Background Soil erosion may lead to serious hazards, such as flood and land degradation and it is one of the global ecological and environmental issues. The quantitative evaluation of soil erosion at the basin scale can provide data support and reference for soil and water conservation planning and soil erosion control. At present, there are few studies on the spatial and temporal changes of soil erosion in the long time at the large watersheds scope.

Methods This study was based on the basic theory of soil erosion science and the GIS technology. Factors of influencing soil erosion in 1995, 2000, 2005, 2010 and 2015 were calculated with daily rainfall data of climate stations from 1961 to 2018, land-use data and DEM data using the methods of spatial interpolation et al. CSLE model was used to assess the spatial variations of soil erosion intensity and determine the distribution of soil erosion grade from 1995 to 2015.

Results  1) The annual mean of rainfall erosivity factor R value was between 4 275 and 5 934 MJ·mm/(hm²·h·a) in Zhengshui River Basin with high spatial heterogeneity, the average soil erodibility factor K value was 0.004 333 t·hm²·h/(hm²·MJ·mm), the average slope and slope length factor LS value was 4.45, the vegetation cover and biological practice factor B value was between 0.445 6 and 0.451 1, the engineering practice factor E value was between 0.710 9 and 0.714 3, and the tillage practice factor T value was between 0.705 6 and 0.709 5. 2) The average soil erosion modulus were 412, 520, 479, 530 and 528 t/(km²·a) respectively in 1995, 2000, 2005, 2010 and 2015. The average erosion modulus of this 5 years was 494 t/(km²·a), which belonged to the slight erosion level. 3) The modulus of soil erosion changed with elevation and the soil erosion of different land types from high to low was listed as rain fed cropland, forest land, sparse woodland and paddle field. 4) During the study period, erosive rainfall change was the main factor leading the change of the soil erosion modulus. 5) The calculated results of erosion in the control range of hydrometric station were much larger than the measured sediment. The sediment and the sediment transport ratio decreased year by year. High-coverage forests and grasses in the watershed, soil and water conservation projects participate in the process of intercepting sediment, causing most of the sediment to deposit locally or along the way, and ultimately failing to reach the sediment outlets of various hydrological stations, making the sediment delivery ratio much smaller.

Conculsions The soil erosion calculation result is bigger than the observed value of sediment in Zhengshui River Basin. The assessment soil loss value is valuable for reference. Hengyang county, Shaodong county and Hengnan county are the key areas of soil and water conservation in the future.