Influence of landscape heterogeneity on water available to tropical forests in an Amazonian catchment and implications for modeling drought response. Issue 16 (18th August 2017)

• Record Type: Journal Article
• Authors: Fang, Yilin; Leung, L. Ruby; Duan, Zhuoran; Wigmosta, Mark S.; Maxwell, Reed M.; Chambers, Jeffrey Q.; Tomasella, Javier
• Is Part Of: Journal of geophysical research. Volume 122:Issue 16(2017)
• Page Start: 8410
• Page End: 8426
• Publication Date: 2017-08-18
• Subjects: landscape heterogeneity -- lateral transport of soil moisture -- transpiration -- seasonal variability of groundwater dynamics and runoff; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2017JD027066
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: The Amazon basin has experienced periodic droughts in the past, and intense and frequent droughts are predicted in the future. Landscape heterogeneity could play an important role in how tropical forests respond to drought by influencing water available to plants. Using the one‐dimensional ACME Land Model and the three‐dimensional ParFlow variably saturated flow model, numerical experiments were performed for a catchment in central Amazon to elucidate processes that influence water available for plant use and provide insights for improving Earth system models. Results from ParFlow show that topography has a dominant influence on groundwater table and runoff through lateral flow. Without any representations of lateral processes, ALM simulates very different seasonal variations in groundwater table and runoff compared to ParFlow even if it is able to reproduce the long‐term spatial average groundwater table of ParFlow through simple parameter calibration. In the ParFlow simulations, even in the plateau with much deeper water table depth during the dry season in the drought year of 2005, plant transpiration is not water stressed as the soil saturation is still sufficient for the stomata to be fully open based on the empirical wilting formulation in the models. This finding is insensitive to uncertainty in atmospheric forcing and soil parameters, but the empirical wilting formulation is an important factor that should be addressed using observations and modeling of coupled plant hydraulics‐soil hydrology processes in future studies. The results could be applicable to other catchments in the Amazon basin with similar seasonal variability and hydrologic regimes. Key Points: Landscape heterogeneity has large influences on spatial hydrologic variability at Asu Lateral transport of soil moisture modulates the seasonal variability of groundwater dynamics and runoff Transpiration at the Asu catchment is not water limited in dry season in model simulations