Estimation of stream discharge of ungauged basins using NRCS-CN and remote sensing methods: A case study of Okhuwan and Okhaihe catchments, Benin City, Edo State, Nigeria

The study aims to utilize the NRCS-CN and remote sensing methods in estimating streamflow of Okhuwan and Okhaihe catchments. Remote sensing data, coupled with GIS techniques were used to estimate seasonal rainfall and streamflow. Measured rainfall data was collected from the Nigerian Meteorological Service, while field measurement of streamflow was carried to generate baseline data. Measured rainfall and streamflow were correlated with estimated rainfall and streamflows as indicators of our model effectiveness. The coefficients of determination between estimated rainfall and measure rainfall ranged from 0.67 to 0.77 in Okhuwan basin and from 0.71 to 0.75 in Okhaihe basin, suggesting good correlation in both data as well as suitability of use for streamflow estimation. Stream flow rises sharply with the onset of the rainy season in April and persists till July and August with streamflow, reaching a maximum of 174.0 and 237.3 m3/s in Okhuwan and Okhaihe, respectively. Regression residuals were within small range, an indication that measured and estimated data exhibit some closeness particularly in low discharge values. Very strong positive relationship was observed between measured and estimated streamflow. Overall findings showed that in the absence of hydrological information, regional models can serve for data generation. Key words: Streamflow estimation, River Basin, hydrological data, NRCS-CN, river flooding.