Ancient Colombian communities built a vast water management system covering about 500,000 hectares, or 1.2 million acres, without relying on powerful rulers to organize the work, according to a new study.
The network of canals and raised fields stretches across La Mojana in Colombia’s Caribbean region, covering an area roughly the size of Grand Canyon National Park and three times the size of London.
Researchers say local families likely built and maintained different parts of the system through cooperation. The finding challenges a long-standing assumption that such large infrastructure required centralized political control.
Communities used the system from the first centuries B.C. until about the 11th century A.D., managing water in a landscape shaped by seasonal floods and droughts. A similar approach has been documented in Belize, where archaeologists found evidence of wetland adaptation involving canals and raised fields used for farming and water management.
Satellite mapping reveals how quickly it was built
A University of Cambridge-led team used satellite imagery to study 500 hectares of the ancient landscape in San Marcos, Sucre.
Researchers mapped 1,600 raised ridges and 63 housing platforms. The structures originally measured about 1.4 meters, or 4.6 feet, from the top of a ridge to the lowest point of a canal.
The team then estimated the labor required to build the system, considering the amount of earth moved, heavy clay soils, population density, Indigenous working practices and available technology. Researchers estimated about 1,600 people lived in the study area and based their calculations on 800 workers.
The results suggest one canal-and-ridge system could have been completed in less than two months, or about half a dry season. “That’s a far lower labor investment than has been previously assumed, and manageable through cooperation,” lead author Jasmine Vieri of Cambridge’s McDonald Institute for Archaeological Research said.
Other ancient societies also reshaped landscapes on a remarkable scale. In Armenia, researchers mapped more than 1,000 kilometers of water-management features around ancient Armavir, revealing how engineered waterways supported farming and settlement.
Findings challenge ideas about political power
Archaeologists had previously associated the enormous field systems, elaborate ceramics and goldwork with hierarchical chiefdoms. The new study offers another explanation.
Researchers say evidence for state-level societies in La Mojana is lacking. Instead, communities may have organized major construction projects locally.
The water system itself was highly adapted to the environment. Canals managed excess water during heavy rains and redirected it during drier periods. Raised areas supported homes and cultivation, while the waterways may also have helped residents trap fish.
Similar evidence has emerged in Belize, where researchers identified a 4,000-year-old network of canals built by Maya predecessors that was likely used for fishing.
Ancient solution could offer lessons today
The findings could have modern significance for La Mojana, which continues to struggle with floods and severe droughts. Modern water management has often tried to hold floodwater back with dikes. The ancient system took a different approach by moving water through the landscape.
The Caregato dike has suffered repeated breaches since 2021, causing losses for communities and damage to ecosystems. Study author Fernando Montejo Gaitán of the Colombian Institute of Anthropology and History said local communities could potentially organize sustainable water management themselves, while still receiving government resources.
Evidence of raised-field use disappears before the Spanish arrived in the 16th century, and researchers do not know why the practice ended. The findings offer a new picture of how people in La Mojana transformed a difficult wetland environment through generations of local cooperation.
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