This study was conducted to assess the surface water quality of the Mekong River in the basins affected by urban areas (5 sampling points) and industrial parks/clusters (2 sampling points) in An Giang province by sampling surface water in June, 2021 (dry season), analyzing the parameters of temperature, pH, DO, TSS, COD, BOD₅, NO₃^-, NH₄⁺, PO₄^3-, Coliform, As, Pb, Hg, Benzene hexachloride, Dieldrin. The analytical results of water samples were compared with the National Technical Regulation on surface water quality of Vietnam. The water quality index was calculated according to the technical guidelines for calculation and publication of the water quality index of the Vietnam Environment Administration (VN_WQI). The results show that domestic and industrial wastewater have polluted the surface water of the Tien river and the Hau river - two important rivers of the downstream Mekong river - flowing through An Giang province. The pollution shows in parameters of TSS, DO, BOD₅, COD, NH₄⁺, Coliform that exceeds allowable limits. Other parameters such as temperature, pH, NO₃^-, PO₄^3- are mostly at the acceptable range and within allowable limits. The water quality is lowest in Cai Dau urban area - Chau Phu district (on the Hau river). Based on the WQI, most of the water quality at the sampling points is poor – it is usable for water transport and similar purposes, requiring appropriate treatment before use for living purposes and need to have appropriate water quality management measures.

Keywords: water quality, Mekong surface water, domestic wastewater, industrial wastewater