Photo courtesy of Cambodia Tourism Commission

Can Angkor Wat Teach Us About Water Management?
| Published May 4, 2014 |

By Earl Perkins
Thursday Review associate editor

Man has experienced problems with water management systems dating to Ancient Rome and beyond, but archaeologists say those issues may have also driven residents from Cambodia's famed Angkor Wat temple complex 1,200 years ago.

Airborne laser technology (lidar) uncovered roadways and canals, producing a detailed map of a vast cityscape which reveals a bustling ancient city linking the complex, according to a peer-reviewed paper released by Proceedings of the National Academy of Sciences journal in June 2013.

Angkor Wat is Cambodia's top tourist destination and one of Asia's most spectacular landmarks, constructed in the 12th century during the Khmer Empire. Cambodians are extremely proud of the temple, placing it on their national flag and having it named a UNESCO World Heritage Site.

Those high tech airborne lasers show numerous highways and previously undiscovered temples in the city known as Mahendraparvata, which archaeologists had suspected lay beneath a canopy of dense vegetation. The site is located on present-day Phnom Kulen mountain in Siem Reap Province.

"No one had ever mapped the city in any kind of detail before, and so it was a real revelation to see the city revealed in such clarity," said Damian Evans, University of Sydney archaeologist and the study's lead author. "It's really remarkable to see these traces of human activity still inscribed into the forest floor many, many centuries after the city ceased to function and was overgrown."

Researchers loaded equipment onto a helicopter in April 2012, spending days crisscrossing the forest from 2,600 feet. In 20 hours of flight time, they covered 370 square miles of terrain, studying Angkor and the two nearby complexes of Phnom Kulen and Koh Ker. Their findings were later confirmed by Australian and French archaeologists who slogged through the thick vegetation on foot. Researchers had previously spent years doing ground research and excavations mapping a 3.5-square-mile section, but the lidar revealed a 14-square-mile downtown which had a larger population than previous estimations.

"The real revelation is to find that the downtown area is densely inhabited, formally-planned and bigger than previously thought," Evans said. "To see the extent of things we missed before has completely changed our understanding of how these cities were structured."

Archaeologists are unsure exactly why Mahendraparvata's civilization collapsed, but some theorized water management issues may have driven out residents, he said.

Researchers are anxious to begin excavating the site in the near future, seeking clues concerning those who lived there. They will recover and analyze material and environmental data left behind, including artifacts, architecture, biofacts (eco-facts) and cultural landscapes.

The medieval Khmer Empire traces its origin to Jayavarman II, who proclaimed himself King of the World in 802 CE. History shows the great ruler may have jumped the gun slightly, noting several centuries passed before the Khmers eventually built Earth's largest religious monument. Angkor Wat became the crowning glory of a kingdom that by the 13th century spanned an area of approximately 1,000 square kilometers, located today in northwestern Cambodia. The vast urban landscape is hidden in Kulen's jungle and in lowlands surrounding the temple.

The laser imaging reveals a cityscape at the heart of the Khmer Empire (9th to 15th centuries CE) that was more sprawling and complex than previously thought, leading archaeologists to consider the possibility that climate change and the kingdom's sprawling waterworks made the complex unlivable.
Angkor was considered to be the most extensive city of its type in the pre-industrial world, with its waterways and reservoirs vital to produce enough rice to sustain hundreds of thousands of inhabitants. At its height, the empire covered much of modern-day Cambodia, central Thailand and southern Vietnam, and the lidar information “is astonishing,” according to Roland Fletcher, a university of Sydney archaeologist and member of the international team. "We found the great early capital of the Khmer Empire," he said.

Their research in recent years shows Angkor's waterworks began breaking down as the kingdom faded into history, which can probably be traced to decades-long mega-monsoons and droughts in 14th century Southeast Asia (according to 2009 tree ring data), Fletcher said. “Things are going wrong by the 1300s." Massive sand deposits in canals and spillway ruins the Khmers may have ripped apart were red flags for researchers, he said.

“The discovery of this early Angkorian city is a very exciting example of lidar’s use in the region,” adds Miriam Stark, an anthropologist at the University of Hawaii, Manoa, who has recently started conducting research at Angkor but wasn't involved in last year’s investigation.

The lidar research shows medieval settlements at Phnom Kulen and Koh Ker had extensive hydraulic engineering on a scale comparable to Angkor, showing a much wider reliance on water management systems “to ameliorate annual-scale variation in monsoon rains and ensure food security,” the team reports. Some readings uncovered cryptic coil-shaped rectilinear embankments covering several hectares near Angkor.

“It was an unbelievable surprise,” Fletcher said. “Nothing like them had been seen before in Khmer architecture.” They may have had some role in farming, but the team cannot say for sure what their function was. Also the lidar data showed "very serious" erosion in parts of the ancient city, accounting for deep sand deposits found in excavations, Fletcher said.

The UNESCO website describes Angkor and its wider footprint "as one of the most important archaeological sites in Southeast Asia." UNESCO is seeking to establish a comprehensive program to balance the vast historical importance and cultural significance of the huge site with the always-increasing pressures of tourism. Some UNESCO representatives are concerned that the nearby development of large hotels, huge restaurants, shops and other tourism-related construction could disrupt the water suppply and the water table, eventually causing severe structural damage to the ancient site. According to the British news site, The Independent, Angkor Wat receives over 3000 visitors in a typical day, making it one of the world's busiest tourist attractions.