The 2018–2023 drought in Berlin: impacts and analysis of the perspective of water resources management

Abstract. The years 2018 to 2023 were characterised by extreme hydrometeorological conditions, with record-high average annual air temperatures and record-low annual precipitation across large regions of Europe. Berlin, the capital of Germany, is potentially vulnerable to drought conditions due to its location in a relatively dry region with relatively high water demand and complex water resources management in the Spree and Obere Havel catchments. To address the impacts of the 2018–2023 drought, various water resources management measures were implemented in Berlin and in the Spree and Obere Havel catchments. As a case study of how droughts impact large cities, we analysed observed and modelled time series of hydrometeorological, hydrogeological, and hydrological variables in Berlin and the Spree and Obere Havel catchments to characterise the years 2018–2023 in comparison with long-term averages. We found that the meteorological drought propagated into soil moisture drought and hydrological drought, e.g. in terms of record-low groundwater and surface water levels and streamflow, with smaller rivers drying up. Due to the intensity and duration of the drought, water resources management was only able to partially counteract the drought situation, so water use was partially limited, e.g. in terms of shipping. Enhanced proportions of sewage water and reverse flow were associated with detectable concentrations of trace substances. However, Berlin's water supply was always guaranteed and represents a stable system. Climate change is expected to lead to more frequent meteorological droughts, which will have more severe hydrological impacts in the future due to socioeconomic changes in Berlin (increasing population) and the catchments (termination of mining discharges). Therefore, water resources management in Berlin and in the Spree and Obere Havel catchments needs to be adapted to combat such situations, taking into account the lessons learned from the 2018–2023 drought and possible future developments. This integrative and multidisciplinary study can help better assess drought impacts in the Berlin–Brandenburg region and guide water management planning under potentially drier conditions. We suggest that the integrative approach presented here can be transferred and adapted to study drought impacts on other large cities.