The main soil type in the watershed is loess according to the Chinese soil classification system in 1995. The loess area accounts for 65.5% of the total soil area, following by 25.1% of Red Soil and Two Coloured Soils. Soil mechanical composition includes clay (<0.002 mm, 53.9–74.8%, silt (0.002~0.05 mm, 16–26%), and sand (0.05~2 mm, 5.88–31.8%)36. Soil has a uniform texture, with low organic matter content (6.82–34.6 g/kg) and loose structure, and can be easily dispersed and transported (Fig. 2). Before watershed governance, the watershed had sparse vegetation, high planting rates and serious soil erosion37. The mean sediment yield modulus for many years was ≤14 000 t/(km2•a). Since integrated basin management started in 1997, the watershed was vegetated by afforestation and grass planting38.Figure 2Gully erosion of slope surface (a) and flat arable land (b) in Ansai County of the Yanhe River Basin in 2013 (The pictures were taken by Lei Wu in Ansai County in November 2013).