The largest water management feature in Khmer history was built in the 10th century as part of a short-lived ancient capital in northern Cambodia to store water, but the system failed in its first year of operation, possibly leading to the return of the capital to Angkor.
An international team of researchers led by Dr. Ian Moffat from Flinders University in Australia used ground penetrating radar to map the surface of a buried spillway in Koh Ker to better understand why the reservoir failed during its first year of use.
The Mysterious Koh Ker Temple
The monumental complex of Koh Ker, located 90 km (55.92 miles) northeast of Angkor, remains relatively poorly understood even though it was briefly the capital in the middle of the 10th century AD under King Jayavarman IV, the only capital throughout six centuries to be established outside of the Angkor region.
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The site is located in an area of gently sloping hills and stone outcrops, far removed from the low-lying floodplains that define the Khmer heartland. While the Angkor archaeological site receives several million tourists a year, Koh Ker is largely forgotten in comparison. Some conservation work was completed at Koh Ker in the 1960s to prevent further decay, but it wasn’t renovated. Nonetheless, the temple is well-preserved.
Koh Ker temple is still well-preserved. (Andreii /Adobe Stock)
The Koh Ker temple was built with processed volcanic rock inside the structure and sandstone blocks on the outside. It has seven levels and measures 66 meters (216.54 ft.) wide and 40 meters (131.23 ft.) tall. Engravings show Hindu gods holding up the sky.
A Good King Knows How to Build
In a study published in Geoarchaeology, archaeologists explain that the 7 km (4.35 mile) long embankment was designed to capture water from the Stung Rongea river but modelling indicates it was inadequate to contain the average water flow in the catchment, putting into question the legitimacy of Khmer kings, and forcing them to re-establish their capital in Angkor.
As the researchers explain in their paper , “We argue that this design flaw contributed substantially to the failure of the reservoir’s dike, possibly during the first rainy season after construction, which may have contributed to Koh Ker’s remarkably short‐lived tenure as the political center of the Khmer Empire.”
Regional map of Koh Ker showing the location of the chute and key archaeological features. The detailed map area (top right) is shown as a white dashed box on the regional map (left). The black dashed line in the detailed map area shows the approximate area of Fig 2. The location of Koh Ker compared with Angkor, Phnom Penh, and Ho Chi Minh City is shown in the bottom right. North is up in all figures. ( Dr. Ian Moffat, Flinders University )
Returning to Angkor
"At that time, embarking on projects of civil engineering such as temple building, urban renewal, and the development of water infrastructure was central to establishing the legitimacy of Khmer kings," says Dr. Moffat. And he continues:
"It's not difficult to envisage that the failure of the embankment at Koh Ker--the largest and most ambitious infrastructure project of the era--may have had a significant impact on the prestige of the sovereign capital, and contributed to the decision to re-establish Angkor as the capital of the Khmer Empire . Our study shows that this ambitious engineering feat was always doomed to rapid failure."
Angkor Thom (which means ‘Great City’) was the last capital of the Khmer Empire. As the capital, it contained important structures such as temples, royal residences, and administrative buildings. The whole space was fortified by massive walls and surrounded a large moat, which reportedly was inhabited by crocodiles. Anyone wishing to enter the city had to cross one of Angkor Thom’s enormous causeways.
That city was founded around the later part of the 12th century AD, during the reign of Jayavarman VII, following the sacking of the previous capital – Angkor – by the Chams. An interesting aspect of the city’s design is that it was meant to be a representation of Mount Meru - a sacred mountain in Hindu, Buddhist, and Jain cosmology, that was said to be surrounded by the mountains and the ocean.
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Angkor Thom gate. ( NickMo /Adobe Stock)
Another Important Khmer City
Recently archaeologists discovered another large site in Cambodia dating to the Khmer period. The discovery of Mahendraparvata, one of the first Angkorian capital cities, was revealed in mid-October 2019. The site is located northeast of Angkor Wat and LiDAR scans suggest it’s a vast centrally planned urban area encompassing about 15.4 - 19.3 square miles (40 - 50 square kilometers).
Ashley Cowie describes the site in a previous article on Ancient Origins: “Across the city grid the scans found a series of both civic and spiritual architectural installations, for example, a series of shrines, mounds, ponds, a large water-management system of dams and a major unfinished reservoir surround an administrative center, a royal palace, and a massive state pyramid-temple.”