The Land

Lying completely within the tropics, and north of the Equator, mainland Southeast Asia is subject to a strongly pronounced monsoon cycle: a season of heavy rains that

¹ Sinopoli 1995, 160.

Michael D. Coe, The Khmer Empire In: The Oxford World History ofEmpire. Edited by: Peter Fibiger Bang, C.A. Bayly, Walter Scheidel, Oxford University Press (2021). © Oxford University Press. DOI: 10.1093/oso/9780197532768.003.0015. runs from late May and June through the middle of November, followed by a dry season from late November until the monsoon rains begin anew. The rice farming, on which nearly all inhabitants of this vast area depend, and the freshwater fish re­sources of the rivers are tied to this annual climatic pulse. However, the arrival of the rains is by no means a certainty, for there are occasional years in which droughts— sometimes severe—may occur, with devastating results. As we shall see, this was a phenomenon that the Khmer rulers strove to overcome by great public works.

This is a land of rivers, the most important of which is the Mekong, Asia' s longest waterway (see Map 15.1). Originating in the Tibetan highlands, the Mekong flows through southern China, touches upon Burma, passes between Laos and northeast Thailand, and crosses Cambodia to empty through myriad branches in the Delta of

Map 15.1. The Khmer Empire under Jayavarman VII.

Source: Coe, 2003, Angkor and the Khmer Civilization, figure 63. Copyright: Michael D. Coe.

Vietnam. The Mekong is virtually a lifeline for the Khmer, and its annual cycle of flooding then falling continues to have strong effects on their livelihood.

Modern Cambodia is a lowland tropical basin. Within it is the Tonle Sap, the lar­gest lake in Southeast Asia. Because it is very shallow, and connects to the Mekong by its own river, the Tonle Sap's size varies with the larger river's annual pulse.

The Khorat Plateau of northeast Thailand was once an important part of the em­pire, and is divided from Cambodia by the Dangrek range, which really forms an escarpment looking south over the Cambodian basin. Because of Khorat's rela­tive aridity, wet rice agriculture is severely limited, the most productive land being the valley of the Mun River, which is a tributary of the Mekong. Today, Khorat is Thailand's poorest province.

Beyond Cambodia's present-day western limits lies the Chao Praya river system, which drains most of modern Thailand to the west of Khorat Plateau. Subject like the Mekong to annual flooding—which might be very severe in some years—it nev­ertheless supports very productive wet rice farming. Until the invasion of the Thai dislodged it, the Khmer state had incorporated all of this region into their empire.