## 3 Results and Discussion
### Soil Water Change in Slopes under Natural Evaporation Conditions
#### 3.3.3 Soil Water Dissipation Law of Vegetated Slopes under Natural Evaporation Conditions  
The dissipation of soil water at varying depths of vegetated slopes with several slope ratios over the course of 14 days is presented in Figure 14. From the figure, it is evident that on the first day after the rainfall ceased, the soil water dissipation at depths of 20 cm, 40 cm, and 60 cm in slopes with a slope ratio of 1:1.5 was 2.1%, 1.6%, and 1.1%, respectively. For slopes with a slope ratio of 1:1.75, the soil water dissipation at each depth was 2.4%, 2.0%, and 1.3%, respectively. Similarly, for slopes with a slope ratio of 1:2, the soil water dissipation at each depth was 2.7%, 2.3%, and 1.2%, respectively. These results indicate that higher slope ratios in vegetated slopes lead to lower soil water dissipation within the first day after the end of the rainfall. After 14 days of natural evaporation following rainfall, the soil water dissipation at depths of 20 cm, 40 cm, and 60 cm in slopes with a slope ratio of 1:1.5 was 8.9%, 6.0%, and 2.4%, respectively. For slopes with a slope ratio of 1:1.75, the soil water dissipation at each depth was 6.3%, 4.7%, and 2.2%, respectively. Similarly, for slopes with a slope ratio of 1:2, the soil water dissipation at each depth was 5.0%, 4.0%, and 2.2%, respectively. At a depth of 100 cm in the vegetated slope, the soil water content remained relatively stable over 14 days, with only minimal water dissipation of 0.1%. These findings highlight that soil water dissipation at depths of 20 cm and 40 cm in the vegetated slope is significantly influenced by the slope ratio. A higher slope ratio corresponds to greater soil water dissipation within the 40 cm range. However, there were no notable differences in soil water dissipation between the depths of 60 cm and 100 cm in vegetated slopes with varying slopes.  
Figure 14: Soil water dissipation from vegetated slopes with different slope ratios and how it changes with time: (**a**) slope ratio of 1:1.5, (**b**) slope ratio of 1:1.75, (**c**) slope ratio of 1:2.  
Figure 13: Soil water dissipation from bare slopes with different slope ratios and how it changes with time: (**a**) slope ratio of 1:1.5, (**b**) slope ratio of 1:1.75, (**c**) slope ratio of 1:2.  
The trend of soil water dissipation in vegetated slopes over time shows that the rate of soil water dissipation gradually decreases at each depth after rainfall. It is observed that the soil water dissipation rate is faster in shallower depths compared to deeper depths. At a depth of 20 cm, soil water dissipation is similar to that at a depth of 40 cm but significantly different from that at a depth of 60 cm. This law can be attributed to water absorption by plant roots. In order to support its growth and development, vegetation reduces the soil water content of the slope through root absorption and transpiration within its root zone. Consequently, there is a significant decrease in soil water content at depths of 20 cm and 40 cm. As the soil water content decreases in the shallow soil, water from the 60 cm soil layer slowly migrates towards the slope surface to replenish the water content in the shallow soil. As a result, the rate of soil water dissipation at a depth of 60 cm is slower and the amount of dissipation is also lower. When the depth of vegetated slopes is less than 40 cm, water dissipation is significantly higher compared to bare slopes. However, when the depth is greater than 60 cm, it is less than that of the bare slope.