Studies On Spacial Threshold Of Soil Loss Torelance In Beijing Catchment Of Miyun Reservior

The problem of water shortage is very serious in Beijing, and water and soil loss intensified the supply and demand contradiction of water resource. Miyun reservior is the most primary water supply source in Beijing, water and soil loss in the upper reaches has important influence on ecological safety in capital area. Water and soil loss is not only the most primary and direct pollution sources, but also the carrier of other pollution. Water and soil loss in different area has different effect on water quality, and its soil loss tolerance is also different. Based on experimental research, through soil erosion prediction model, the amount of soil erosion and spacial distribution in different land-use unit was predicted in the upper reaches of Miyun reservoir, and the soil loss tolerance of different soil species with different land-use was determined on the basis of the factors such as land-use, the distance to the channel, K value, gradient and erosion modulus in this paper, expecting to uncover the influence mechanism of soil loss tolerance to Miyun reservoir, consequently, it can supply a theoretical sustainment for the water and soil conservation and water resource protection in the upper reaches of reservoir, and for the construction of clean small watershed in Beijing. The main research is about the following parts:1. Soil erosion quantitative model has experienced three phases, which is experienced statistical model, physical model and distributed model. Based on domestic interrelated research results, selecting USLE erosion prediction model, database of soil erosion model in Miyun reservoir has been constructed using GIS and RS, though analyzing natural conditions such as topography, landform, soil and vegetation, investigating and collecting the data of remote sensing , weather and many kinds of thematic maps related with erosion. In the same while, the prediction and intensity classification of soil erosion modulus were researched.2. Soil erosion in the research area was evaluated quantitatively and qualitatively using spacial analysis function of GIS, combining the method of remote sensing digital image processing. Spacial distribution of soil erosion has consanguineous relationships with land-use pattern, gradient, soil and human activities (population density), the study on spacial distribution characteristic of every factor and spacial relationship between every factor and soil erosion will help to uncover the rules of soil erosion spacial distribution.3. Different land-use patterns have different effect on the growth of soil erosion, the compositor of soil erosion rate is: unused land> garden plot >grassland>farmland>forest land. The area and rate of Soil erosion increased along with gradient. Soil erosion rate embodied the difference of soil spatial distribution: bureazom> roughness soil>cinnamon soil>alluvial soil>entisol soil>paddy soil. Soil erosion intensity presented the characteristics of nubby discontinuous distribution in spatial, which is...