Deep soil water recharge response to precipitation in Mu Us Sandy Land of China

Soil water is the main form of water in desert areas, and its primary source is precipitation, which has a vital impact on the changes in soil moisture and plays an important role in deep soil water recharge (DSWR) in sandy areas. This study investigated the soil water response of mobile sand dunes to precipitation in a semi-arid sandy area of China. Precipitation and soil moisture sensors were used to simultaneously monitor the precipitation and the soil water content (SWC) dynamics of the upper 200-cm soil layer of mobile sand dunes located at the northeastern edge of the Mu Us Sandy Land of China in 2013. The data were used to analyze the characteristics of SWC, infiltration, and eventually DSWR. The results show that the accumulated precipitation (494 mm) from April 1 to November 1 of 2013 significantly influenced SWC at soil depths of 0-200 cm. When SWC in the upper 200-cm soil layer was relatively low (6.49%), the wetting front associated with 53.8 mm of accumulated precipitation could reach the 200-cm deep soil layer. When the SWC of the upper 200-cm soil layer was relatively high (10.22%), the wetting front associated with the 24.2 mm of accumulated precipitation could reach the upper 200-cm deep soil layer. Of the accumulated 494-mm precipitation in 2013, 103.2 mm of precipitation eventually became DSWR, accounting for 20.9% of the precipitation of that year. The annual soil moisture increase was 54.26 mm in 2013. Accurate calculation of DSWR will have important theoretical and practical significance for desert water resources assessment and ecological construction.