Was it solely an adaptaption to their environment or was there already a similar practice in use by their neighbors? And was it used anywhere outside the valley of mexico? Did the high yield chinampas give the aztecs an edge over their competitors or was it mostly other factors?
The Postclassic chinampas that was used by the Aztecs developed from a long tradition of wetland farming and irrigation, one that pre-dated even Mesoamerican urbanism itself. Maize pollen found in swamps indicate that farming was occurring in or around wetlands before the Olmecs appeared. The advantages of doing so are obvious. Wetlands were naturally fertile, and the elevated moisture levels of their soils made manual irrigation unnecessary. Conversely, they also had a set of challenges which needed to be managed, the primary one being flooding. This would empower communities, which could manage water resources more effectively as a unit, ultimately contributing to the development of stratified states such as the Olmec city-states. The Olmecs, of course, lived in a region with plentiful water, so it is not surprising that they were some of the earliest people to use canal building and the like on a large scale. However, they were not the only ones. Formative period Maya people also exploited seasonal wetlands, for much the same reason. They constructed ‘basin-canals’, which were essentially swampy depressions, used to control water-flow, ease irrigation, and regulate water levels. Where swampland was not naturally occurring, Mesoamerican people created their own, using canals to move water around and facilitate irrigation. An example of this comes from the site of Edzna in Campeche, where Formative period Maya people built an extensive canal network, totalling around 20 kilometres in length, plus supporting reservoirs. The main canal was an impressive 12 kilometres long and may have been as much as 50 meters wide. It was probably used for both transport and for irrigation. Canals also provided another benefit. They became silt traps. The silt could then be hauled up onto neighbouring fields to act as a form of super-rich fertiliser. These techniques were, of course, not limited to the Gulf Coast or the Maya lowlands. Even in areas that were quite dry, such as Oaxaca, Indigenous communities invested heavily into irrigation and canal building wherever possible.
As populations grew during the Classic period, so did the scale and sophistication of their hydraulic systems. Teotihuacan sustained a portion of its massive population because of its irrigated fields, even going so far as to diver the course of the San Juan river to regulate flooding, and building storm water systems, to harness runoff from the urban centre and direct it into reservoirs for later use in agriculture. The Classic Maya cities often boasted some truly impressive water systems. The sites of Palenque, Tikal, and Copan, are among the most impressive, having extensive systems of aqueducts, reservoirs, and canals. Since most of these were located in the built-up parts of the cities, much of this water would have been reserved for domestic use, such as drinking and cleaning. Nevertheless, small kitchen gardens were common, and were almost certainly watered from these urban water systems. Furthermore, even though these systems are largely urban, their existence suggests that the Maya had the capability to build similar structures in their immediate agricultural hinterland. Although evidence of large-scale irrigation is harder to detect in the under-explored agricultural areas of the Classic Maya world, there is some strong evidence supporting this claim. The Belize River Valley is riddled with irrigation systems, while no fewer than 38 have been identified within the Puuc Hills. Undoubtedly, more are still waiting to be uncovered.
However, none of these are chinampas. And tracking down the origins of the chinampas is more difficult than it appears. However, historians generally track it to one of two places. The first is Xochimilco. This makes sense. Lake Xochimilco was the agricultural heartland of the Valley of Mexico, and it is where the chinampas were at their greatest extent. However, Xaltocan is also a potential candidate, as it also had an extensive chinampas and dyke system, one which pre-dated the Aztec’s rise to power. Either way, the chinampas appeared sometime during the Postclassic period, in the Valley of Mexico. The primary difference between the chinampas and earlier forms of wetland fields is the level of control over the water and amount of manipulation of the soil. Chinampas are not just fields, they are built up from the swampy lakebed in specific layers of substrate to control drainage and manage the water table. The canals around the lake are also deepened, straightened, and often regulated by dykes and other forms of flood control. This development is often associated with the increasing complexity of Postclassic Central Mexican states. Most likely, the two factors are related. As agricultural techniques became more sophisticated, they could support a more complex state. A more complex state could invest more resources into agricultural and water management systems. And vice-versa.
So that’s how the chinampas came to be. But what role did they play in the Mexica (Aztec) Empire? Quite a big one actually. While the chinampas was a widespread technique already, they were nowhere near as extensive as they would later become. After the Mexica conquered Xochimilco, they began a 40 year policy of expanding the chinampas there, ultimately building somewhere between 9,000 and 12,000 hectares of chinampas and canal. They also build the 16km long Dyke of Nezahualcoyotl, which blocked saline waters from eastern Lake Texcoco from flooding into the western half, effectively turning the water around Tenochtitlan into a freshwater lake. This allowed the Chinampas around the city and its neighbours to greatly expand. Although demographics of the Valley of Mexico are still debated, I think that these fields could have fed somewhere between 300,000 and 500,000 people when taken in aggregate. This is really important, because the Valley of Mexico, and the chinampas land in particular, was the Mexica Empires economic and political heartland. Its were they drew their military manpower from, and was home to the labour force that sustained its economy. I have no doubt that the policy of Chinampas building was one of the key parts of the Mexica Empire’s success.
As to chinampas in other regions, I’ve read the suggestion occasionally. One such place would be I the Valley of Toluca. However, I am not certain as to how well supported these claims are. So I’ll say that it is possible, but yet to be proven.
Sources:
Acuña, Helga Geovannini: - Rain Harvesting in the Rainforest: The Ancient Maya agricultural landscapes of Calakmul, Campeche, Mexico, (Oxford: Archaeopress, 2008)
Donkin, R.A.: - Agricultural Terracing in the Aboriginal New World, (Tucson: University of Arizona Press, 1973)
Doolittle, William E.: - Canal Irrigation in Prehistoric Mexico: The Sequence of Technological Change, (Austin: University of Texas Press, 1990)
Emery, Kitty F.: - (ed.), Maya Zooarchaeology: New Directions in Method and Theory, (Los Angeles: Cotsen Institute of Archaeology University of California, 2004)
Farrington, I.S.:
Fedick, Scott L.: - (ed.) The Managed Mosaic: Ancient Maya Agriculture and Resource Use, (Salt Lake City: University of Utah Press, 1996)
Flannery, Kent V.: - (ed.) Maya Subsistence: studies in memory of Dennis E. Puleston, (New York: Academic Press, 1982)
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Harvey, H.R.:
Lentz, David L.:
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Lucero, Lisa J., and Fash, Barbara W.:
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Sanders, William T., Parsons, Jeffrey R., and Santley, Robert S.: - The Basin of Mexico: Ecological Processes in the Evolution of a Civilization, (New York: Academic Press, 1979)