Because the Hohokam had no draft animals, they carved the canals by hand using hafted stone hoes. With these simple tools, they created a precise downhill gradient of 0.3 to 0.5m every 1.6km. At the heart of the system, the Salt River, the channels started out large – more than 25m wide in some places. Then they slimmed as they branched into lateral canals and furrows, like watery arteries and capillaries writ large. These design features helped keep the flow at a consistent rate while minimising siltation and erosion.
