39 / 2023-12-25 04:04:37

DETERMINE THE TIMING OF FRESHWATER APPEARANCE IN DINHAN BRANCH OF MEKONG ESTUARIES

Salinity intrusion, Mekong estuaries, tidal regime, mixing and stratification

Vietnamese Mekong Delta (VMD) contributes over 50% of the country's total rice, 70% of fruit, and 74% of aquaculture production. In recent years, VMD has faced severe freshwater shortages at the beginning of the dry season due to the significant impacts of salinity intrusion and climate change. Field surveys and numerical modeling MIKE 1D - 3D were used to investigate salinity intrusion mechanisms to determine the timing of freshwater appearance during the dry season.

The research findings show that the peak salinity concentration (S_max) occurs at the bottom and appears after the maximum water level for 1 to 2 hours within one tidal cycle. While in the fortnight cycle, S_max occurs during the transition period from neap tide to spring tide. Furthermore, the mixing and stratification at the 60km river mouth area is highly complicated by partial and stratified mixing. Therefore, freshwater will appear 30km from the river mouth during the dry season to serve agricultural and domestic demand. Simultaneously, the study identifies the salt wedge location to support aquaculture cultivation.