Water samples of the Tien river - one of the important rivers at lower part of Mekongriver, flowing through the southern provinces of Vietnam - were collected in twosessions (1 - 7 June 2015 in the late dry season and 20 - 26 July 2015 in the earlyrainy season) at five selected sampling sites (from Hong Ngu district, Dong Thapprovince to Tien river estuary, Tien Giang province with the length of 230 km) formeasurement of water quality parameters such as temperature, pH, DO, TDS, TSS,COD, BOD5, ammonium, NO3-, PO43-, Fe, Mn and toxic metals (Hg, Cd, As, Pb, Ni,Cr, Cu, Zn). The obtained results shown that: due to saline intrusion from the sea,TDS rather high (3150 - 3267 ppm) at Tien river estuary area in the dry season; thecontents of TSS, COD and BOD5 were in the range of 9 - 475 ppm, 2 - 13 ppm and 2 -16 ppm, respectively; the contents of N-NH4 and P-PO4 were high in the range of0.02 - 0.60 ppm and 0.06 - 0.47 ppm, respectively; dissolved iron (Fe) andmanganese (Mn) concentrations were rather high with 1,600 - 31,000 ppb and 50 -1,000 ppb. Those parameters tends to increase in the river downstream and to behigher in the dry season. The dissolved toxic metal concentrations in the river waterwere low and met to class A of national technical regulation on surface water qualityQCVN 08:2008/BTNMT. There was the linear regressions between the contents ofTDS, TSS and the concentrations of Fe, Mn, toxic metals with correlation coefficient(R) 0,66 (p < 0,05) and R > 0,77 (p < 0,01). The linear correlation between thetoxic metal concentrations was also found with R 0,79 (p < 0,01).
