Evaluating Climate Change Scenarios in the White Volta Basin: A Statistical Bias-Correction Approach

Abstract

This study provides a critical assessment of future climate scenarios in the White Volta Basin (WVB), an area heavily reliant on groundwater resources. Seven Regional Climate Models were employed from the Coupled Model Intercomparison Project Phase 6 (CMIP6) under Shared Socioeconomic Pathway Scenarios (SSPs) SSP2-4.5 and SSP5-8.5. The Climate Change for Watershed Modeling (CMhyd) software was used for bias correction of these models, with observational data sourced from the National Centers for Environmental Prediction's Climate Forecast System Reanalysis (NCEP CFSR) and 12 gridded climate stations. The bias-corrected models validated using R2, NSE, RMSE, PBIAS, and additional metrics, demonstrated good calibration compared to observed data. Precipitation ensembles showed 97-99% R2, 94-99% NSE, 70-485mm RMSE, and -9-5% PBIAS. Tmax and Tmin bias correction performances varied with the respective metric values fell within acceptable ranges. Overall, precipitation levels are expected to decline for SSP2-4.5, while SSP5-8.5 are expected to increase until 2075 across all scenarios in comparison to the baseline period. Tmax will be considerably high under SSP5-8.5, with an estimated increase of around 43 0C/year in comparison to the reference period. The monthly average variation in the maximum temperature ranges from 0.62 to 2.43 0C. With the SSP5-8.5 scenario. These findings reveal the potential impacts of climate change on agricultural productivity and groundwater recharge, crucial information for the development of Ghana's National Determined Contributions (NDCs) and National Adaptation Plans (NAPs). Thus, emphasizing the need for comprehensive adaptation strategies to mitigate the climate change impact on water resources and ecosystem services.

Keywords: White Volta Basin, CMIP6, Bias correction, Climate Change, Socioeconomic Scenarios, Hydrology