How it began
The Angkor Empire dates its start to 802, when its founder Jayavarman II was consecrated with water on Phnom Kulen in present-day Cambodia. When the capital moved south to Roluos and then to Angkor, engineers built a water system to serve it. A study in the International Journal of Intangible Heritage notes that Khmer engineering of the 9th century already managed water with basins, moats and reservoirs that stored the excess. Successive kings expanded, restored and improved the network for more than five centuries.
How it works
Canals carried water from Phnom Kulen to the plains of Angkor. The network joined canals, dikes, moats and reservoirs called barays, with works to control flow. The West Baray alone measures 7.8 kilometers by 2.1 kilometers. The system held monsoon water for year-round use by people, crops and livestock. Moats also kept groundwater steady beneath the temples, because the engineers found that wet sand makes a stable foundation for heavy stone.
Who pushed back
The network became a weakness as it grew larger and more interdependent. Research shows that in the late 14th and early 15th centuries prolonged monsoon rains were followed by intense droughts. According to Dan Penny of the University of Sydney, the swings broke the network into pieces and made it unusable. Together with attacks from Siam, this contributed to the move of the capital south to Oudong.
What changed first
Water was central to the rise of the city, which became the largest urban center of the pre-industrial world. The canals were used to move an estimated 10 million sandstone blocks, weighing up to 1,500 kilograms each, to the building sites. Angkor also stood beside the Tonle Sap lake, one of the most productive inland fisheries, and on good rice soil.
What lasted
In the 1950s and 1960s the French archaeologist Bernard Philippe Groslier used aerial archaeology to map the system and called Angkor the Hydraulic City. In 2012 airborne laser scanning led by Damian Evans revealed its full extent of about 1,000 square kilometers. Penny describes the scale of the reservoirs as unique among historic cities.
Where it stands today
After floods from 2009 to 2011 and water shortages driven by tourism, the APSARA National Authority restored many barays and waterways, including the 12 kilometer moat of Angkor Thom, the West Baray and the 10th-century basin Srah Srang. The old system again supplies irrigation water to Siem Reap, limits flooding and keeps the temple foundations stable.
