Impacts of Climate Variability and Change on Hydrological Dynamics in the Koliba-Corubal Basin (Guinea and Guinea-Bissau): Modelling Historical and Future Flows by GR4J under CMIP6 Climate Scenarios

ABSTRACT: The Koliba-Corubal basin, located between Guinea and Guinea-Bissau, is a key area for water resource management, but it is vulnerable to the effects of climate change. This article aims to analyze historical and future hydrological trends in this basin using the GR4J hydrological model in order to assess the impact of climate change on water availability. The study is based on past climate data (1981–1993) and future projections from CMIP6 climate models, applied to three climate change scenarios: SSP 126, SSP 370, and SSP 585. The results show a significant decrease in river flows in the basin, with reductions of up to 65.6% by the end of the century, especially under the SSP 370 and SSP 585 scenarios. Dry periods are especially affected, with a marked decline in monthly flows, seriously impacting water resource management for agriculture and drinking water supply. Using Mann-Kendall and Pettitt statistical tests, the study also identifies potential breaks in the time series of flows. The results of this analysis highlight the urgency of adopting climate change adaptation strategies and the need for sustainable water resource management in the Koliba-Corubal basin to meet the challenges posed by these changes.