| Gushanchuan Basin is a typical tributary of the Loess Plateau Region which located at Muddy and Coarse Sand Area. Gushanchuan Basin became one of the areas with the most intensive soil erosion in Loess Plateau Region because of the accelerated degree of soil erosion as its unique topography and climate, plus human activities that forest vegetation damagement, over-cultivation, irrational farming methods and so on. This article quantitatively evaluated the soil erosion in the study area during the past 30 years, analyzed the spatial and temporal evolution of soil and water loss with the help of remote sensing and GIS technology in order to provide data and technical support for the comprehensive management of soil and water loss for the area. The main contents of this research are as follows:(1)Building database of index used in the assessment of soil erosion: This research built up the index system for empirical sediment yield model through data collecting based on empirical soil erosion model taking Hilly-Gully Region in Loess plateau as study area. Land-use and vegetation coverage data in 1975, 1986, 1997 and 2006 were extracted from remote sensing images. Data for climate, soil characteristic and topography were also collected. The database for soil erosion assessment was built in ArcGIS based on data above with unique data format and projection.(2) Assessment and analyse on soil erosion in Gushanchuan Basin: This research accomplished the soil erosion assessment in 1975, 1986, 1997 and 2006 in Gushanchuan Basin and gave the precision analyse by contrasting with hydrological data with the support of GIS technology using USLE combined with assessment of wind erosion and gully erosion.(3) It can be concluded from the dynamic changes of soil erosion from 1975 to 2006 in Gushanchuan Basin that, the situation of soil erosion in the study area was divided into two stages: The first stage was from 1975 to 1986, the area of soil erosion increased by 138.13 km2, the percentage of soil erosion area increased to 76.80% from 65.94%. Soil erosion intensity increased in 46.69% of the area. The second stage was from 1986 to 2006. The soil erosion area decreased by 163.09km2 and the percentage of soil erosion area decreased to 63.98% from 76.80%. The erosion situation changed greatly from 1997 to 2006 during which period soil erosion area decreased by 128.19 km2 which was 49.45% of the study area. The soil erosion of the basin was better controlled till 2006.(4)The area of soil erosion above moderate degree corresponded well to the areas with high rainfall erosivity. The period of intense soil and water loss matched well with the period of active human activities. In the first stage of the study period talked above, some passive human activities such as deforest and reclamation accelerated soil erosion and resulted in more soil and water loss in this period. In the second stage, there were great achievements on soil and water conservation in Gushanchuan Basin and soil and water loss declined to some extent due to some positive human activities, particularly the implementation of returning farmland to forest project in the late stage of this period. This played a positive role in restoration of the ecological environment of the basin.
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