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Why did Mesopotamian farmers build irrigation canals?

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Map showing the Tigris and Euphrates river basin and its drainage network across Turkey, Syria, and Iraq, with color shading for elevation, major dams, canals, lakes, and boundaries with neighboring countries. The green areas indicate lower elevations along the river valleys, while higher elevations are shaded in brown and orange. A small locator map in the corner shows the basin's position within the Middle East. — Tigris-Euphrates river system The Tigris and Euphrates river basin and its drainage network.

Mesopotamian farmers developed irrigation canals primarily to overcome the region's challenging environmental conditions and ensure reliable agriculture.1

The region experienced very low annual rainfall and high average temperatures, leaving the ground hard, dry, and unsuitable for plant cultivation for at least eight months of the year. Furthermore, the water supply from the Tigris and Euphrates rivers was irregular, and the rivers were prone to destructive, unpredictable flooding that could damage crops.12

By constructing a widely branching network of canals, farmers were able to divert water from the rivers to irrigate extensive areas of land. This artificial irrigation transformed the fertile alluvial soil into a productive landscape capable of supporting a large population, effectively mitigating the risk of crop failure. In northern and eastern regions, farmers specifically used deflector dams to divert moderate river floods into these canals, a method that avoided the accumulation of mud and silt often associated with large storage dams.21