Rail System and colloquially referred to as El Tren Suburbano. It is designed to complement the extensive Mexico City metro system, Latin America's largest and busiest urban rail network.

There are projects to expand in progress and new proposals to expand the total length of the rail system to 242 kilometres (150 mi). The new projects to expand the network will include expansion into the adjacent state of Mexico.

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