Résumé
The Red River Delta (RRD) in northern Vietnam represents a complex hydrological ntework of tributaries and distributaries with a strong tidal influence due to the very flat relief. 20/100 of the total annual discharge of the Red River Basin flow through the Day-Nhue River system (DNR), which is one of the three main branches of the RRD. This sub-bassin, on the right bank where the city of Hanoi ils located, provides water supply to the main part of the totla population of the RRD. Very few studies have discussed the impact of the tidal movement in the river fluxes transported to the sea. The tidal influence on the river discharge has been investigated through several ADCP gauging measurements during repetitions of 24h-long surveys. Due to the tidal move, the instantaneous river discharge values describe a daily cycle with one daily maximum, one daily minimum and a short period of stream current at value zero. Our calculation recorded a daily range from + 150m3/s to -250m3/s. This inverse current implies a significant impact on the river fluxes transported to the estuarine zone. And the river discharge on the RRD cannot be calculated by a classical calibration equation linking water level and discharge, since there is no univocal relationship.