Assessing temporal trends of soil erosion and sediment redistribution in the Hexi Corridor region using the integrated RUSLE-TLSD model

Abstract

Accurately evaluating soil water-erosion dynamics and drivers is crucial for mitigating soil and water loss. To simulate the potential or net soil erosion process in China’s Hexi region (a 2.3 × 105 km2 area including three river basins), this study attempted to integrate the transport limited sediment delivery (TLSD) function within the revised universal soil loss equation (RUSLE) model (the spatial resolution of the maps was 90 × 90 m). A geographically weighted regression model was used to evaluate the contribution of influencing factors to the net water-erosion rate and the soil and water conservation benefits of the “Grain to Green Program” (GTGP) (The area proportion of land types in 2015: 6.84% (cultivated land), 3.48% (forest land), 21.68% (grassland), 66.69% (unused land), 0.75% (water), and 0.56% (construction land). The results revealed that the RUSLE-TLSD model could reliably simulate the soil erosion process in Hexi (the Nash-Sutcliffe model efficiency coefficient exceeded 0.602). The potential water erosion rate was between 6.24 and 31.01 t/ha/a from 1982 to 2015, and the net water erosion rate declined slightly, with a slope of −0.0029. Water erosion was severe in high-altitude areas (altitude > 3306 m) with slopes of more than 21° and annual precipitation above 235 mm and weak in low-altitude areas (altitude <1920 m) with slopes less than 4° and annual precipitation below 114 mm. Nearly 10% of the Qilian Mountain National Nature Reserve (QMNNR) areas experienced intensive erosion, and nearly 29% of the QMNNR areas experienced sediment deposition. Slope was the primary factor affecting soil erosion. Extreme precipitation directly aggravated the water-erosion risk, and this factor should be given increased attention particularly in arid and semi-arid regions. The GTGP effectively reduced water soil erosion caused by extreme precipitation and improved water retention and soil consolidation in Hexi.