Huayuri

The desert coasts of southern Peru and northern Chile are extremely dry. Nazca, the nearest sizeable city to Huayuri, receives less than 25 millimetres (0.98 in) of precipitation annually^[8] and the region is nearly devoid of vegetation, except in river valleys and where irrigation is possible. Archaeologists, however, have found evidence that the climate was less arid in the Late Intermediate Period in which Huayuri flourished.^[9]

Geoarchaeological evidence points to a climate of the Huayari region during the Late Intermediate Period, with annual precipitation between 100 millimetres (3.9 in) to 200 millimetres (7.9 in). The higher precipitation permitted rainfall harvesting at Huayuri. For rainfall harvesting to be practical, there must be rainfall—which in later centuries is almost totally absent at Huayuri—and it must be fairly reliable. At Huayuri, a substantial infrastructure for harvesting rainfall is present. The water harvesting system at Huayuri was similar to the Khadin System used in the Thar Desert of India, as well as other locations around the world in dryland areas. The catchment area for water was the rocky upland around the settled area. Terraces were built into the hillsides and captured some rainfall. Additional water was captured and directed through channels and irrigation canals downhill onto a valley plain, enclosed at its bottom end by a bund or low dam. The captured water, its downhill path blocked by the bund, sank into the soil. Crops were planted in the area behind the bund without any additional irrigation. The soil was fertile because it was constantly renewed as the water deposited sediment and at the same time washed away harmful salts. Above and below the bund, rock-lined cisterns captured and preserved water which percolated down through the soil and was used for drinking and domestic use.^[10][11]

The importance of rainfall harvesting at Huayuri indicates climate change in the Peruvian desert and that the Late Intermediate Period received greater precipitation than the historic era after the Spanish conquest beginning in 1532. However, rainfall harvesting could not create enough agricultural land to sustain a large population. The catchment area for rainfall harvesting is 15 to 25 times larger than the land that can be rendered suitable for agricultural areas. Rainfall harvesting provided only 2.5 hectares (6.2 acres) of agricultural land, plus drinking water, to the inhabitants of Huayuri. Assuming that the population of Huayuri was as large as the extensive ruins indicate, most of the food for the population came from irrigated agriculture in the adjacent valley of the Santa Clara River or was imported from elsewhere.^[12]

Huayuri reached its maximum population from 1150 CE to 1450 CE. Archaeological evidence indicates that rainfall harvesting began at Huayuri between 1260 and 1290 CE and became impractical in the 16th century, when the aridity of the region intensified and rainfall became extremely rare.^[12] Huayuri came under the influence or control of the Inca Empire in the 1470s and possibly was still occupied when the Spanish conquest of Peru began.^[13] Epidemics of European diseases, beginning in the 1520s and killing a large percentage of the Indigenous people of Peru, may have contributed to the abandonment of the site.^[14]