Abstract

--- - The Salar de Atacama Basin, in northern Chile, is located in one of the driest regions on Earth; its hydrological system depends heavily on high-altitude precipitation, making it highly sensitive to climate variability. However, existing studies have relied on short records or lack spatially explicit drought assessments, limiting the understanding of how precipitation decline and rising temperatures interact across different sectors of the basin. Spatiotemporal dynamics of drought in the basin were analyzed over 1990-2024 using the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI). Mean monthly temperature and precipitation data from 20 meteorological stations were combined with ERA5-Land satellite products and corrected using random forest and kriging techniques to generate bias-adjusted monthly climate rasters. The indices were computed at the pixel level and analyzed using both long-term trends and 5-year interval classifications. The results showed a progressive intensification of aridity, with SPI undergoing a statistically significant increase in the moderate drought class and a reduction in the normal drought class, indicating declining precipitation levels. Since 2010, droughts in the region have predominantly exhibited a hydroclimatic state, peaking between 2020 and 2024 when up to 80% of the basin experienced drought. The SPEI revealed a broader spatial extent of drought due to increasing temperatures and evapotranspiration, although long-term trends were less pronounced. Mild and moderate droughts were the most frequent and spatially extensive, particularly in the headwater and salt flat surface zones, where water availability was critical for aquifer recharge and local supply. - "[GRAPHICS]"