| This thesis tried to discover pattern optimum of land utilization and vegetation optimum for loess plateau in Yanhe River drainage area, by analyzing the data about Yanhe River drainage area collected in the past ten years and studying the impact of rainfall on soil moisture content and on runoff in this area. The main conclusions are as following:(1) It is found through the correlation analysis of rainfall in loess plateau and soil moisture content that with increase of the depth of soil the impact of rainfall on the soil moisture content decreases. The rainfall has significant effect on soil moisture content in the depth of 0-30cm while has little effect when the depth is over 30cm.(2) By studying the impact of rainfall on the soil moisture content for land in different usages it can be concluded that the mode of utilization has significant effect on soil moisture content. Among all the land utilization mode, farming land, grassland, woodland and fish scale pit are found to bring better water conservancy in loess plateau.(3) By studying the rainfall on soil moisture content for different vegetations, it is found that the type of vegetation has noticeable effect on soil moisture content. The vegetation of Chinese pine, melon, and horizontal ditch soybean will bring better water conservancy with higher soil moisture content.(4) By studying the impact of rainfall on runoff in different lands it is found that the utilization has significant effect on runoff, with fish scale pit most effective, horizontal ditch second, waste slope third, strip cropping and farming land the least.(5) By studying the correlation analysis of multi factors, it is found that rainfall intensity has greatest effect on erosion followed by rainfall and slope gradient, and with vegetation coverage the least, which also contributes a little to erosion. |
