## 4 Results and Discussion  
### Soil Water--Groundwater Recharge Mode Analysis  
#### 4.1.1 Soil Moisture Migration Stratification  
The data (soil volume water content and soil water potential) of the 3E profile, rainfall data, and groundwater level data were monitored from 1 January 2018 to 14 November 2020, and were used to show the dynamic changes (Figure 2) of the soil volume water content and soil water potential as they were affected by rainfall and the groundwater level over time. According to the soil volume water content dynamic change diagram (Figure 2), we were able to determine that abundant rainfall can make the soil volume water content remain at a high level all the time, except for the shallow layers during a drought period. We can see that there was an obvious stratification phenomenon within the same period, and the soil profile of the field test site can be mainly divided into zones according to this phenomenon by soil volume water content dynamic changes at different depths in profile 3E (Figure 2). The vadose zone of the field test site included the following zones: the sensitive zone of rainfall infiltration (0-1.4 m), the buffer zone of rainfall infiltration (1.4-3.5 m), and the migration zone of rainfall infiltration (3.5-5.0 m). The changing trend of the soil moisture of soil layers at 5.0 m and 6.0 m was similar to the 4.0 m and 4.5 m soil layers, with an obvious difference, but the same could be observed with the groundwater level's rising and falling. The obvious difference was mainly caused by the groundwater level, which is consistent with the previous research results [15]. Finally, we regarded the soil layer at the depths from 5.0 m to 15.0 m as the rainfall infiltration and groundwater level co-influenced zone. In order to analyze whether or not the soil moisture in the depth range of 5.0 m to 6.0 m was affected by the micro-confined groundwater level, when threshold gradient I0 and soil moisture in pores were taken into consideration, the soil moisture data (5.0 m layer and 6.0 m layer), rainfall data, and capillary zone roof elevation data (H) during the monitoring period were used to plot a dynamic change diagram (Figure 3) for analysis. Figure 3: The dynamic change diagram of rainfall, soil volume water content, and capillary zone roof elevation in profile 3E. Light blue dashed line and light orange dashed line represent the soil layer elevations at the depths of 6.0 m and 5.0 m.  
Figure 2: (**a**) The dynamic changes in rainfall, groundwater level, and soil volume water content of monitoring layers in profile 3E; (**b**) the dynamic changes in rainfall, groundwater level, and soil total water potential of monitoring layers in profile 3E. The elevations of the cohesive soil layers at the depths of 5.0 m and 6.0 m were 28.40 m (light orange dashed line in Figure 3) and 27.40 m (light blue dashed line in Figure 3). It is obvious that the elevation of the capillary zone roof (H) had broken through the monitoring soil layer at the depth of 6.0 m during three periods (from 5 July 2018 to 16 July 2018; from 3 July 2020 to 16 August 2020; from 22 September 2020 to 31 October 2020), and it even broke through the monitoring soil layer at the depth of 5.0 m on 21 July 2020 (Figure 3). This indicates that the upward movement of the capillary zone roof caused by the rise in the groundwater level can increase the soil volume water content and cause a positive correlation impact on the soil moisture of layers below the depth of 5.0 m.  
The soil volume water content at the depths of 5.0 m and 6.0 m decreased quickly during five periods (from 4 July 2018 to 11 July 2018; from 9 April 2019 to 12 April 2019; from 25 May 2019 to 8 June 2019; from 17 June 2019 to 23 June 2019; from 13 September 2020 to 7 October 2020) due to the decrease in the elevation of the capillary zone roof (H). The soil moisture decrease at the depth of 6.0 m was much greater and the response was quicker than at 5.0 m (Figure 3), which indicates that soil moisture below the depth of 5.0 m moves down to recharge groundwater.