Influence of vegetation on runoff and sediment in wind-water erosion crisscross region in the upper Yellow River of China

All characteristics of vegetation, runoff and sediment from 1960 to 2010 in the Xiliu Gully Watershed, which is a representative watershed in wind-water erosion crisscross region in the upper reaches of the Yellow River of China, have been analyzed in this study. Based on the remote sensing image data, and used multi-spectral interpretation method, the characteristics of vegetation variation in the Xiliu Gully Watershed have been analyzed. And the rules of precipitation, runoff and sediment's changes have been illuminated by using mathematical statistics method. What's more, the influence mechanism of vegetation on runoff and sediment has been discussed by using the data obtained from artificial rainfall simulation test. The results showed that the main vegetation type was given priority to low coverage, and the area of the low vegetation coverage type was reducing year by year. On the country, the area of the high vegetation coverage type was gradually increasing. In a word, vegetation conditions had got better improved since 2000 when the watershed management project started. The average annual precipitation of the river basin also got slightly increase in 2000-2010. The average annual runoff reduced by 37.5%, and the average annual sediment reduced by 73.9% in the same period. The results of artificial rainfall simulation tests showed that the improvement of vegetation coverage could increase not only soil infiltration but also vegetation evapotranspiration, and then made the rainfall-induced runoff production decrease. Vegetation root system could increases the resistance ability of soil to erosion, and vegetation aboveground part could reduce raindrop kinetic energy and splash soil erosion. Therefore, with the increase of vegetation coverage, the rainfall-induced sediment could decrease.