The East Sea tide in Soai Rap estuary has amplitude of high from 3,5 to 3,9 m. The process of intruding salt water is deeper and longer into the inland. The reason is the strong operation of tide, northeast wind, less water from upstream and especially many exploitations of surface water in dry season. In the past, Vam Co Tay river had been intruded by salt water in Tuyen Nhon of about 5 km, since 1993, it has reached to Vinh Hung. The salinization has started from January to June with 2 - 4 gam/liters. The salinity of Vam Co Dong river has gradually reduced by the influence of Dau Tieng lake.

Besides, the earth tends to be hotter, facilitating sea level raising, developing the salinization deeply to inland.

The salinization has changed the ecological system of region which has been stable for many years, resulting in the influence to production and daily life of people. To reduce this process, should not exploit too much in dry season and the investment in irrigation systems should consider the impact of salt water intrusion on the general ecological system.