RAISED-BED IRRIGATION AT TIWANAKU, BOLIVIA
RAISED-BED IRRIGATION AT TIWANAKU, BOLIVIA
The Bolivian Altiplano is a high-elevation (over 12,000 feet above
sea level), seemingly inhospitable environment. At first glance, it appears
an unlikely locale for a flourishing empire capable of supporting a large
population. Yet for approximately 600 years, the Tiwanaku Empire thrived on
The Empire rose about 400 AD, fed by local abundance - fish from the lake
Titicaca (the world's highest navigable lake), meat from llamas and alpacas
pastured on high plateaus, and potatoes and other crops grown in raised-bed
fields fed by irrigation channels and drained by massive ditches.
Like other empires, Tiwanaku's
expansion depended on abundant food production, and for over seven centuries,
it regularly produced food surpluses. These surpluses were a product of
ingenious irrigation systems.
According to Andean religion the creator emerged from Lake Titicaca
to shape the earth and the first people. Because of its sacred nature, the
lake's shores are ringed with the ruins of small shrines and temples, some
dating as far back as 700 BC. Researchers think that Tiwanaku (the city)
was originally one of these small religious centers.
Tiwanaku, the Community
But in the 6th century, because of the political
power of the Tiwanaku people, Tiwanaku became a prize pilgrimage center.
Many of these pilgrims traveled long distances, crossing the Titicaca's blue
waters on reed crafts. Then they walked due east over the grassy plains of
the altiplano toward the blue-and-white peaks of the Andes
(see Illustration 2).
For most of the journey, Mt. Illimani was a beacon. Illimani was their
most sacred mountain, where they believed many of their ancestors went when
they died. When pilgrims arrived at Tiwanaku, Illimani was before them and
Lake Titicaca behind them. The site must have had a strong emotional impact
(which was enhanced by drugs), a place between heaven and earth.
Tiwanaku, besides being an large city, contained several large temples
which were surrounded by a moat, creating a miniature lake with the temple complex as
as island. The central temple, called the Akapana, was constructed in a series
of seven tiers, to resemble the nearby peaks. Tiwanaku engineers
plumbed the Akapana with drains so that when the
annual rains arrived, water would thunder through it. "It was a way of
renewing the earth and maintaining the circulatory system of the universe,"
says Alan Kolata, a University of Chicago archaeologist, who thinks the
Tiwanaka probably celebrated fertility ceremonies and other rites while
water roared through their mountain-temple (see Photograph
At their peak between 700 AD and 1000 AD, the Tiwanaku Empire controlled nearly
entire Lake Titicaca basin as well as extensive holdings in Peru and Chile.
Their engineers and farmers turned the broad valley of the
Katari River, a tributary of Titicaca, into their breadbasket, using extensive
canals and causeways to irrigate a vast area of corn, potatoes, quinoa,
and other crops. "They actually altered the meanders of the river," says John
Janusek, an archaeologist at Vanderbilt University who excavated several
Tiwanaku settlements, "and turned it into a straight shot through the valley."
A 32-year drought from 563-594 AD caused widespread devastation across
empire. There is evidence, however, that a lesson was learned. The rulers
took the catastrophe as a warning. They revolutionized their agriculture,
instituting a totally new system which, some believe, allowed the empire to
prosper for an additional 400 years. In any event, Tiwanaku agricultural surpluses
after the drought can be attributed to raised-bed irrigation. Water surrounded
raised agricultural mounds (see Photograph
Warmed during the day, the water kept the crops from freezing during the
cold Andean nights and even extended the growing season. Raised-bed agriculture
grew to encompass an immense area, at least 19,000 hectares (47,120 acres).
Studies show that land cultivated in this manner could yield 20 metric tons
of potatoes per hectare. Construction of the raised-bed irrigation system no
doubt required major earth moving operations.
Fall of the Empire
The German adventurer Arthur Posnansky explored Tiwanaku in 1904
and, his 1945 monumental two-volume book attributed its decline to "malign
climate conditions." Indeed, the historical record confirms that Andean
climate can be malign.
Climatological data developed by
Lonnie Thompson from the
Quelccaya Ice Cap in Peru indicates a decrease in precipitation between 650
AD and 730 and between 1245-1310. High dust concentrations peaked between
600-920 coinciding with periods of massive field construction. Also
beginning in 1000 there was a rise in the mean temperature (between
0.5 and 1 degree). Kolota suggests that this is the beginning of the
Little Ice Age, which caused a serious drought resulting in agricultural
collapse and ultimately the demise of the Empire.
Kolata's version of the decline and fall of the Tiwanaku Empire, however,
is not the only one. Another theory holds that the demise resulted from a
fracturing of the belief structure and trade systems, starting at the
periphery and culminating in the abandonment of the pilgrimage center at
Tiwanaku. But even if you buy the latter argument, its hard to dismiss the
evidence of environmental determinism.
Morell, Virginia, 2002, "Empires Across the Andes," National Geographic,
June, pp. 123-128.
Wright, Kenneth R., 1998, "The Lessons of History: El Nino and the
Fall of Empires," Quarterly Journal of the South American Explorers Club,
August (Number 53), pp. 22-23.