The water quality and tidal nature of Woji River have been experimentally studied. Experimental data monitored within the hours of 07:00 h and 19:00 h in the course of the study include tidal current river depth and width, suspended solids (SS), dissolved oxygen (DO), biochemical oxygen demand (BOD), and ammonia-nitrogen. The water quality of Woji River was evaluated using the River Pollution Index (RPI). Results indicate that tide peaks within the hours 11:00 h to 13:00 h and recede within the hours of 17:00. Maximum tide level was 1.80 m and the minimum value was 0.77 m. At the high tide, measured width varied between 110-121.8 m and at lower ebb, width of the river varied between 47.2 m and 51.2 m. At peak tide water flows at an average speed of 1.36 m/s in the South West direction and at ebb tide River flows in the reverse direction at a constant speed of 0.12 m/s. Physico-chemical characteristics showed DO values ranged between 2.00 and 3.55 with a mean of 2.75 mg/L. Suspended solids (SS) values ranged between 4,100-8,150 mg/L with a mean value of 6713.08 mg/L. Observed BOD levels at sampling point ranged between 9.50-17.60 mg/L with a mean of 13.33 mg/L. Ammonia-nitrogen levels at sampling point ranged between 1.90-5.60 mg/L with a mean value of 3.38 mg/L. River Pollution Index (RPI) of above 6.0 was obtained and hence water quality is classified as severely polluted. The water quality is severely polluted and unacceptable for drinking and domestic purposes and will require best management practice to improve the water quality.

Keywords: River Pollution Index; Tidal Stream; Water Quality; Woji River;