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Water quality index was estimated using the modified Brown et al.,(1972) equation for the Isiodu freshwater habitat during dredging processes. Ten parameters were analysed using recommended standard methods and the water quality index was calculated for each. These parameters include fecal coliform count, biochemical oxygen demand (BOD5), dissolved oxygen (DO), hydrogen ion concentration (pH), temperature, total dissolved solids (TDS), phosphate, Turbidity, Nitrate and ammonia. The estimated water quality index for the studied parameters during the dry seasons of November and December are given respectively as, fecal coliform count (4.68, 7.47), BOD5 (1.21, 1.29mg/L), DO (5.34, 5.37mg/L), pH (6.25, 623), temperature (5.81, 6.29oC), TDS (104.36, 104.21mg/L), PO4 (3.76, 3.78mg/L) Turbidity (132, 1.32 NTU), Nitrate (0.0023, 0.0024mg/L) and ammonia (1.23, 1.29mg/L). Similarly during the wet season of June and July, the water quality index are fecal coliform count (6.96, 7.57mg/L), BOD5 (3.21, 3.17mg/L) DO (5.47, 5.36mg/L), pH (6.87, 6.86), temperature (13.20, 8.93oC), TDS (71.02, 101.98mg/L), phosphate (3.37, 3.39mg/L), turbidity (1.57, 1.68 NTU), Nitrate (0.002, 0.002mg/L) and ammonia (0.83, 0.85mg/L) respectively. Most of the parameters were within recommended limits but care must be taken to avoid further accumulation leading to lethal effects on the plankton community.
KEYWORDS: Water quality Index, Isiodu River, freshwater, dredging, pollutants.