Abstract:
This research assessed the water resources potential of Osun River Basin for data
generation in river projects planning and design. The river takes its source from
Igede-Ekiti in Southwestern Nigeria and discharges into Lagos lagoon in Gulf of
Guinea. Direct measurement of the discharge at some points along a river has a
reasonable cost implication and it is time consuming. This can similarly be achieved by
using stage- discharge relationship (Rating Curve). The retaining capacity of the Osun
River could be estimated using mass curve diagram developed in the study.
Hydrological study of Osun river basin was done from the available rainfall and stream
flow records of years 1982 -2013. The data was taken from the Hydrometric
Department of the Ogun-Osun River Basin Development Authority (OORBDA). The
Rainfall analysis indicated no apparent trend. The flood frequency analysis of Osun
River was carried out using Gumbel’s distribution and Powell’s distribution. Maximum
flood discharges were estimated for different recurrence intervals of 2, 5, 10, 25, 50,
100, 200 and 400 years. Powell distribution forecast higher flood for the different
return periods which makes the method more acceptable in designing an erosion
mitigating structures. The study would contribute to the knowledge of hydrology of
Osun River. The data obtained in this study would be useful information for future
studies of the basin. The study would further contribute to the improvement of future
water resources development plans in the region.
