*2.1. Study Area*

In this study, we selected the Pianguanhe River in the key soil erosion region of the Loess Plateau as our case study. The Pianguanhe River is located in the hilly and gully region of the Loess Plateau (111◦26 E–112◦17 E, 39◦15 N–39◦42 N) (Figure 1). It is a tributary of the Yellow River with a watershed area of 2089 km2, with altitude ranging from 984 to 2162 m. The study area features a semi-arid continental climate, with an average annual rainfall of 429 mm. The uneven seasonal distribution of precipitation results in more than 80.9% of the annual precipitation occurring from May to September [50]. The average annual runoff and sediment discharge is 39.48 million m3 and 12.58 million t, respectively. The sediment modulus is 65.23 t/ha/yr [50]. The overall loss of soil and water is a serious environmental issue.

**Figure 1.** Location of the study area.
