The study was conducted to investigate the seasonal variation of water quality parameters of Tetulia River in Bhola, Bangladesh during the period from February 2019 to January 2020. The water samples were collected from five different sampling stations (ST-1: Bazar Khola, ST-2: Santirhat, ST-3: Bagmara, ST-4: Nayachar and ST-5: Kheyaghat) in pre-monsoon (Feb. to May), monsoon (Jun. to Sep.) and post-monsoon (Oct. to Jan.) season  to analyze the water temperature, pH, electrical conductivity (EC), dissolved oxygen (DO), biochemical oxygen demand (BOD) and total dissolve solid (TDS). Results showed that temperature, pH, EC, DO, BOD and TDS were ranged from 28.8 to 29.2, 27.4 to 28.5, and 24.2 to 26.8ºC; 6.3 to 6.76, 7.21 to 7.79, and 6.1 to 7.3; 162 to 174, 140 to 150, and 250 to 268µs/cm; 5.7 to 6.0, 7.1 to 7.6, and 6.0 to 6.8 mg/L; 2.5 to 2.8, 2.1 to 2.7, and 1.9 to 2.4 mg/L and 93 to 115, 71 to 80 and 130 to 140 mg/L; in the pre-monsoon, monsoon and post-monsoon season, respectively. The study also revealed that except BOD all explored parameters of coastal surface water were within the standard level and suitable for fisheries as well as aquatic species. However, according to the NSF method, the Tetulia River’s water quality was found to be in the medium cluster during the monsoon and post-monsoon seasons, whereas bad category was found during the pre-monsoon season for all of the investigated stations.

Key words: Seasonal change, water quality, water quality indices, Tetulia River