Climate change impact on streamflow in a tropical basin of Ghana, West Africa

Abstract

Study region: Pra River Basin, Ghana, West Africa. Study focus: In this study, variations of the future streamflow in the Pra River Basin (PRB), are projected using the Soil and Water Analysis Tool (SWAT) model with bias-corrected climate data from regional climate models (RCMs) for the near 21 st century (2010–2039), the mid 21 st century (2040–2069), and the end of the 21 st century (2070–2099), under two Representative Concentration Pathways (RCP4.5 and RCP8.5). Weighting, scaling and ranking techniques were applied to the data from each of the seventeen climate stations to select the climate models that best reproduced the observation dataset. New hydrological insights for the region: The results from the calibration and validation (R2 and NSE > 0.75, and PBIAS within ±10 %), revealed good simulation of the PRB hydrology from the SWAT model. Annually, streamflow in the near and the mid-21st century is projected to increase within 4 % and 12 % while a reduction was projected at the end of the 21 st century with the RCP4.5 emission scenario. The simulation results from the RCP8.5 scenario showed increase streamflow throughout the 21 st century applying the best performing models. Monthly streamflow variations varied between -15 % and 23 % for RCP4.5, and -24 % to 24 % for RCP8.5. Generally, increasing streamflow was highest in the RCP4.5 emission scenario. In view of the model outcomes, the PRB is expected to experience upsurge in streamflow by the near and the mid of the 21 st century. This would require proper planning by applying cost-effective adaptative water management strategies to provide for the probable influence of climate change on the future water resources of the basin.

Keywords

• Weighting, scaling and ranking techniques
• Climate impact
• Hydrological model
• Streamflow
• Pra River Basin