Study On Soil Erosion Of Three River Source Region Based On Erosion Model And Nuclide Tracer Technique

Located in the hinterland of the Qinghai-Tibet Plateau,three river source region is the source of the Yangtze River,Yellow River and Lancang River.It has a profound impact on China’s climate and meteorological conditions,plays an important role in protecting the ecological environment in China,and even has an important impact on the climate of Asia and the world.Research on soil erosion in the three river source region is of great significance to the protection of the ecological environment of the Qinghai-Tibet Plateau and the improvement of regional sustainable development.Based on the meteorological data,soil data source area,as well as remote sensing image data,such as using RUSLE model,RWEQ model and freezing-thawing hierarchical evaluation model in Arc GIS software of three water erosion,wind erosion and freeze-thaw erosion were simulated,respectively estimated hydraulic erosion,wind erosion intensity distribution of three rivers and freeze-thaw erosion intensity distribution,and on the basis of the corresponding classification standard for all kinds of erosion intensity classification,quantitative analysis to three three spatial distribution characteristi Cs of erosion.In this study,a field survey was carried out in the source area of the three river source region,and suitable samples were selected to collect soil.The ¹³⁷Cs tracer technology was used to quantitatively calculate soil erosion in the resource region.By comparing the measured erosion results with the model estimation results,the main conclusions are as follows:（1）The overall distribution area of hydraulic erosion in the three river source region is small.The areas where the hydraulic erosion occurs are mainly distributed in the central and southern part of the resource region and the northeast part of the resource region,and the erosion is mostly dispersed and occupies a small area.In the three river source region,the most widely distributed water erosion is the slight erosion,which occupies 20.9×10⁴km²,accounting for 48.04%of the total area of the resource region.The second is light erosion,which occupies 12.73×10⁴km²,accounting for 29.27%of the total area of the resource region.The distribution of moderate and above erosion is relatively small,and the proportion of moderate erosion（3.92×10⁴km²）,extreme intensity erosion（2.25×10⁴km²）and intensity erosion（2.18×10⁴km²）is 3.92%,2.25%and 2.18%.The least distributed area is severe erosion,with an area of 1.52×10⁴km²,accounting for only 3.49%of the total area of the resource region.（2）The area of wind erosion in the three river source basin is relatively small,the wind erosion intensity in most areas is slight erosion and light erosion,while in a few areas,the wind erosion intensity is intense erosion and very strong erosion.Wind erosion is mainly distributed in the west and northeast of the resource region,and the erosion is mostly dispersed and occupies a small area.Wind erosion is the most widely distributed in the three river resource region,which covers an area of 38.45×10⁴km²and 40.29×10⁴km²respectively,accounting for 38.45%and 40.29%of the total area of the source region.The second is moderate erosion,which occupies 13.11×10⁴km²,accounting for 13.11%of the total area of the resource region.The area of the resource region is 4.54×10⁴km²and 3.61×10⁴km²,accounting for 1.97%and1.57%of the total area of the resource region,respectively.（3）The overall freeze-thaw erosion area in the three river resource region is wide,and the freeze-thaw intensity in the whole resource region is between 1.63 and 4.44.The erosion intensity of Yushu County and Nangqian County in the middle of the resource region and the eastern part of the resource region is relatively high.However,the intensity of freeze-thaw erosion near Zadoo County in the west and Maduo County in the middle of the resource region is relatively low.The most extensive freeze-thaw erosion is moderate erosion,which covers an area of 136000 km²,accounting for 38.12%of the total area of the source region.The area of the resource region is 6.07×10⁴km²and 6.56×10⁴km²respectively,accounting for 7.99%and7.40%of the total area of the resource region.The area of the resource region is 4.06×10⁴km²and 5.39×10⁴km²,accounting for 11.39%and 15.11%of the total area of the resource region,respectively.（4）The main erosion of the three river resource region is freeze-thaw erosion,with an erosion area of 25.61×10⁴km²,accounting for 58.87%.The freeze-thaw erosion is mainly concentrated in the west of the resource region.The erosion area is5.32×10⁴km²and 6.51×10⁴km²respectively,accounting for 12.24%and 14.96%of the total area.The two erosion areas are mainly concentrated in the eastern and Central South of the resource region.The distribution area of wind single-phase erosion area,water freeze-thaw and wind freeze-thaw two-phase erosion area and water wind freeze-thaw three-phase erosion area is less,accounting for about 1-2×10⁴km²,mainly distributed in the north and middle of the resource region.The distribution of erosion area in the resource region has a certain vertical difference.The high altitude area is mainly distributed in freeze-thaw erosion area,and the low altitude area is mainly distributed in two-phase and three-phase compound erosion area.Except the freeze-thaw erosion area,the other erosion areas are distributed in the form of aggregation and scatter.The freeze-thaw erosion and compound erosion are the main erosion types in the three river resource region.（5）The ¹³⁷Cs intensity of different sites in the alpine steppe of the three river resource region,ranging from 678.62 bq·m^-2to 16059.21 bq·m^-2,and the erosion modulus ranged from 1210.68 t/（km²·a）to 11045.06 t/（km²·a）.Most of the samples had moderate or above erosion,a few samples had less than moderate erosion,and a few samples had no erosion and accumulated.¹³⁷Cs intensity ranged from 374.33bq·m^-2to 15084 bq·m^-2,and erosion modulus ranged from 70.13 t/（km²·a）to12680.68 t/（km²·a）.Most of the samples had less than moderate erosion,a few samples had no erosion but accumulated,and a few samples had more than moderate erosion.Soil erosion in three river resource region is not only affected by vegetation coverage,but also by other factors.Comparing the measured results with the model simulation results,it can be proved that the model used in this paper has certain applicability.