Evaluation of the effects of climatic variabilities on future hydrological scenarios: application to a coastal basin in Central Chile

Evaluating the impacts of climate change on coastal basins with a Mediterranean climate represents a significant challenge concerning water security. Consequently, an assessment was conducted on the effects of climate change on hydrological components in a basin within the Coastal Mountain Range of Central Chile. The hydrological model SWAT+ was used, forced by two Shared Socioeconomic Pathways (SSP2-4.5 and SSP5-8.5), incorporating a downscaling process and analyzing both extreme and non-extreme events. Climate projections were made for the following three periods: near (2015–2030), middle (2015–2060), and distant (2015–2100) future. Results indicate a consistent rise in average temperatures across all periods, coupled with decreased precipitation for most of the year. Particularly in the distant future, austral summer stands out as the most impacted season, with projections showing a substantial decrease in precipitation (27 and 54% for SSP2-4.5 and SSP5-8.5, respectively), accompanied by significant increases in both maximum and minimum temperatures. Moreover, the streamflow is anticipated to decline considerably in the austral autumn (−8 and −83% for SSP2-4.5 and SSP5-8.5, respectively). Additionally, as consequences of climate change an increase in droughts (during the dry season) and flooding problems (during the wet season) are expected in the basin, increasing the risk for both extremes.