Study On Characteristics Of Soil And Water Loss Based On Lithological Difference In Karst Area

Based on data of hydrology geological?DEM?landuse?soil?rainfall and NDVI data,a study of soil erosion was sent in the Catchment of Sanchahe,which located in Guizhou Province,where there is a typical karst area.We calculate soil erosion modulus of Sanchahe area by using GIS and RUSLE Model,and then analyzing the rules of the spatial distribution and what impact factor lead to this consequence.Meanwhile,we analyzed the characteristic of lithology in Sanchahe area and then classified those into three types.Besides,we also conducted a fingerprint tracer experiment in Dahe area which is the sub-basins of Sanchahe area to calculate the relative contribution rate of different types soil coming from different lithology.And,Based on the results of sediment fingerprint tracer experiment,we analyzed the driving factor of soil erosion under different lithology.Finally,we can use the experiment's consequence compare with soil erosion modulus that was calculated through RUSLE model to determine if the RUSLE model is applicative in Dahe area.All of the conclusion be list as follows:1.According to the result of RUSLE model calculated,with the standard(SL190-96)for classification of soil erosion issued by the ministry of water resources,56.92% of the land in the Sanchahe basin belongs to mild erosion degree,33.34% belongs to slight erosion degree,and the area with moderate erosion degree or above accounts for less than 1%,which is against the facts.2.The distribution of soil erosion modulus calculated by RUSLE model has obvious correlation with land use type,slope,elevation in the Sanchahe basin,but has poor correlation with lithology,which is contrary to previous qualitative analysis.3.The results of fingerprint tracing show that the relative sediment contribution rate of the sand shale,which is 45.40%,in the Dahe basin is the highest,followed by the basalt,which is 39.10%,and the carbonate rock is lowest,which is 15.80%,and that the lithologic background plays an important role in suspended sediment transport.4.The RUSLE model does not take into account the effect of lithology in the karst area,and there is great uncertainty in calculating the soil erosion modulus and evaluating the erosion degree in the karst area with RUSLE model.