Multi-scenario land use and soil erosion changes based on PLUS-CSLE model: case of Danjiangkou Reservoir area and its upstream watershed

The Danjiangkou Reservoir area and its upstream watershed are important strategic water sources in China. Clarifying the land use change pattern and soil erosion characteristics in this area is of great significance to ensure the water quality safety of the water source area of the South-to-North Water Diversion Middle Route Project. Based on the dynamic trends of land use and soil erosion in the Danjiangkou Reservoir area and its upstream watershed from 2010 to 2020, this study predicts the distribution patterns of land use and soil erosion in 2030 under three scenarios (ecological protection, intensive development, and natural development) using the PLUS model and the CSLE model. The results show that: ① From 2010 to 2020, the areas of forestland, grassland, and construction land increased, while cultivated land decreased by 569.19 km². The PLUS model simulation indicates that by 2030, forestland and grassland areas will slightly increase compared to 2020, construction land will continue to expand with a maximum increase of 915.25 km², and cultivated land will continue to decline by approximately 3%~4%. ② The overall soil erosion intensity in the basin showed a downward trend from 2010 to 2020, with the average soil erosion modulus decreasing from 376.03 t/(km²·a) to 251.68 t/(km²·a). However, some areas still face risks of transformation from slight to light and moderate erosion. ③ Results from the Geographical Detector indicate that topography (slope and elevation), GDP, water distribution, and vegetation cover (NDVI) are the dominant driving factors influencing the spatial distribution of soil erosion. ④ The ecological protection scenario shows the most effective soil erosion control. Under the ecological protection, intensive development, and natural development scenarios, the average soil erosion modulus in 2030 is projected to be 219.82 t/(km²·a), 244.11 t/(km²·a), and 260.73 t/(km²·a), respectively. ⑤ It is therefore recommended to strictly protect ecologically sensitive areas and promote intensive development in flat terrain zones to balance ecological security and socioeconomic development. The results provide valuable insights for maintaining ecological security, guiding soil and water conservation planning, and optimizing land use layout in the water source area of the South-to-North Water Diversion Middle Route Project.