Sancho, Pedro. An Account of the Conquest of Peru. Translated by Philip A. Means. Boston: Milford
House, 1972.
Titu Cusi Yupanqui, Diego de Castro. History of How the Spaniards Arrived in Peru. Translated by
Catherine Julien. Indianapolis: Hackett Publishing Company, 2006 [1570].
Zárate, Agustín de. The Discovery and Conquest of Peru. Baltimore, MD: Penguin Books, 1968.
■SUSAN ELIZABETH RAMÍREZIRRIGATION
Irrigation brings water to fields from a source other than rainfall. It is used when
natural rainfall is too scarce or irregular to depend on or where greater yields are
desired. The Incas made extensive use of irrigation largely to increase harvests;
the surplus supported the state and the religion. Irrigation technology predates
the Incas by several millennia, and so by the time the Incas emerged as a distinct
culture in the Cuzco valley, irrigation was widespread throughout the Andes.
Irrigation systems in the Inca Empire ranged from small, local community-
sponsored systems, to vast valley-wide ones along the north coast of Peru co-
opted by the Incas when they conquered the region.
At its simplest, irrigation involves cutting a channel for water to flow from a
source of water to the fields. In practice, it includes careful analysis of several
factors: the kinds of crops to be watered, the slope of the canal, the length of the
canal, and the characteristics of the canal (such as shape, whether it is paved or
merely lined with soil or clay, etc.).
Sources of irrigation water along the coast rely exclusively on the rivers that
tumble down the western flanks of the Andes. Many of these rivers have water
only a few months of the year, when rains fall in the adjacent highlands. Thus,
irrigation was critically important to distribute the limited water to as many
people and their fields as possible. Due to the relatively flat topography of the
coastal plain, primary canals could be tens of kilometers long, with secondary,
tertiary, and quaternary canals dividing the water for field systems. Due to
evaporation and loss of water through the unpaved canals, as much as 85 percent
of the water was lost before it reached its destination. The distribution of water
was a major concern for polities that formed in these valleys, and for the Incas as
well.
Because of the extreme aridity of the coastal zones of Peru and Chile under
Inca control, irrigation was a requirement. Societies along the north coast of Peru
were among the largest of those conquered by the Incas, and their large-scale
irrigation systems were one major reason for their success. The Chimú Empire,
for instance, boasted three major canals that delivered water to fields throughout