Erosion Evolution in the Source Regions of the Yangtze and Yellow Rivers From a Climate-Ecology-Hydrology Zoning Perspective

Abstract

Combining soil erosion with comprehensive zoning can reflect the spatial differentiation of soil erosion and reveal the driving forces behind changes in soil erosion. Here, the Köppen climate classification and K-means unsupervised clustering analysis were used to categorise the source regions of the Yangtze and Yellow Rivers (SRYYR) into eight integrated climate-ecology-hydrology zones, considering vegetation, climate, runoff, and sediment transport. The CSLE model was used to analyse soil erosion rate evolution patterns and the impacts of extreme rainfall events in each zone. The study found that the eastern source of the Yangtze River and the northern source of the Yellow River experienced severe erosion. Vegetation and biological practices in the Yellow River source region were significantly better than that of the Yangtze River. Rainfall erosivity increased from northwest to southeast. Extreme rainfall can lead to a 3.86-fold difference in rainfall erosivity, and the annual distribution of rainfall significantly affects soil erosion rates. There were significant spatial differences and trends in soil erosion rates across different regions, with the central part of SRYYR still undergoing significant degradation. Conservation measures resulted in a 26.15% decrease in the B factor (vegetation and biological practice factor) in Zones II, V, VI, and VII, but the current state of vegetation cover in Zone VIII remains a concern (increase 9.23%). The condition of grassland erosion in the SRYYR region improved year by year, while arable land experienced a worsening trend, and the soil erosion rates in forests fluctuated within a certain range. The formation of erosion channels and sediment transport not only changes the landscape but also has profound impacts on water quality and downstream ecosystems.