An Ancient Irrigation Canal in the Pampa Tamarugal (Chile)

Southwest of Tarapacá Valley, in the Pampa Tamarugal of northern Chile, the remains of a canal were discovered running south for more than 6 km. Mapping and excavations indicated that this narrow (about 3 m) and shallow (about 0.5 m) construction was intended to divert water from the perennial Tarapacá River, combine this with occasional run-off from the mountains to the east, and irrigate a system of agricultural fields in a depression on the pampa. Several piles of rocks (cairns) and cleared lines (geoglyphs) were seen in the vicinity of the canal. The recovered pottery sherds were identified as belonging to the Pica-Charcollo tradition (800–1500 c.e.), while four radiocarbon dates from excavated wood and charcoal clustered around 1400–1600 c.e. This places the canal around the time of the colonization of the area by the Inka Empire, which made Tarapacá Valley into a regional center for mining and marine resources. The rationale behind its construction is likely a combination of the need to mitigate fluctuations in the availability of water for agriculture and the production of a larger food surplus.