Seasonal and Tidal Influence on Surface Water Quality – A Case Study in the Hau River Segment, Vietnamese Mekong Delta Province

The study aimed to evaluate the influence of seasons and tides on surface water quality of Hau River in Hau Giang province, Vietnam. The water quality data were collected at six locations at low tide and high tide. The monitoring parameters included pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), ammonium (NH4+-N), nitrate (NO3--N), orthophosphate (PO43--P), total phosphorus (TP), total nitrogen (TN), iron (Fe) and Coliform. One-way analysis of variance (One-way ANOVA), cluster analysis (CA) and discriminant analysis (DA) were applied to determine the influence of tides and seasons on water quality. The surface water quality was compared with the national technical regulation on surface water quality in column A1 (QCVN 08-MT:2015/BTNMT). The results showed that surface water in the study area had organic pollution and high eutrophication potential. The BOD, COD, TN, TP, Fe and coliform parameters in low tide tended to be higher than those in high tide. Five parameters, including TSS, TP, TN, PO43--P and coliform had a significant difference between the wet season and the dry season by DA analysis. Cluster analysis classified the water quality into three clusters, mainly by the BOD, COD, TSS, PO43--P and Fe parameters. The study provides important information on the water quality of the Hau River in the Hau Giang province for water uses and monitoring.