The ancient city of Angkor, Cambodia (of the Khmer culture) covered more than 160 km2 in northern Cambodia, situated on the edge of the Great Lake (Tonle Sap). The Classic Angkor civilization was part of the Khmer culture (between A. D. 802 and 1327). Prior to A. D. 802 the Khmer political landscape consisted of a number of independent kingdoms (Coe, 2003). Angkor became the imperial capital of the Khmer Empire. Ancient Angkor was a vast complex of temples built from the 8th to the 13th centuries A. D. Figure 11.6 Is map of Angkor showing surface features such as topography and waterways. A study by Evans et al. (2007) concluded that the area of Angkor’s urban complex was roughly 900-1,100 km2 which is almost four times the size of present day New York City. Angkor was a low density city with dwellings and water tanks spread over the area and connected by roads.
Angkor is located in the Lower Mekong Basin which is subject to an annual cycle of monsoons causing alternation between a wet rainy season (summer monsoon) and a strongly marked dry season. The heavy rainfall during the summer monsoon causes the Mekong River and its tributaries to rise and flood low-lying areas. Snow melt in Southwestern China and Tibet flowing down the Mekong contribute to the flood volume. The Tonle Sap River, a tributary of the Mekong, reverses flow because of the back water effects from the large flows in the Delta of the Mekong and causes the water levels in the Great Lake (Tonle Sap) to rise. Floods subside during the
Fig. 11.6 This is a map derived from airborne data sources and earlier archaeological maps. Source: Http://earthobservatory. nasa. gov (courtesy of NASA)
Winter monsoon and again river flow is toward the Delta causing the water levels in the Great Lake (Tonle Sap) to lower. Total rainfall in the Lower Mekong Basin fluctuates from year to year and is never very high, with an average of 150 cm per year in area of Angkor. In Phnom Penh the mean rainfall is 143 cm and can be as high as 231 cm and as low as 97 cm.
Angkor Wat, a temple complex, is surrounded by a 200 m wide moat (see Fig. 11.7) that measures approximately 1,500 m on each side (a square of approximately 21 ha) and a laterite wall (Coe, 2003). To the north of Angkor Wat is Angkor Thom (Great Angkor), another larger temple complex and location of the Royal Palace, which was a large square 3 km on each side with an area. Angkor is also surrounded with a moat (see Fig. 11.7) and a laterite wall.
The ability to store water was accomplished by constructing large reservoirs called barays. These reservoirs had inlet and outlet control structures so that they were used both in the time of drought and flooding. There were four large barays which had the respective approximate storage volumes (Coe, 2003): West Baray (48 million m3), East Baray (37.2 million m3), Jayatataka Baray (8.7 million m3), and Indratataka Baray (7.5 million m3). The approximate surface areas of these barays are West Baray (16 million m2), East Baray (12.4 million m2), Jayatataka Baray (2.9 million m2), and Indratataka bay (2.5 million m2). The West Baray even holds water today. All of these barays may not have been functional at the same time, but one thing is for certain the water management system including the borays and other water infrastructure such as moats, canals, etc. required constant maintenance. A vast canal system was built that was used for both irrigation and transportation.
Fig. 11.7 Angkor Wat illustrating the moat surrounding the temple complex (courtesy of NASA)
Angkor was an agrarian state which had rice production as its basic foundation for the classic Khmer civilization; therefore, it would make sense that the most likely purpose of the barays was for providing irrigation water. Borays were built to store water above ground, and were constructed using elevated, earthen dikes. They most likely had other uses such as flood control, recreation, worshiping, and others. In fact Bernard-Philippe Groslier (1979) viewed Angkor as a “hydraulic city”. Based upon his calculations the hydraulic system might have supported 600,000 inhabitants. In addition he considered an estimated 429,000 persons that would have been fed by flood-retreat agriculture and another 872,000 people supported by dry rice farming. This would approximate Angkor as having around 1.9 million inhabitants, certainly a mega city of the time. Others such as Acker (1998) concluded that only a small percentage of Grosslier’s estimate could have been supported. However, a more recent study by Evans et al. (2007) added to the Groslier’s conclusion of Angkor being a hydraulic city built for irrigation to counter the unpredictable monsoons. This study also has confirmed that the Angkor site was the largest pre-industrial city known so far. It was several times the size of Tikal, the Mayan city in Belize.
Early in the 15th century A. D., the Khmer empire basically had ceased to exit. Several theories have evolved as to the downfall of the classic Khmer civilization of Angkor. Grosslier advocated that Angkor fell mainly because of the decline and eventual abandonment of the massive water-management system. He argued that
As the system declined it was neglected and filled with silt. Through the use of radar images it has become apparent that rice fields extended from the relatively flat lands of Angkor north to the foothills as a result of increasing population pressure. The lower slopes (Kulen Hills) of the forest cover were logged to clear for cultivation, and also for timber and firewood. This deforestation exposed the complex system of barays and canals to both extensive siltation and flooding and erosion. Probably the barays and canals allowed two annual rice harvests by irrigation and one crop-a-year by flood-retreat farming along the Great Lake. Evans et al. (2007) suggested causes for the failure of Angkor because of the attempt to overcome nature through engineered changes. Deforestation, degradation of topsoil, and erosion, combined with water management operation problems, breaches and failures within the management system contributed significantly to Angkor’s failure.
Here is an example of an ancient mega city failing as a result of poor water management practices. The classic Khmer civilization must not have lived in harmony with nature.
World History
