A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 2005

The Red River Delta is one of the two biggest rice fields and the largest salt-culture field in Vietnam. In dry season, for the lack of fresh water from upstream, salinity intrusion problem causes a lot of difficulties for irrigation and aquaculture. The knowledge of the characteristics of flow and salinity intrusion therefore is very important for utilization of the river estuaries. Characteristics of flow and salinity intrusion in the river delta are investigated based on many year recorded data of salinity and hydraulic characteristics at stations along Red River and its branched. MIKE11 Model is employed to simulate the hydraulics characteristics and salinity intrusion for all cases as well as scenarios in the Red River Delta. The effect of Hoabinh and Sonla Hydropower Plant in salinity intrusion in Red and Thaibinh River has been investigated. The computed results present that salinity concentration at the same location before Hoabinh Hydropower Plant has been constructed is over twine the value at the present. On the other hand, the changing of salinity concentration as well as the length of intruded salt after Sonla Hydropower Plant is going to completely construct is negligible. Therefore, it could be confirmed that the inflow from Hoabinh Hydropower Plant plays important role in pushing of salinity in Red River Delta while the effect Sonla Hydropower Plant to salinity intrusion is not intensive. The effect of sea level rise on flow characteristics of the Red River Delta has been detected under various magnitude orders of rising sea level and flow enter into the Red River Delta with nine scenarios due to the Greenhouse Effect during the dry season by the years 2010, 2050, 2100. These information are useful picture knew as a forecasting the variation of the water level, fresh water discharge distribution and salinity intrusion in the Red River Delta. The range of increase of salinity at every distance in nine scenarios varied within value of 0.5-1psu. These results have confirmed that with climate change, the variation of salinity intrusion into Red River Delta is not much.