| Salinity intrusion in the Hau and Tien Rivers, which split into four main estuaries of the Mekong River (MR), is controlled by the river discharge, tides, waves, currents, winds, topography, and bathmetry. Salinity instrusion in these estuaries is substantially increasing in recent years. For instance, the most severe salinity intrusion appeared in 2016 over the past 90 years, and salinity concentration was abnormally high in the beginning of the dry season 2020. Such recently increased salinity intrusion is caused by significant changes of the upstream flow regimes and the increased tidal amplitude of 2.61mm/year . This study investigates recent dynamic characteristics of salinity intrusion in the Hau and Tien Rivers under the impact of the tide and river discharge on maximum salinity concentration and intrusion length by employing MIKE 1D numerical models.<br>
The results show that upstream river discharge can dilute saltwater along the MR while tides increased salinity concentration. Maximum salinity concentrations appeared 3-5 days before the Spring tide. Additinally, during one tidal cycle, the maximum salinity concentration lagged 1-2 hours after the maximum water level. Moreover, at the esturaries, hourly maximum intrusion length usually appeared after the tidal peak by about 3-4 hours. Finally, regression models were developed to correlate the river discharge and the tide to the intrusion length.<br>
The results are supportive for the operation of sluice gates and pumping stations to intake and store fresh water. Futhermore, the devepled regression functions can predict salinity concentrations when the upstream discharges are known, whichcan provide some guidances for the operation the upstream dams to control salinity intrusion. |
