Comparability Studies of High and Low Resolution Digital Elevation Models for Watershed Delineation in the Tropics: Case of Densu River Basin of Ghana

Abstract

The Densu River Basin is one of the most important basins in Ghana acting as a source of potable water and habitat for vital aquatic species. In order to understand the basin’s characteristics and eventually plan and monitor water resources, reliable watershed’s properties are important. GIS methods have proven to provide more reliable methods for watershed delineation compared to traditional techniques.  In answer to this, this study employed the use of both high and low resolution Digital Elevation Models (DEMs) from ASTER and Shuttle Radar Topography Mission (SRTM) respectively to delineate the watershed of the Densu River Basin. This is because Advanced Spaceborne Thermal Emission and Reflection (ASTER) 30m DEM and SRTM 90m DEM are freely available globally. The results indicated that both DEMs have a good representation of the watershed of the Densu River Basin. The coarser resolution, SRTM, produce a better closeness in terms of watershed area and representation compared to the ASTER. For sensitivity modelling such as flood forecasting, on the contrary, ASTER is apparently better as a result of high accuracy in the estimation of the longest flow length of the river. This study hopes to contribute towards the application of the methods used in this research for other basins in Ghana and other parts in the West Africa sub-region which do not have accurate watersheds for water resources planning and management.