Fitting Rating Curves to Selected Streams in Southeast Nigeria

Abstract

Lack of funds and political will has made continuous gauging of rivers in Nigeria impossible, thus stalling the development of surface water resources. In order to address this anomaly; this study is focused on developing discharge rating curve, for selected streams in Imo-Anambra river basin of southeast Nigeria, which is capable of predicting discharge from stage. Ten years monthly stage and discharge records, measured with stream gauges, for Rivers Adada in Enugu state, Ajali in Anambra state, Ivo in Ebonyi State, Otamiri in Imo state,  and Imo (Umuopara) in Abia state, were used in estimating the rating curve models using simple linear regression as: ,  and . All the rating curve equations were validated using coefficient of determination which yielded values of 98.54%, 97.38%, 17.31%, 89.98% and 99.43%, but the empirical discharge-stage model of River Ivo was discarded as the model produced poor performance and lacked the features of a rating curve. The rating curve of Imo River predicted the highest discharge for equivalent input values of stage because of its large cross-section at the gauging station. The developed rating curve models are therefore recommended for discharge prediction in these catchment areas with limited streamflow records. Keywords — fitting, rating curve, southeast Nigeria, stream discharge