Using soil water isotopes to infer the influence of contrasting urban green space on ecohydrological partitioning

Abstract. Many urban areas are facing challenges in balancing domestic and industrial water demands while simultaneously maintaining the water supply for green infrastructure. Consequently, quantitative knowledge about ecohydrological partitioning in different types of urban green space is crucial for balancing sustainable water needs in cities during future challenges of increasing urbanization and climate warming. Using isotopic tracers in precipitation and soil water, along with conventional hydrometric measurements in a plot-scale study in Berlin, Germany, we investigated water partitioning under different generic types of urban vegetation (grassland, shrub and trees). This allowed assessment of effects on subsequent evapotranspiration, subsurface flow paths and storage during a prolonged drought period with episodic rainfall. Water losses under forest were slightly higher than grassland over the monitoring in the growing season of 2019. Despite higher soil evaporation losses under urban grassland, higher interception and transpiration likely contributed to slower turnover of soil water and older groundwater recharge under urban trees. Shrub vegetation seemed to be most resilient to prolonged drought periods, with lower evapotranspiration losses. Our results contribute to a better understanding of ecohydrological partitioning under mixed urban vegetation communities and an evidence base for better adaptive management of urban water and irrigation strategies to sustainably meet the water demands of urban green spaces.