Assessment of morphological and hydrological parameters of Oyun River Basin, Nigeria

Abstract

The study involves evaluation of basin area, slopes, shape of the basin as morphological parameters and analysis of flow frequencies for flood and low flows, developing unit hydrograph and analysis of rainfall intensity distribution in the study area as hydrological parameters. The morphological analysis of the basin yielded basin area, slope, elongation and circulatory ratio of 830km², 0.57%, 0.46 and 0.35 respectively. For hydrological analysis, flow frequency, unit hydrograph and rainfall analysis were evaluated. The flood (peak) and low flows were fitted with Gumbel Extreme Value Type I & III model, and the recurrence intervals for low and peak flows of 0.0004m³/s and 3.5772m³/s were obtained as 4 and 44 years respectively. The mean annual maximum flow and mean annual runoff depth were estimated to be 7.97m³/s and 6.5mm respectively. This showed that the intensity of rainfall contributing to the volume of river discharge was 6.5mm/day. Unit hydrograph was developed for the river basin using SCS approach. More so, rainfall analysis was carried out to determine the flood and drought periods. The results indicated that Oyun river basin is relatively small watershed with elongated narrow shape and non-steep slope which contributed to relatively slower draining of water into the river. From the analysis, flooding is expected in the month of September while drought may be expected in the months of December to February. The results of this study will be useful to river basin managers in managing and planning of water resources and facilities development.

Keywords: Hydrological, Morphological, River basin, SCS, Flood, Low flow