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The technology for harvesting water that enabled the Khmer to
thrive also led to their fall, researchers say.
The ancient Khmer city of Angkor in Cambodia was the largest
preindustrial metropolis in the world, with a population near 1
million and an urban sprawl that stretched over an area similar to
modern-day Los Angeles, researchers reported Monday.
The city's spread over an area of more than 1,350 square miles
was made possible by a sophisticated technology for managing and
harvesting water for use during the dry season -- including
diverting a major river through the heart of the city.
But that reliance on water led to the city's collapse in the
1500s as overpopulation and deforestation filled the canals with
sediment, overwhelming the city's ability to maintain the system,
according to the report in the Proceedings of the National Academy
of Sciences.
The hydraulic system became "not manageable, no matter how many
resources were thrown at it," said archeologist Damian Evans of the
University of Sydney in Australia, the lead author of the
paper.
But during the six centuries that the city thrived, it was
unparalleled, particularly because it was one of the very few
civilizations that sprang up in a tropical setting, said
archeologist Vernon L. Scarborough of the University of Cincinnati,
who was not involved in the research.
Just one section of the city, called West Baray, was many times
"larger than the entire 9-square-kilometer hillock on which sat
Tikal, the largest city in Central America," he said.
"The scale is truly unparalleled," added archeologist William A.
Saturno of Boston University, who also was not involved.
"Forest environments are not good ones for civilizations . . .
because they require intensively manipulating the environment," he
said. "Angkor is the epitome of this, and it is going to be the
model for how tropical civilizations are interpreted."
Old and new technologies The new data come from an unusual
agglomeration of both old and new technologies. The core data came
from a synthetic aperture radar unit flown on the space shuttle in
2000 and managed by NASA's Jet Propulsion Laboratory in La
Cañada Flintridge.
The radar pierced low-lying clouds and vegetation to give an
accurate picture of soil density, local structures and moisture in
soil, which reflects growing conditions.
The images revealed, for example, the characteristic
moat-enclosed local temples and artificial ponds used for water
storage and irrigation.
This information was supplemented with photographs taken from
ultralight aircraft flown over the city at low speeds and
altitudes.
Finally, the researchers used motor scooters to traverse the
city and closely examine sites revealed on the radar images. But so
many sites have been revealed, Evans said, that the researchers are
only partway through this process.
The group, collectively called the Greater Angkor Project,
released a partial map three years ago. The new one released Monday
contains, among other things, an additional 386 square miles of
urban area, at least 74 long-lost temples and more than 1,000 newly
recognized artificial ponds.
Angkor was the capital of the Khmer Empire, which got its start
in AD 802 when the god-king Jayavarman II declared the region's
independence from Java. At its height, the empire covered not only
Cambodia but also parts of modern-day Laos, Thailand and
Vietnam.
It is perhaps best known for Angkor Wat, the magnificent temple
built by King Suryavarman II in the early 12th century.
Angkor has been studied for more than a century, but early
scholars were so overwhelmed by the artworks and architecture, as
well as the political successions, that they ignored the
archeology, said coauthor Roland Fletcher of the University of
Sydney.
In the late 1960s, French archeologist Bernard-Philippe Groslier
began a more formal study of the ruins, but that work was halted
for more than 20 years by the war that broke out in 1970.
After the war, archeologist Christophe Pottier of the Ecole
Francaise d'Extreme-Orient in Siem Reap, another coauthor, renewed
the work, beginning what eventually grew into the current
project.
Disputes over history In the process, the researchers have begun
solving many of the disputes that have arisen over the city's
history, Evans said.
"The debate has always been . . . was it large enough, was the
manipulation of the landscape intensive enough to cause
environmental problems?" Evans said. "The answer is definitively
yes."
Other arguments have been based on the assumption that Khmer
hydraulic engineering technology was rather rudimentary, he said.
"What our research has shown is that it was extremely sophisticated
and highly complex," he said.
Many of the reservoirs and walls of canals were constructed of
compacted earth, he said, but junctions and other crucial points in
the system were "quite sophisticated stone structures."
The Khmer built, for example, a massive stone structure to
divert the Siem Reap River from its old bed through the center of
the city. Other sites have stone structures built into the walls to
manage the inflow and outflow of water, he said.
The system was complex enough that the Khmer could have grown
rice throughout the year and not just during the rainy season,
Evans said. It is not yet clear if they did so, however.
"The intentional movement of earth to create the whole water
system is just really mind-boggling," Saturno said. "It was an
enormous undertaking" that required not just administrative skills,
but also engineering know-how and massive amounts of physical
labor.
But in the end, maintenance became too labor-intensive, Evans
said. As trees were removed from the landscape, sediment began
accumulating in the canals at a rate more rapid than it could be
removed. Many dike walls collapsed, although it is not yet known
when that occurred.
"We're going now and excavating [the sites] on the ground, and
trying to get a grip on when they happened -- whether they were a
precursor of the decline, a symptom or the system gradually falling
into ruin after they left," he said.
Source: LA
Times
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