Fig 1.
Location map of the Qin River watershed.
DEM was obtained from National Tibetan Plateau Data Center (http://data.tpdc.ac.cn). Reprinted from http://data.tpdc.ac.cn under a CC BY 4.0 license, with permission from National Tibetan Plateau Data Center, original copyright [2019]. The national boundary was obtained from Natural Earth (http://www.naturalearthdata.com/). The scope of the Qin River Basin was determined based on DEM and eight-direction (D8) algorithm. Based on authors’ field investigation, we have modified and adjusted the vector boundary.
Table 1.
Sources of datasets used in this study.
Fig 2.
Flow chart of methodology.
Table 2.
Assignment of P values based on land use.
Fig 3.
Soil erosion in 1990 (a); soil erosion in 2000 (b); soil erosion in 2010 (c); soil erosion in 2018 (d). According to Formula 1, we multiply the six factors R, K, L, S, C and P in ArcGIS 10.2 software to obtain soil erosion maps in 1990, 2000, 2010 and 2018. The scope of the Qin River Basin was determined based on DEM and eight-direction (D8) algorithm. Based on authors’ field investigation, we have modified and adjusted the vector boundary.
Table 3.
Soil erosion severity class areal distribution from 1990 to 2018.
Fig 4.
Distribution of the soil-erosion intensity of different land-use types for Qin River Basin.
We used ArcGIS software to extract the areas of cultivated land, forest land and grassland, and superimposed soil erosion with the extracted areas to obtain the distribution map of soil erosion intensity for different land uses. The scope of the Qin River Basin was determined based on DEM and eight-direction (D8) algorithm. Based on authors’ field investigation, we have modified and adjusted the vector boundary.
Table 4.
Spatiotemporal changes in soil erosion for land-use patterns from 1990 to 2018.
Table 5.
Soil erosion proportions of different land-use types in the Qin River Basin (%).
Fig 5.
Distribution of the intensity of soil erosion at regions with varying slopes in the Qin River Basin.
Slop≤5°(a); 5°<Slop<8°(b); 8°≤Slop≤15°(c); 15°≤Slop<25°(d); 25°≤Slop<35°(e); Slop≥35°(f). Based on the superposition analysis function of the ArcGIS software, we extracted the slopes of the Qin River Basin, and divided them into 6 categories according to the gradient classification standards. The six types of slope maps and soil erosion maps were masked to obtain soil erosion classification maps of different slopes. The scope of the Qin River Basin was determined based on DEM and eight-direction (D8) algorithm. Based on authors’ field investigation, we have modified and adjusted the vector boundary.
Table 6.
Soil erosion intensity under different slopes.
Table 7.
Areas of varying intensities of soil erosion based on slope (%).
Fig 6.
Distribution of the soil-erosion intensity at different altitudes.
Altitude≤200m(a); 200m<Altitude≤500m(b); 500m<Altitude≤800m(c); 800m<Altitude≤1200m(d); 1200m<Altitude≤1500m(e); Altitude>1500m(f). According to reference 62, we divided the Qin River Basin into six grades, using the spatial analysis function of ArcGIS software to extract the area at different altitudes, and using the mask extraction function to obtain the soil erosion degree maps at different altitudes. The scope of the Qin River Basin was determined based on DEM and eight-direction (D8) algorithm. Based on authors’ field investigation, we have modified and adjusted the vector boundary.
Table 8.
Soil erosion at different altitudes.
Table 9.
Proportion of areas (%) with varying intensities of soil erosion at different altitude ranges.