Early farmers achieved an “engineering wonder of the world” by building a giant irrigation system in South America thousands of years ago.
Communities living in what is now Colombia created the remarkable network based on cooperation among family groups—without top-down government—according to a new study.
The researchers believe modern policymakers could adopt a similar strategy to solve the country’s current water management crisis.
These pre-Hispanic watering systems of La Mojana in northern Colombia are so vast you can see them from an aircraft at high altitude.
Their canals and raised fields—in use from the first centuries BC until the 11th Century AD—cover an astonishing 1,930 square-miles (500,000 hectares), three times the size of London today, according to a University of Cambridge media release.
It has traditionally been assumed that powerful rulers must have ordered and managed such an ambitious infrastructure project because of its complexity and the amount of work thought to be involved.
But the new study, led by University archaeologists, suggests that the work was most likely locally-led, cooperative, and much faster than previously assumed.
The team said their findings, published in the journal Communications Sustainability, are important historically but also offer hope to Colombians today who are suffering from a water management crisis linked to climate change.
“These field systems are so impressive that people have assumed they were achieved by hierarchical chiefdoms,” said study lead author Dr. Jasmine Vieri, from Cambridge.
“Our findings indicate that local communities were capable of building these systems and organizing themselves.”
She says the societies responsible for the hydraulic systems in La Mojana were contemporary with the Maya, and with the broader Mesoamerican and Andean state-level societies, which culminated in the Aztec and Inca empires a few centuries later.
They occupied an area where there is no evidence of state-level societies, despite evidence of elaborate gold work and ceramics, and the new findings support the idea that the people, choosing to organize themselves far more horizontally, were able to achieve great things.
Their raised field system managed huge quantities of water during heavy rains, gradually redirected it in drier months, buffering against both drought and floods.
The network of canals redistributed water from permanent bodies of water around raised areas of housing.
The system provided more fertile soils for cultivation in dry seasons and may have helped locals to trap fish.
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Using satellite imagery, the researchers mapped a 500-hectare portion (around 700 football pitches) of Pre-Hispanic field systems in the municipality of San Macros, Sucre.
They studied the infrastructure at an unprecedented level of detail, recording the dimensions and volume of 1,600 ridges and 63 housing platforms.
The team worked out that, when first constructed, the formations were around 1.4 meters (4.6 ft) high from the top of the ridge to the lowest point of the canal.
The researchers then developed a new method to quantify the labor needed to construct the system and factored-in volumes of moved earth, as well as information about local geology, indigenous working practices, population density and available technology.
Starting from an estimated population of 1,600 people in the study area, they based their calculations on a workforce of 800 people, given evidence that men, women and probably children traditionally engage in subsistence farming.
Soils in the Colombian Caribbean are heavy clay which would have made the work harder and there were no metal shovels in the region at the time.
“Pre-Hispanic societies were inventive and cooperative, they worked with nature rather than trying to obstruct it,” said study senior author Professor Marcos Martinon-Torres.
He said evidence for the use of raised field systems in the region ends before the Spanish arrived in the 16th Century. It isn’t clear why they stopped being used, but it has been suggested there was population movement from the lowlands towards mountainous areas.
The researchers say that such sustainable solutions to water management can be adopted today by local populations without the need for state intervention.
“Policymakers have shown interest in these ancient systems, but lacked data,” said study co-author Dr. Fernando Montejo Gaitán, from the Colombian Institute of Anthropology and History (ICANH),
“Our study is the first to show that these solutions can be organized locally. People may need resources from the state but not necessarily state intervention.”
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