The collapse of a reservoir in a remote and mysterious city could have helped Angkor gain supremacy.
The empire controlled much of mainland Southeast Asia by the beginning of the 10th century A.D., but unclear rules of succession combined with a complicated web of royal family intermarriages led to a crisis. Jayavarman IV, a grandson of a previous king, contested the rule of the leaders in Angkor, the traditional seat of power. In the 920s, he set up a new capital at Koh Ker, about 75 miles to the northeast. Koh Ker flourished until 944 when Jayavarman IV’s son and successor was killed, and the next Khmer king moved the capital back to Angkor.
“It’s a very interesting period in Angkorian history where it looks like you’ve got serious competition for rulership,” says Miriam Stark, director of the Center for Southeast Asian Studies at the University of Hawai’i at Mānoa.
Without this turmoil at the new capital and a move back to Angkor, the grand treasures of Southeast Asia—such as the astounding Angkor Wat and jungle-eaten Ta Prohm—may never have been built in subsequent centuries. Now, a new study published recently in the journal Geoarchaeology shows that there was more than political intrigue at play. A water reservoir critical for large-scale agriculture in the Koh Ker area collapsed around the time the capital moved back to Angkor.
“It provides clues as to what’s going on in the empire during that time,” says Sarah Klassen, director of the Koh Ker Archaeological Project, and a post-doctoral researcher at the University of British Columbia in Vancouver, Canada.
After the Flood
Compared to widely studied societies such as the ancient Egyptians or the Maya, relatively little is known about the Khmer Empire. What scholars have learned about the royal lineage of the empire, which lasted from the beginning of the 9th century A.D. to the empire’s gradual decline starting in the 14th century, mostly comes from inscriptions on temple structures. In recent years, archaeologists like Klassen have begun using new techniques and technologies to learn more about this powerful kingdom.
Klassen and her colleagues completed LiDAR (light detection and ranging) surveys in 2012 at both Koh Ker and Angkor to map aboveground ruins, including an area near a large Khmer reservoir where a chute would have let excess water discharge downstream towards a river. Archaeologists had previously identified a dike and saw that it had broken down at some point. In 2015, they excavated part of this chute area, then returned in 2016 with ground-penetrating radar, which showed that the blocks built to limit the outflow of water had eroded.