Studies on the effects of anthropogenic activities on the seasonal variation of Some Physico-Chemical Parameters in Ajiwa Reservoir, Katsina State, Nigeria was carried out from September, 2014 to August, 2015. Nineteen (19) physicochemical parameters were analysed at five different sampling locations in the reservoir. The physicochemical parameter was determined using standard methods, procedures, and instruments. Mean value of some of the physicochemical parameters in the reservoir that are beyond permissible limit include; Turbidity (98.0 ± 2.28 NTU), Total Hardness (87.16 ± 2.37 mg/l), Calcium (40.34 ± 1.35 mg/l), Nitrate-Nitrogen (1.07 ± 0.08 mg/l), Chloride (52.26 ± 1.65 mg/l), Magnesium (2.21 ± 0.14 mg/l) and Iron (0.50 ± 0.02 mg/l). The fluctuation of the physicochemical parameters of the reservoir could be attributed to farming activities, cattle rearing and bathing within the vicinity of the reservoir. Monitoring of human activities within the immediate catchment area of the reservoir and education on wise use of the water is recommended.
