Groundwater Dynamics and Evapotranspiration Processes from Gobi Desert to Riparian Zone in Water-Limited Environment

Friday, 19 December 2014
Ping Wang1,2, Sergey P Pozdniakov3, Sergey Grinevsky3, Guo-Yue Niu2, Jingjie Yu1 and Chaoyang Du1, (1)IGSNRR Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing, China, (2)University of Arizona, Tucson, AZ, United States, (3)Moscow State University, Moscow, Russia
Evapotranspiration (ET) including evaporation from soil surfaces and transpiration through plants’ stomata exerts dominant controls on shallow groundwater dynamics under hyper-arid climates. Our analyses of diurnal and seasonal groundwater dynamics at desert sites in northwestern China for the period 2010-2014 showed that different patterns of groundwater dynamics in a Gobi-desert and riparian zones are highly related to ET processes. To quantify ET in the hyper-arid climates, we developed diagnostic indicators of the groundwater-ET relationship and a methodology based on seasonal groundwater level fluctuation approach. Under similar climates and depth to the water table (2-2.5 m), ET in the riparian zones as a result of direct root water uptake (RWU) through riparian shrubs (0.63-0.73 mm/d at the Tamarix ramosissima site and 1.89-2.33 mm/d at the Populus euphratica site) is much greater than that in a Gobi-desert site (0.12-0.27 mm/d). Numerical simulations using a one-dimensional land surface model with a RWU model that explicitly describes root-groundwater interactions indicate that direct RWU at the riparian sites is primarily dependent on the root dynamics that interacts with groundwater dynamics.