SURFACE MAP OF STUDY AREA

ABSTRACT Erelu reservoir in Oyo town with default area of 161.07 hectares was constructed in 1961 on the Awon River, it was designed to supply potable water to the local community and adjacent areas. While the reservoir provides considerable benefits and has been the subject of various investigations, a significant gap exists in the comprehensive analysis of its physical characteristics. This oversight might pose possible potential environmental hazards if not indicated. This investigation addresses this deficiency by focusing on the characterization of the Erelu riverbed, an area identified as lacking in previous research. Supplementary interviews revealed the presence of potentially hazardous underwater features. To this end, a specialized survey boat equipped with a South SDE 28S+ Echosounder and a Starfish Side Scan Sonar, integrated with GPS receiver, was employed to assess and characterize the riverbed. These instruments facilitated detailed field operations, providing depth measurements and high-resolution imagery of the riverbed for hazard identification. Data processing and analysis were conducted utilizing Hypack 2018, ArcGIS 10.4, AutoCAD, SURFER 2020 and Starfish Scanline software. The bathymetric analysis revealed a depth range of 0.50m to 5.40m, with an average depth of 2.65m. Planimetric analysis indicated a surface area of 86.2 hectares, resulting in a calculated volume of 2,167,953.199646m3. The survey identified several submerged features, including rocks, a suspected submerged canoe, and other objects, all of which were precisely located. Based on these findings, it is recommended that warning signs be strategically placed at the identified locations to mitigate potential risks, and that dredging operations be considered to increase the reservoir's water volume.