Assessment of water quality in coastal estuaries under the impact of an industrial zone in Hai Phong, Vietnam

The purpose of this study was to apply numerical modeling to assess the water quality in Nam Trieu and Lach Tray coastal estuaries. The wind reanalysis data from the Weather Research and Forecasting (WRF) Model were used to simulate waves and hydrodynamic regimes with a definition of 14 km within the longitude range from 105oE to 120oE and latitude range from 5° to 22° in the study area. The calibration and validation results for the wind–wave, hydrodynamic regimes showed that the performance of the 2D hydrodynamic model is extremely good, with a Nash coefficient ranging from 0.89 to 0.92, a root–mean–square error (RMSE) observation standard deviation ratio (RSR) varying from 0.25 to 3.6, and a percent bias (PBIAS) from −4.2% to 0.2%. The calibrated 2D hydrodynamic model was combined with the Ecolab model to evaluate and simulate the spreading of water quality parameters (biochemical oxygen demand (BOD), NH4+-N, and total suspended solids (TSS)). The water quality parameters BOD (16.5–22.5 mg/l), NH4+-N (0.003–0.009 mg/l), and TSS (29.63–40.8 mg/l) were smaller than the parameters of the national technical regulation on coastal water quality and surface water quality in March and August. The assessment results of water quality an industrial zone can help in management, planning, and decision–making to reduce wastewater discharge.