Figure 3. Soil erosion modulus estimated by the CSLE in Jiuyuangou watershed for 2010, 2015, and 2020
Table 1 shows that the soil erosion grades in the basin from 2010 to 2020 are mainly weak erosion and slight erosion, accounting for 88.17–90.28% of the total area of the watershed. Notably, the severe erosion area only accounts for 0.62–1.46% of the total area, with the erosion area below slight following an increasing then decreasing trend and the severe erosion area following a decreasing then increasing trend from 2010 to 2020. Using the soil erosion area transfer matrix (Table 2), the dark color marks the area that remained unchanged in different soil erosion grades from 2010 to 2020: 4407.47 ha below moderate erosion, with only 13.7 ha above intensive erosion. From 2010 to 2020, 38.04 ha of the watershed area changed from severe to below moderate erosion, while only 1.62 ha changed from severe to intensive erosion. In addition, 77.83 ha of the watershed area changed from below moderate to severe erosion, while only 19.2 ha changed from intensive and very intensive to severe erosion.
Table 1. Statistics of soil erosion grade area in different years in Jiuyuangou watershed from 2010 to 2020.