THE MEKONG DELTA is famous as the hearth of one of the earliest civilizations in mainland Southeast Asia. Called "Funan" by visiting Chinese dignitaries, the lower Mekong Delta housed at least two urban centers by the third century A.D.: Oc Eo in current-day Viet Nam and Angkor Borei in Cambodia (Coedes 1931; Jacques 1979; Mabbett and Chandler 1995). Brief examination of Oc Eo in the early 1940s (Malleret 1959-1963) revealed a complex system of water control, monumental architecture, and a rich material culture. Little is known about the subsistence or economic basis of the Funan civilization, and its location in the Mekong Delta poses a paradox for understanding human colonization of the area. The delta is an uncomfortable environment for human survival. Today's inhabitants are forced to live in their houses and on their boats for four to five months a year when the river floods; natural vegetation, including both freshwater mangroves and riverine forests, is dense and difficult to control; and drinking water is scarce in the dry season. Yet this same environment is also exceedingly fertile because of the annual deposition of silt laid down by the retreating floods.
This paper describes current land-use practices in and around Angkor Borei, as well as practices found in the recent past, and hypothesizes on the relative antiquity of these practices with respect to early state formation in the region. Dry-season flood-recession rice, the major land use in the area, is an ancient land-use system that, taking advantage of the fertile silt deposited by the annual floods, is both extremely productive and sustainable. In modern times, Cambodian farmers grow dry-season flood-recession rice in areas where the maximum height of the annual flood exceeds 3 m (too deep for most rice varieties), or where the flow of water is very rapid, making it risky to plant floating rice (a variety adapted to slow, regular flooding with stalks that reach 5 m long) (Delvert 1961:331). Flood-recession farmers store floodwater in bunded areas and man-made reservoirs and then release this water to supply paddies situated below the bunded areas during the dry season. If conditions permit, farmers prefer to grow flood-recession rice, because yields are higher in comparison both with floating rice and with transplanted wet-season rice due to the enhanced fertility of the silt deposited by the floods.
The low-lying Angkor Borei basin allows the rising floodwaters of the Tonle Bassac (Bassac River) to spread out across the landscape and diminishes the impact of the flood on any one site. Thus, like its counterpart to the north, Tonle Sap (the great lake), the Angkor Borei basin is a natural mechanism for the renewal of soil fertility. We suggest that dry-season flood-recession rice was the land-use system that supported Angkor Borei and the Funan polity in the second to sixth centuries. Furthermore, we hypothesize that the system of dry-season flood-recession agriculture was adopted elsewhere in the delta either in advance of or in congruence with other lower Mekong polities (e.g., Chenla and Angkor). If this hypothesis proves true, then dry-season flood-recession rice has played a much larger role in the early history and culture of the lower Mekong Delta than has been appreciated by students of the region.
Van Liere, writing on traditional water management in the lower Mekong basin, describes the landscape morphologies and the types of rice farming that developed in response to these landscapes.
First, there is the channel or channels of the main river, with adjacent
levees or riverbank deposits. Then, behind the river banks, are the back
swamps, connected with the main channels by distributaries and acting as
natural flood regulators when the monsoon river rises rapidly. Back swamps
are very common in the lower Mekong basin. They vary greatly in size, the
largest being the Great Lake in Cambodia, which covers one million hectares
when the Mekong is in flood. …