Urban green space is increasingly viewed as essential infrastructure to build resilience to climate change by retaining water in the city landscape and balancing ecohydrological partitioning into evapotranspiration for cooling and groundwater recharge. Quantifying how different vegetation types affect water partitioning is essential for future management, but paucity of data and the complex heterogeneity of urban areas make water balance estimates challenging. Here, we provide a preliminary assessment of water partitioning from different sized patches of trees and grass as well as from sealed surfaces. To do this, we used limited field observations together with an advanced, process-based tracer-aided ecohydrological model at a meso-scale (5 km2) in central Berlin, Germany. Transpiration was the dominant green water flux accounting for over 50% of evapotranspiration in the modelled area. Green water fluxes were in general greater from trees compared with grass, but grass in large parks transpired more water compared with grass in small parks that were intensively used for recreation. Interception evaporation was larger for trees compared with grass, but soil water evaporation was greater for grass compared with trees. We also show that evapotranspiration from tree-covered areas comprise almost 80% of the total evapotranspiration from the whole model domain while making up less than 30% of the surface cover. The results form an important stepping-stone towards further upscaling over larger areas and highlights the importance of continuous high-resolution hydrological measurements in the urban landscape, as well as the need for improvements to ecohydrological models to capture important urban processes.
Bibliographical noteFunding Information:
The authors wish to thank the Einstein Foundation Berlin for financing the MOSAIC project (EVF-2018-425), in which this study was performed. MG and CM are associated with the Research Training Group ‘Urban Water Interfaces’ (UWI), GRK 2032/2 as collegiates. Contributions from CS were also funded by the Leverhulme Trust's ISOLAND project. Funding was also received through the Einstein Research Unit ‘Climate and Water under Change’ from the Einstein Foundation Berlin and Berlin University Alliance. The German Federal Ministry of Education and Research (BMBF) funded instrumentation of the Urban Climate Observatory (UCO) Berlin under grant 01LP1602 within the framework of Research for Sustainable Development (FONA; www.fona.de). The simulations were performed on the High Performance Computing cluster of TU Berlin. We acknowledge support by the German Research Foundation and the Open Access Publication Fund of TU Berlin.
Data Availability StatementPrecipitation isotopes and data on soil water content are available upon reasonable request. Precipitation data are available publicly from the Deutsche Wetterdienst (DWD). Digital elevation map, aerial phots, land use data and sealed surface data are publicly available from the Berlin Senate.
- ecohydrological modelling
- sealed surfaces
- urban green spaces
- urban hydrology
- water partitioning