Drought propagation and ecosystem resilience in a peri-urban catchment of Berlin-Brandenburg

Abstract. Climate change intensifies pressure on water resources, making it essential to understand how drought severity affects both surface and groundwater systems and their impact on vegetation. Local studies can offer critical insights into ecosystem responses and help to support targeted adaptation strategies. This study investigates the drought dynamics and their effects on surface water, groundwater, and vegetation across the Tegeler Fliess catchment in Berlin/Brandenburg from November 2008 to April 2021. Calculating drought indices for atmospheric, hydrological and groundwater drought, namely the Standardized Precipitation Index (SPI), the Standardized Surface Water Level Index (SSWLI) and the Standardized Groundwater Level Index (SGLI), respectively, the analysis identifies station-specific drought events and their propagation across three locations: Schildow, Luebars, and Tegel. The three indices allow us to take a closer look at the differences and the propagation of drought processes over different parts of the hydrological system. The study also assesses the impact of drought on vegetation health using the Normalized Difference Vegetation Index (NDVI). Our results strongly differ at different locations: the peri-urban area (Tegel) experienced the most extreme and prolonged groundwater droughts. In contrast, groundwater in the nature reserve and fen meadow area (Schildow) experienced more moderate occurrences of drought. Thus, this area remained more resilient but faced significant surface water stress. Agricultural land (Luebars) displayed variability in both surface and groundwater responses, with surface water systems being more resilient. NDVI analysis revealed little to no observable effect with only moderate changes in vegetation throughout the study period, showing resilience despite severe drought conditions from 2018 to 2020. Spearman correlation tests did not show any significant relationship between NDVI and drought indices, while Granger causality tests revealed that SPI, and for some stations also SSWLI, significantly Granger-caused NDVI with a lag of one month. These findings highlight the need for localized drought management strategies tailored to both surface and groundwater resources, alongside enhanced vegetation monitoring that goes beyond traditional indices like NDVI.