Water Management For Agricultural Production In A Coastal Province Of The Mekong River Delta Under Sea-Level Rise

Bac Lieu province, a low-lying coastal province in the Ca Mau peninsula of the Mekong River Delta (MRD) of Vietnam, is recognized as an area strongly affected by sea-level rise (SLR) accompanying global climate change. SLR will aggravate inundation and salinity intrusion and hence exert a strong influence on agriculture and aquaculture production in the province. The study presented in this chapter aims to quantify the impacts of SLR on agriculture in this province and to propose adaptive options.The 'Vietnam River Systems and Plains' (VRSAP) model was used for simulation of water level, flow and salinity in the canal network of the MRD for 3 years of low, average and high water volume from upstream of the MRD and different levels of SLR (12, 17, 30, 50 and 75 cm). Under present sea level conditions, the western part of the province faces the highest flooding risk in October during the rainy season. In the dry season, salinity is high in the western part where farmers grow brackish water shrimp, while it is low in the eastern part where rice is grown. The inundation depth increases with the level of the SLR. For SLR less than 30 cm, salinity is expected to decrease slightly due to more fresh water from the Bassac River. When SLR is higher than 30 cm, salinity in the eastern part will also increase because the saline water intrudes into freshwater intake canals along the Bassac River. In the near future, adjustment of the cropping calendar as well as the operations of existing water control structures will be required. In the distant future, additional structures will be needed to cope with aggravated inundation and salinity.