Abstract
This study investigated the physicochemical limnology and seasonal water quality dynamics of Igbidin Stream in Edo State, Nigeria. Monthly water samples were collected from three stations between January and June 2018, spanning both dry and wet seasons. Parameters analyzed included temperature, pH, turbidity, color, total dissolved solids (TDS), conductivity, alkalinity, total hardness, calcium, magnesium, nitrate, and phosphate. The results revealed marked seasonal variations, with elevated turbidity (up to 21 NTU), conductivity (up to 207.5 µS/cm), and TDS (up to 125 mg/L) during the dry season. Colour values peaked at 99 PtCoU in February, far exceeding WHO limits. Nitrate and phosphate concentrations remained generally low, with nitrate ranging from 0.005 to 0.053 mg/L and phosphate from 0.19 to 0.46 mg/L, although phosphate occasionally surpassed ecological thresholds. The pH showed significant seasonal fluctuation, peaking at 10.7 in April. The physical pollution index (PPI) remained above 1 throughout the study, indicating consistent pollution, particularly in the dry season. Water Quality Index (WQI) values showed significant spatial and temporal variation, with April exhibiting the poorest quality (mean WQI: 116.8), classifying the water as unsuitable for drinking. In contrast, June showed the best quality (mean WQI: 16.28), rated as excellent. Stations 1 and 2 were more affected by pollution, likely due to nearby anthropogenic activities such as farming, while Station 3 exhibited relatively stable and better water quality. The findings underscore the need for seasonal monitoring, targeted pollution mitigation, and provision of water treatment interventions, especially during high-risk months.