Stone-faced terraces at Choquequirao in the Inca province of Vilcabamba, west of
Cuzco, not only prevented erosion, but also provided land for planting crops.
Adriana von Hagen.Some terraces were designed to receive irrigation water while others relied on
rainfall. Canal systems brought water from the upper terraces to the lower ones,
and distributed the water along the surface of the terrace.
In many regions of the Andes, a main canal brings water from a stream
flowing from permanent snowfields above the valley down to the terrace system.
From there it flows horizontally above a series of terraces; vertical drop canals
bring it down to a set of terraces. Canals along the back of each terrace have an
input off this vertical canal that can be blocked with a stone. Water is distributed
across the surface of the terrace from that canal.
Terraces do more than just provide additional planting surfaces. Terracing
deepens soils, reduces erosion, and controls moisture. It creates a
microenvironment that often mitigates frost damage because the contour terraces
cause turbulence in the cold air moving down slope. Terraces provide a deeper
soil bed for better root development than an unmodified slope. In areas where
rainfall is scarce, they also allow for irrigation. All of these factors increase
agricultural productivity.
Terracing technology long preceded Inca expansion, both in the Cuzco region
and elsewhere, but the Incas probably were responsible for a vast increase in
terracing. The Incas divided conquered peoples’ lands into three parts: those of
the Sapa Inca, the Inca religion, and the local community. Using mit’a labor,
they constructed new irrigated terrace systems that allowed for the production of
surpluses. In some regions, unirrigated terraces were augmented by the
construction of irrigated terraces below them.
Inca-constructed communities, such as the royal estates, are especially famed
for the terraces that formed part of their overall design. Machu Picchu, the most
renowned of these, includes two sets of contour terraces constructed to support
the crops of its occupants. Nevertheless, Machu Picchu’s terraces were
insufficient to feed its estimated 300 permanent residents, and food was probably
brought in from elsewhere.
Inca agricultural specialists developed an understanding of the best locations
and construction techniques to use in different regions. They used mit’a labor to
build the terrace systems, grow the crops, and create surpluses for the empire.