Background The upper reaches of Beiluo River watershed, located in the hinterland of the Loess Plateau, is one of the main source districts of coarse sediment of the middle Yellow River, and is also the key area for soil erosion control and ecological construction in China. The Grain for Green (GFG) project implemented in 1999, resulting in soil erosion process in the upper reaches of Beiluo River watershed changing greatly. Clarifying soil erosion changes and driving factors in the upper reaches of Beiluo River watershed before and after the GFG project is of great significance for promoting green development and health management of the Yellow River watershed.

Methods The revised universal soil loss equation was combined with GIS spatial analysis to study the spatial and temporal characteristics of soil erosion, rainfall erosivity and vegetation coverage before and after the GFG project (1991-2000 and 2001-2010) in the upper reaches of Beiluo River watershed. And the contribution rates of the GFG project and precipitation change on soil erosion change in the watershed were analyzed.

Results 1) The results showed that the mean annual rainfall erosivity decreased from 1 390.2 MJ·mm/(hm²·h·a) before the GFG project to 1 260.7 MJ·mm/(hm²·h·a) after the GFG project, a decrease of 9.3%. Rainfall erosivity decreased in 99.3% of the whole watershed. The decrease of rainfall erosivity reduced the intensity of soil erosion in the watershed. 2) The vegetation coverage of the watershed increased from 30.8% before the GFG project to 47.6% after the GFG project, with an increase of 54.5%. About 88.3% of the area showed an increasing trend of vegetation coverage. The vegetation coverage in Wuqi county of the southeast was significantly higher than that in Dingbian county of the northwest. The increase of vegetation coverage greatly weakened the intensity of soil erosion in the watershed. The combined effect of the GFG project and the change in precipitation resulted in soil loss decreased from 8 078.9 t/(km²·a) before the GFG project to 3 060.7 t/(km²·a) after the GFG project, with a decrease of 62.1%. 3) The contribution rate of the GFG project and precipitation change to reducing soil erosion in the watershed was 85% and 15% respectively. The contribution rate of the GFG project to reducing soil erosion in Wuqi county and Dingbian county was 86% and 82% respectively.

Conclusions The degree of soil erosion reduction in the watershed is dominated by the GFG project characterized by vegetation coverage change. The results provide valuable data for evaluating the benefits of soil and water conservation of ecological restoration on the Loess Plateau.