Hydro-Climatic Modelling of an Ungauged Basin in Kumasi, Ghana

Abstract. The 13 km² Owabi catchment provides about 20 % of water needs of the Kumasi metropolis has in recent times been prone to high anthropogenic activities, a source of worry to water resource management. A complementary hydro-climatic study of Owabi watershed has been carried out using Soil-Water-Assessment-Tool (SWAT) with the aim of simulating the stream-flow and water balance of the watershed and to predict its future state. The QGIS interface was used to launch SWAT for QSWAT. Stream-flow output from the model was calibrated against an empirically derived stream-flow dataset for Owabi and the efficacy of the technique tested. The SUFI-2 algorithm was used for calibration and validation on both daily and monthly temporal resolutions. Water loss from the catchment was due to evapotranspiration process followed by surface runoff. The model showed better prediction and low uncertainty for both calibration and validation at the monthly than daily timescale. From 2020 to 2050 under Representative Concentration Pathway 8.5 (RCP8.5), catchment water loss is expected to shift from the dominant evapotranspiraton to surface runoff. This would lead to increases in water yield and stream-flow amount. In general, the use of the SWAT model for hydrological assessment of the Owabi catchment has been successful and further studies on the assessment of water quality and pollution is currently being undertaken to provide a holistic view of water resource management at the catchment. This would aid effective decision making by water resource managers and boost water production for the Kumasi metropolis in the long-term.