Phnom Penh/ “Prek” – How Mekong River was shaped
One of the earliest Khmer ways of managing water is perhaps the “prek”.
“Preks” are characteristic of Khmer settlements, and are still existent in many areas today. They were simple but effective attempts in managing the annual flood cycle in order to make the rise in water level beneficial to production. One can say that the “prek” is a canal through which water runs into the fields in times of flooding and then back into the river during the dry season. The bottom of the “prek” is somewhat higher than the water level of the river when it is at its lowest, so that the first flood waters do not pass through the “prek”. Eventually as silt-laden waters emerge, they pass through the “prek”, flooding the interior fields. As a result, new silt is deposited in the low-lying fields behind the “prek”, and such land is resulted as the most fertile in the country.
The use of floodwaters does not end here though. As the flood waters recede, some of them is stored in ponds known as “beng” found in the low-lying fields beyond the river bank. The water deposit in beng is eventually used and dried up as dry season kicks in, only to become large lakes again when annual rains return and flood waters come.
The building of such water systems is mostly through collective labor organized by notables and elders in the community back then. Although primitive, the hand-dug system has allowed flood waters to fill the low-lying fields behind the natural embankments of the river banks, making most out of floods that come annually. This has been one of the main determinants to the morphology of the Mekong River over the years.
Referece: Modern Khmer Cities, Vann Molyvann (2003)