Models of irrigation system for Pursat basin planning

The Mekong River and the Tonle Sap Great Lake in Cambodia have vast floodplain suitable for rice-based farming system. The Tonle Sap Basin, defined as the catchments of the Tonle Sap River at its confluence with the Mekong River and other 11 main tributaries draining higher ground on all sides of the basin enclosing 44% of Cambodia’s land area. The Pursat River is one of tributaries of the Tonle Sap Great Lake. It originates at Cardamom Mountains and has very good potential for agricultural development.
In this paper, we aim at applying three models of irrigation system for basin planning: Chinit (Dam-Reservoir Irrigation), West Baray (Reservoir Irrigation) and Batheay (Shallow Reservoir Irrigation) to Pursat Basin (one of sub-basin of the Tonle Sap Great Lake).
Chinit Dam-Reservoir stores water supplied by one of tributaries of Tonle Sap Great Lake, the Chinit River, located in Kampong Thom Province. Spillway is built to pass up inundation and to release water to downstream part. The rest of water in the Dam-Reservoir is distributed to the paddy field by main canal, secondary canals and tertiary canals. This system can be put at the upstream part of the Pursat River, mountainous area.
The West Baray Irrigation system is characterized by a reservoir combined with a dike system in the floodplain of the Tonle Sap Great Lake and an irrigation system situated in Siem Reap province. The reservoir is supplied by a tributary of the Tonle Sap Great Lake, the Siem Reap River, in rainy season. The water is distributed to irrigation area in dry season. A small dike system was constructed in the Tonle Sap floodplain for retarding and storing floodwater. The stored floodwater is used as an additional water source for dry season cultivation. This system can be placed at the central plain of the Pursat Basin.
Batheay reservoir directly receives floodwater from the Mekong River. It functions as both a reservoir and a paddy field. In wet season, dike around the Batheay reservoir prevents floodwater from entering the reservoir. Rainy season rice is grown inside the reservoir. After harvesting, gates around the reservoir are opened to receive floodwater. The water is stored for cultivating dry season rice outside the reservoir. This system can be put at the downstream part of the Pursat River, floodplain area of Tonle Sap River.