A year-long simulation of the Mekong river plume is conducted. The purpose is to identify the main processes impacting the fate of tropical freshwater runoff onto the shelf for later inclusion into a global ocean circulation model. Factors influencing the river plume in a general case are listed and are included in a coastal ocean configuration of the Princeton Ocean Model. This is achieved either explicitly, as for wind forcing, or using parametrizations corresponding to the length and timescales of river plumes physics, as for tides or estuaries. Results exhibit a strong seasonal variability related to the monsoon wind and river flow regimes of the region. A comparison with in situ measurements made during a campaign carried out in 1997 shows a good agreement. Vertical salinity profiles extracted from the model configuration correspond to conductivity-temperature-depth salinity profiles behavior established during the campaign. This model configuration also provides a good estimate of sea surface salinity in the vicinity of the coast of the Mekong Delta.