Characterization of the impacts of climate change on meteorological and hydrological drought in the koliba-corubal watershed of Guinea and Guinea-Bissau region

Conceptual overview of the study framework showing climate projections, hydrological modeling, drought index calculations, and projected impacts of climate change on meteorological and hydrological droughts in the Koliba-Corubal Basin. Results indicate increasing drought frequency, duration, and severity under future climate scenarios. Climate change poses a major threat to water resources in West Africa. This study analyzes the impacts of climate change on meteorological and hydrological droughts in the Koliba-Corubal transboundary basin by 2100. Based on CMIP6 projections under the SSP1-2.6 and SSP5-8.5 scenarios, four climate models were used to estimate changes in rainfall and temperature. Future streamflows were simulated using the GR4J hydrological model. The standardized indices SPI, SPEI, and SSI were calculated at 3, 6, 12, and 24-month timescales to characterize droughts. The results reveal a trend toward worsening droughts, particularly pronounced under the SSP5-8.5 scenario. The frequency of extreme drought increases significantly, with the proportion of dry years reaching 93.1% for the SSI24 hydrological index by the end of the century. The duration and severity of drought episodes are lengthening, while correlation analysis shows a strengthening of the links between meteorological and hydrological droughts (R2 up to 0.93). These results call for the development of integrated adaptation strategies to preserve the water resources of this vital basin.