Regional water cycle sensitivity to afforestation: synthetic numerical experiments for tropical Africa

Frontiers in Climate

Climate

Ifeany Chukwudi Achugbu¹  Souleymane Sy²  Thomas Rummler²  Harald Kunstmann³  Joël Arnault³  Zhenyu Zhang³  Hassane Moutahir⁴  Jianhui Wei⁴  Tanja Portele⁴  Benjamin Fersch⁴  Patrick Laux⁴  Titike Kassa Bahaga⁵  Mohammed Abdullahi Hassan⁵  Stefan Sobolowski⁶  Lu Li⁶  Anthony Musili Mwanthi⁷  Eric Mensah Mortey⁸ 

[1] Department of Water Resources Management and Agrometeorology, Federal University Oye-Ekiti, Oye-Ekiti, Nigeria;WASCAL, Federal University of Technology Akure, Akure, Nigeria;Institute of Geography, University of Augsburg, Augsburg, Germany;Institute of Geography, University of Augsburg, Augsburg, Germany;Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Garmisch-Partenkirchen, Germany;Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Garmisch-Partenkirchen, Germany;Intergovernmental Authority on Development (IGAD) Climate Prediction and Applications Center, Nairobi, Kenya;Norwegian Research Center (NORCE), Bjerknes Centre for Climate Research, Bergen, Norway;University of Nairobi, Nairobi, Kenya;Intergovernmental Authority on Development (IGAD) Climate Prediction and Applications Center, Nairobi, Kenya;West African Science Service Center on Climate Change and Adapted Land Use (WASCAL), Université Abdou Moumouni, Niamey, Niger;Earth Observation Research and Innovation Centre, University of Energy and Natural Resources, Sunyani, Ghana;

关键词: regional climate modeling;    WRF-Hydro;    landcover change;    vegetation atmosphere feedback;    Nzoia basin;    East Africa;    river discharge;    water resources;   

DOI  :  10.3389/fclim.2023.1233536

 received in 2023-06-02, accepted in 2023-09-18,  发布年份 2023

来源: Frontiers

【 摘 要 】

Afforestation as a climate change mitigation option has been the subject of intense debate and study over the last few decades, particularly in the tropics where agricultural activity is expanding. However, the impact of such landcover changes on the surface energy budget, temperature, and precipitation remains unclear as feedbacks between various components are difficult to resolve and interpret. Contributing to this scientific debate, regional climate models of varying complexity can be used to test how regional climate reacts to afforestation. In this study, the focus is on the gauged Nzoia basin (12,700 km2) located in a heavily farmed region of tropical Africa. A reanalysis product is dynamically downscaled with a coupled atmospheric-hydrological model (WRF-Hydro) to finely resolve the land-atmosphere system in the Nzoia region. To overcome the problem of Nzoia river flooding over its banks we enhance WRF-Hydro with an overbank flow routing option, which improves the representation of daily discharge based on the Nash-Sutcliffe efficiency and Kling-Gupta efficiency (from −2.69 to 0.30, and −0.36 to 0.63, respectively). Changing grassland and cropland areas to savannas, woody savannas, and evergreen broadleaf forest in three synthetic numerical experiments allows the assessment of potential regional climate impacts of three afforestation strategies. In all three cases, the afforestation-induced decrease in soil evaporation is larger than the afforestation-induced increase in plant transpiration, thus increasing sensible heat flux and triggering a localized negative feedback process leading to more precipitation and more runoff. This effect is more pronounced with the woody savannas experiment, with 7% less evapotranspiration, but 13% more precipitation, 8% more surface runoff, and 12% more underground runoff predicted in the Nzoia basin. This study demonstrates a potentially large impact of afforestation on regional water resources, which should be investigated in more detail for policy making purposes.

【 授权许可】

Unknown   
Copyright © 2023 Arnault, Mwanthi, Portele, Li, Rummler, Fersch, Hassan, Bahaga, Zhang, Mortey, Achugbu, Moutahir, Sy, Wei, Laux, Sobolowski and Kunstmann.