The inland delta formed by the San Jorge River, the Cauca River, the Magdalena River and the Nechí River, south-west of Santa Cruz de Mompox, frequently flooded during the rainy season in the mountains from April to November, causing great inconvenience to the residents of the plains. Therefore, from 200 BCE onwards these people built a system of channels that enabled them to control the flooding and make large areas practical for habitation and agriculture. The system was expanded continually. Covering 500,000 hectares between 200 BCE and 1000 CE, it was at its greatest extent in the San Jorge basin, but channels were also constructed in the lower reaches of the rivers Cauca and Sinú.40
The Zenú dug channels, sometimes as long as four kilometers, connected to the natural waterways. Perpendicular to these channels, smaller irrigation ditches were dug. The soil left by the excavations was used to build long artificial terraces, two to four meters high, on which they built their houses. During times of high water, the channels led the water to areas where crops were grown. When the water withdrew, the nutrient-rich sludge was used to enrich the land. This system of water management was used over a period of 1300 years.
40 Bowen, W. A.; Parsons, J. J. , 1966
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