Seasonal variation in the physicochemistry of a small tropical reservoir (Aiba Reservoir, Iwo, Osun, Nigeria)

Aiba Reservoir was sampled between March, 2004 and February, 2005 for physico-chemical studies. Air temperatures ranged from 20.00 – 30.50oC (mean ± s.e: 26.33 ± 0.26oC), water temperature ranged from 25.00 – 35.00oC (mean ± s.e: 29.26 ± 0.19oC), pH ranged from 5.53 - 9.48 (mean ± s.e: 7.98 ± 0.11), dissolved oxygen ranged from 1.75 – 11.20 mgO2/l (mean ± s.e: 7.23 ± 0.20 mgO2/l), alkalinity ranged from 42.50 – 85.00 mg/l (mean ± s.e: 65.20 ± 0.85 mg/l), total hardness ranged from 12.00–59.00 mg/lCaCO3 (mean ± s.e: 45.13 ± 0.90 mg/lCaCO3), conductivity ranged from 6.80 – 126.40 mV (mean ± s.e: 67.03 ± 4.04 mV), and turbidity ranged from 12.50 – 143.75 FTU (mean ± s.e: 40.74 ± 3.60 FTU). The physico-chemistry of Aiba Reservoir exhibited spatio-temporal variation. Two-way analysis of variance of physico-chemical parameters showed obvious seasonality for pH, conductivity and turbidity, suggesting that these parameters play major roles in the limnology of the reservoir. Factor analysis shows pH, conductivity, temperature and dissolved oxygen as important parameters contributing to the annual variability. Dissolved oxygen is a more important parameter during the wet season, while alkalinity is more important during the dry season for the reservoir. Hardness and alkalinity values suggest that the reservoir water is good for aquaculture.