Spatial-Temporal Variation of Runoff Erosivity in Karst Basin and Its Response to Karst Characteristic Factors

[Objective] The soil erosion issue is very prominent in the karst region of southwest China and significantly affects the sustainable development of the regional economy. However, it is currently not very clear how the characteristic environmental factors of karst basins affect the direct driving force of soil erosion and runoff erosivity. [Methods] Taking the Yeji River Basin in the karst region of southwest China as an example and basing on the long-term and high-frequency field measurement data at the outlet hydrological station of the basin, the spatiotemporal change characteristics of runoff erosivity from 2005 to 2020 were evaluated and the influence of main karst environmental factors on runoff erosivity was analyzed by the Soil and Water Assessment Tool (SWAT) and the Partial Least Squares Model (PLSR). [Results] The average annual runoff erosivity was 2 326.47 m4/(km2·s), with strong spatial heterogeneity. In 2005, the high runoff erosivity was mainly distributed in the northern and central parts of the basin. During 2010—2020, the high runoff erosivity area gradually shifted to the central and southern parts of the basin. In terms of time, benefiting from the implementation of ecological restoration projects such as comprehensive control of soil and water loss in sloping farmland and comprehensive control of rocky desertification since the 11th Five-Year Plan, the runoff erosivity of the Yeji River Basin had been generally decreasing year by year. Lithology, exposed bedrock, and slope were the dominant control factors, which jointly explained 57.7% of the spatiotemporal variation of runoff erosivity in the Yeji River Basin. [Conclusion] These results can provide a theoretical reference for the comprehensive control of soil erosion in karst basins and help to formulate more precise and effective policies and measures to improve the ecological environment of the karst area and promote the sustainable development of the region.