The study was carried out to investigate the seasonal variations in physico-chemical and biological parameters of Awon Reservoir for a period of twelve months January 2009 to December 2009. Water samples were collected on monthly basis and were analyzed for water temperature, pH, phosphate phosphorus and Nitrate Nitrogen. The results revealed four divisions of Phytoplankton namely Bacillariophyta, Chlorophyta, Cyanophyta and Euglenophyta. The highest number of cells, was recorded during the dry months when nitrate and phosphate values were high. The parameters were analyzed to investigate probable pollution and suggest ways to conserve phytoplanktonic life in Awon reservoir. The different parameters used in the study showed that quality of water is within save limits and good to support the phytoplankton and other biota in Awon reservoir.
