At one point 1200 kilometers of stone canals provided water to 330 km² of cultivated land in the Tehuacán Valley.
The Tehuacán Valley is rich with mineral springs, and these water sources were eagerly tapped for farming by early residents of the area.
As the water ran through the canals, calcite was slowly but steadily deposited on their walls, forming a hard, stony layer.
Through concentration and evaporation calcite crystallized on the earthen surface of the canals, forming a leakproof shell of travertine.
This material yields information about the composition of the water, the flow rate in the aqueducts, and the wild and cultivated flora of the area.
Also, biological material trapped in the stone can be used for radiocarbon dating of the canals; the first ones were dug as early as 800 BC, and water ran through them as recently as the sixteenth century AD.