SIX CENTURIES OF HYDROLOGICAL DIVERSION AND ARTIFICIAL OASIS IN THE PERUVIAN DESERT: THE PRE-HISPANIC RACARUMI INTERVALLEY CANAL SYSTEM

The Racarumi Canal Intervalley Canal System (RICS) in north coastal Peru was constructed by the Sican ~ AD 1000 and maintained until Spanish conquest. The purpose of the RICS was to expand agricultural production through the diversion of water from the Rio Chancay over a low topographic divide northward into the Pampa de Chaparrí, a tributary basin of the Rio Leche. Up to approximately half of the Rio Chancay discharge was diverted into the normally dry pampa creating an artificial agricultural oasis and reducing the amount of water available for downstream canal systems. Several hundred kilometers of canals were cut across the landscape, and ~ 5600 ha of former agricultural fields are still visible at the surface. Surficial geological mapping and excavations of distribution canal segments provide insight into the operational history of the RICS and the impacts of El Niño flooding. AMS-¹⁴C (n=8) and single grain infrared-stimulated luminescence (IRSL) dates (n=12) from canal deposits confirm operation of the system despite recurrent El Niño flood damage and conquests by the Chimu (~ AD 1350-1400) and Inca (~ AD 1460). Some of the ¹⁴C and IRSL dates have error ranges that extend into the 1600s suggesting the RICS may have continued to operate for some time after arrival of the Spanish. The RICS and other pre-Hispanic intervalley canal systems in coastal Peru involved large amounts of human labor that created artificial oases for increased agricultural production in support of temporary political states. They are prehistoric analogs for modern major water infrastructure projects.