Development of rating equation for lower river Ogun, South-Western, Nigeria

River discharge is a variable which is separated from other component of the system, it is directly influenced by surface and subsurface runoff but influences fresh water influxes into the ocean. The rating equation is widely adopted where the measurement of discharge is difficult most especially in developing countries. Most Rivers in Nigeria has frequent occurrence of flooding. This study developed a stage and discharge relationship for Lower River Ogun in Nigeria. The stage and discharge relationship was established using measured and collected data. The velocity of water flow was measured using flow meter and gauge were measured with automated stage level. The generated rating equation: Q = 169.1(G-a)0.099 m/s3 with coefficient regression 79%. The generated equation was calibrated and validated with discharge data collected from 2005 to 2018. The rating equation curve performed better at depth 3.63m with percentage variation between measured and simulated discharge of 5.43%. The rating equation can be adapted to other rivers with similar catchment and geological characteristics. The Lower River Ogun serve as the permanent control and the rating equation is reliable.