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

• DOI: 10.3389/fclim.2023.1233536
• Publication Date: 2023-10-03T09:34:19Z
• Authors: Joël Arnault; Anthony Musili Mw...; Tanja Portele; Lu Li; Thomas Rummler; Benjamin Fersch; Mohammed Abdullah...; Titike Kassa Bahaga; Zhenyu Zhang; Eric Mensah Mortey; Ifeany Chukwudi A...; Hassane Moutahir; Souleymane Sy; Jianhui Wei; Patrick Laux; Stefan Sobolowski; Harald Kunstmann
• Keywords: Afforestation; Water cycle

Afforestation as a climate change mitigation option has been the subject of intense debate and study over last few decades, particularly in tropics where agricultural activity is expanding. However, impact such landcover changes on surface energy budget, temperature, precipitation remains unclear feedbacks between various components are difficult to resolve interpret. Contributing this scientific debate, regional models varying complexity can be used test how reacts afforestation. In study, focus gauged Nzoia basin (12,700 km 2 ) located heavily farmed region tropical Africa. A reanalysis product dynamically downscaled with coupled atmospheric-hydrological model (WRF-Hydro) finely land-atmosphere system region. To overcome problem river flooding its banks we enhance WRF-Hydro an overbank flow routing option, which improves representation daily discharge based Nash-Sutcliffe efficiency Kling-Gupta (from −2.69 0.30, −0.36 0.63, respectively). Changing grassland cropland areas savannas, woody evergreen broadleaf forest three synthetic numerical experiments allows assessment potential impacts afforestation strategies. all cases, afforestation-induced decrease soil evaporation larger than increase plant transpiration, thus increasing sensible heat flux triggering localized negative feedback process leading more runoff. This effect pronounced savannas experiment, 7% less evapotranspiration, but 13% precipitation, 8% runoff, 12% underground runoff predicted basin. demonstrates potentially large water resources, should investigated detail for policy making purposes.