Projections of Hydrological Droughts under SSP5-8.5 Scenario in the Cautín River Basin, Chile, using hydrological models calibrated in the FUSE platform.

Over the past decades, extreme events like floods and droughts have become more frequent and intense, and future climate change scenarios may worsen this condition. Hence, we examine projected changes in drought characteristics under the SSP5-8.5 climate scenario in the Cautín river basin, located in the Araucanía region, Chile. To this end, we calibrated 20 model structures created with the FUSE hydrological modeling platform, using historical daily data available from 1979 to 2014. Runoff projections were generated using the three best-performing model structures, selected based on the Kling-Gupta using daily flows in raw and logarithmic space, with values exceeding 0.9. To evaluate meteorological and hydrological droughts, we used the Standardized Precipitation Evaporation Index (SPEI), and the Standardized Streamflow Flow (SSFI) computed for a 12-month time scale, considering five global circulation models (GCMs).

The catchment-scale precipitation is projected to decrease ~40% for the period 2051-2085 compared to the historical reference period 1979-2014, and median runoff values are expected to decrease 61% according to some GCMs. The results indicate that the duration of moderate meteorological and hydrological droughts is expected to increase by 144 months and up to 87 months, respectively. Additionally, the mean intensity of extreme meteorological droughts based on the SPEI index is projected to be 2.33, and the mean intensity of moderate hydrological droughts based on the SSFI index is projected to be 1.2, both for the 2051-2085 period.