In recent years, saltwater intrusion in river estuaries has become more severe and frequent worldwide. The common reasons lie in increasing freshwater withdrawal, river flow regulation and sea level rise due to global warming. In particular, the Red River Delta in northern Vietnam is facing a strong population growth worsening the pressure on freshwater resources for drinking water and irrigation needs. During the dry season, increasing conflicts and constraints in freshwater availability have already been experienced. Adverse combinations of river flow regulations and high sea levels lead to severe upstream propagations of salinity. This study takes advantage of a statistical characterization of discharges released from Hoa Binh reservoir and observed at Son Tay station, the main river flow control upstream of the river delta, along with downscaled and updated sea level rise scenarios to estimate the future extents of saltwater intrusion under different options of water release from reservoirs in the dry season. To do so, a 1D hydraulic model of the river delta network was implemented using MIKE11 software. The hydraulic and the quality modules were calibrated and validated with respect to the present scenario by using water stages and salinity concentrations observed in estuary branches. Sea level rise projections for 2050 and 2100 referred to RCP4.5 and RCP8.5 AR5 emission scenarios were then considered. Results show that river flow regulation can provide an effective mitigation measure. A 20–30% increase in the discharge released from the Son Tay station would be beneficial to push downstream the saltwater intrusion in the main Red River branch during the dry season. For instance, in 2050 the 1‰ salt concentration front is expected to be pushed back at least 6 km when the exceeding probability of the discharge released by Son Tay station decreases from 95% to 25%.

近年来，世界范围内河口海水入侵变得更加严重和频繁。常见的原因是全球变暖导致淡水抽取量增加、河流流量调节和海平面上升。特别是，越南北部的红河三角洲正面临着人口的强劲增长，加剧了饮用水和灌溉需求淡水资源的压力。在旱季，淡水供应方面的冲突和限制已经日益增加。河流流量调节和高海平面的不利组合导致盐度严重向上游传播。这项研究利用了和平水库排放的统计特征以及在山西站（三角洲上游的主要河流流量控制）观测到的流量的统计特征，以及缩小和更新的海平面上升情景来估计未来咸水入侵的程度旱季水库放水的不同选择。为此，使用 MIKE11 软件构建了三角洲网络的一维水力模型。通过使用在河口支流中观察到的水位和盐度浓度，根据当前情况对水力和质量模块进行了校准和验证。然后考虑了参考 RCP4.5 和 RCP8.5 AR5 排放情景的 2050 年和 2100 年海平面上升预测。结果表明，河流流量调节可以提供有效的缓解措施。山西水站排放量增加 20-30% 将有利于在旱季将红河主干的咸水入侵推向下游。例如，到2050年，当山西站排放超标概率从95%下降到25%时，预计1‰盐浓度前沿将向后推后至少6公里。