Temporal-spatial changes of soil erosion and their relation with precipitation since the project of returning farmland to forest in Guizhou Province

Since its initiation, the environmental effect of the project invested by the Chinese government, which is a major forestry ecological project for returning farmland to forest in Guizhou Province, has attracted much attention. This study attempts to clarify the temporal and spatial variation characteristics of soil erosion and their influence on distribution of precipitation on the ground, which can reflect the effect of this project and help further controlling of soil erosion. We analyze the spatial and temporal changes of amount of sediment transport, modulus of sediment transport, sediment concentration and their relationship with precipitation in Guizhou since 2000. The coefficient of variations is used as the index to measure the magnitude of the change and the Spearman correlation method is employed for analysis. Results show that the amount of sediment transport, modulus of sediment transport, and sediment concentration have a tendency to reduce since the project initiation, of which all the inter-annual amplitudes are small, but greater than that of precipitation change. From spatial differences, the average amount of sediment transport, modulus of sediment transport, and sediment concentration in the Yangtze River basin of Guizhou are larger than those in the Pearl River basin of Guizhou, whereas the interannual variations of these parameters are smaller than those in the Pearl River basin of Guizhou. The correlation of precipitation and amount of sediment transport is 0.897,indicating a close relationship. The regression equation model is y=x1.223，which shows that the environmental effects of the project are insufficient and further efforts in construction are required.