A Water Control System

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Current view of the artificial Canals built by former Zenú people to control flooding. They change the landscape of a large region in the Colombian plains on the Caribbean.  San Marcos, Sucre.

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The Floodable Caribbean Plains

Every year, the Mompox Depression in the middle of the Caribbean Plains receives the waters of the rivers Magdalena, Cauca and San Jorge that flow down from the cordilleras. These floodwaters, which bring with them a fertile deposit of sediments, leave the area under water for eight months of the year. Nowadays, people suffer the loss of their homes and belongings, their crops and their cattle, year in year out, but in pre-Hispanic times, the Zenúes made the most of the water and silt. In a long process which was at its peak between 200 B.C. and 1000 A.D., they transformed the landscape by means of an ingenious water control system.

The waterway system, consisting of an enormous network of canals and ridges, eventually covered an area of 500,000 hectares in the San Jorge basin, and a further 150,000 around the River Sinú.

The system set out to ensure that the courses of the rivers and channels remained stable. They were surrounded by artificial islets, on which people’s homes were built. Perpendicular to these channels, the Zenúes dug canals ten metres apart and up to four kilometres long, along which the floodwater flowed to the marshes lower down. There, the current was halted by means of short, interlinked canals between 30 and 70 metres long, so that large areas where crops were grown could be created.

This way, up to 2,000 hectares were made available for agriculture, as when the water levels dropped, the canals retained humidity throughout the dry season. The nutrient-rich sediments were gathered from the canal beds and taken to the tops of the raised fields to act as fertiliser, so that crops could be planted. Some sectors were dedicated to a single crop, while in others various species were grown: coca (Erythroxylum sp.), corn (Zea mays), sweet potato (Ipomoea batata), pumpkin (Cucurbita maxima), chili (Capiscum sp.), marrow (Cucurbita mixta), cassava (Manihot esculenta) and many different fruits.

A strict, complex social and political organisation meant that the Zenúes were able to adapt the landscape and to keep the canals clean for an unbroken period of 1,300 years, thus enabling a large population to be fed without harming the environment.