This study was conducted to evaluate surface water quality in rivers and canals in the Plain of Reeds, Dong Thap province for the year 2020 using national technical regulation on surface water quality (QCVN 08-MT: 2015/BTNMT) and water quality index (WQI). Surface water quality parameters of turbidity, pH, temperature, dissolved oxygen (DO), suspended solids (TSS), biological oxygen demand (BOD), chemical oxygen demand (COD), nitrite (N-NO₂^-), nitrate (N-NO₃^-), ammonium (N-NH₄⁺), orthophosphate (P-PO₄^3-), coliform, and E.coli. The results showed that BOD, COD, coliform and E.coli at most of the monitoring locations exceeded QCVN 08-MT: 2015/BTNMT, column A2 pointing out that surface water quality was being seriously impaired. Temperature, pH, DO, and E. coli were not significantly different between the seasons. TSS, BOD, COD, N-NH₄⁺, N-NO₃^-, P-PO₄^3-, and coliform were high in the rainy season while N-NO₂^- was high in the dry season. WQI values ranging from 24 to 64 indicated the poor water quality in densely populated, industrial areas along Tien and Hau rivers. Further studies should focus on specific water polluting sources for sustainable surface water quality management.

Keywords: surface water quality, organic pollution, suspended solids, coliforms, Vietnamese standards, Plain of Reeds