Impact of Rainfall on Physio-Chemical Parameters of Erinle Dam Water

This study investigated the impact of rainfall on the physicochemical characteristics of Erinle Dam, with emphasis on seasonal and spatial variations in water quality. Water samples were collected from three sampling locations representing the inlet, middle and outlet of the dam during three hydrological periods: peak dry season (PDS), beginning of rainy season (BRS) and peak rainy season (PRS). The samples were analysed for selected physicochemical parameters, including temperature, turbidity, colour, total dissolved solids (TDS), total suspended solids (TSS), pH, dissolved oxygen (DO) and biochemical oxygen demand (BOD). The results demonstrated noticeable variations in several physicochemical parameters across seasons and sampling locations, indicating that rainfall and associated runoff influenced the water quality of Erinle Dam. Parameters such as turbidity, colour, TSS and other runoff-sensitive variables generally showed greater variation during the rainy periods, which can be attributed to the introduction of soil particles, organic matter and dissolved substances into the reservoir through surface runoff. Variations in pH, dissolved oxygen and other chemical parameters also reflected changes in dilution, organic loading, aeration and biological activity associated with changing hydrological conditions. The findings indicate that rainfall is an important factor influencing the physicochemical condition of Erinle Dam and that both season and sampling location should be considered in water-quality management. Continuous monitoring of the reservoir is therefore necessary to detect seasonal deterioration and maintain its suitability for domestic, agricultural and ecological uses.