Abstract: Moisture migration including precipitation,irrigation infiltration and evaporation from phreatic water in vadose zone plays an important role in groundwater circulation.In order to accurately evaluate the water exchange quantity through the vadose zone in Weining Plain,two in situ experiment sites were set in Zhongwei County and Zhongning County,Ningxia Hui Autonomous Region,China in this study.The observation was conducted from Jun 2013 to Nov 2013 and from Apr 2014 to Oct 2014 respectively.The soil water pressure,soil temperature,soil texture and soil hydraulic parameters at different depths were measured.The evapotranspiration,infiltration at the land surface and the evaporation,infiltration on the groundwater table were calculated using the oriented flux method.At Zhongwei experiment site,the groundwater recharge through the vadose zone in maize land which was 373.65 mm is much greater than that in eggplant land which was 152.3 mm,with the irrigation pattern in maize land being low frequency with large amount of water each time (150 mm),and the irrigation pattern in the eggplant land being high frequency with small amount of water each time (50 mm).It indicates that under the condition of the same soil texture,the same irrigation period (July to October) and the similar total irrigation amount,the irrigation pattern of crops determines the recharge quantity to the phreatic water.At Zhongning experiment site,the groundwater net recharge through the vadose zone was 32.88 mm from Jul to Oct in 2013 and 57.42 mm during the same period in 2014.It indicates that under the condition of the same soil texture,the same crop,and the same irrigation pattern,the change of the groundwater net recharge through the vadose zone is little.Under the rainfall or small amount of flooding irrigation (50 mm）the vegetation in growth will hinder the water from being infiltrated into the vadose zone,but it accelerates the infiltration of water in the case of large irrigation volume (100-150 mm）.

Key words: Weining Plain, vadose zone, moisture migration characteristics