Application of Geospatial Technology in Watershed Delineation and Extraction of Hydrologic Characteristics in Opa Catchment, Southwestern Nigeria

This study explored the opportunity offered by geospatial technology to delineate the watershed draining surface water into Opa River, Southwest Nigeria and its tributaries using a selected outlet downstream of Opa reservoir and then carried out extraction of hydrologic characteristics of the watershed. The automated delineation procedure of ArcHydro extension of ArcGIS software was used. The watershed delineated has coverage of 197.21 km2 and 17 sub-watersheds. Hydrologic Engineering Centre-Geospatial Hydrologic Modelling Extension (HEC-GeoHMS) was used to extract the hydrologic characteristic of the sub-watershed such as area, basin slope, river slope, centroid elevation and longest flow length. The division of the catchment into sub-watersheds enables matching the characteristics of each unit with soil and and land use characteristics thereby making watershed management at micro scale easier.