Following the concrete structure erected in Ogbei Stream, Nkpologwu Anambra State, Nigeria in 2005, changes in physical and chemical characteristics were monitored for twelve months (May 2008 – April 2009). Six sampling stations were selected for study. The water samples for physical and chemical characteristics of the stream was collected and analysed. Result of physical and chemical characteristics revealed that water temperature consistently followed the ambient temperature. The high mean water temperature in station 1 (29.07±0.11 C) was significantly difference (p<0.05) from the values recorded for all other stations. The concrete structure erected in this station 1 was responsible for the high temperature observed in the station. The maximum mean water velocity and the lowest mean depth in station may be attributed to concrete structure erected in this station as well as evaporation caused by deforestation and logging. The highest mean nitrate-nitrogen (0.04±0.07 mg/l) in station 1 which was not significantly different (p>0.05) from the values of all other stations was due to fertilizer applied to farms along the stream bank in addition to increase in organic matter due to deforestation.

Keywords : Impact, Concrete Structure, Physical and Chemical Characteristics, Ogbei Stream