Land Use/Cover Type Of Karst Surface In Changhe River Basin And Impacts On CN Value

In recent years, with the development of the research on global change,researches of land use/cover type develop rapidly. A series of phased research resultson land use have appeared, which become the global change research hotspot. Landuse research rose up to a new stage, since its understanding and research methodshave made significant breakthrough. As to the Karst region, due to unique hydrologyand water resources characteristics, it has become one of the most concerned regionsin global change research. In the current surface runoff research models, SCS-CNmodel is one of the widely applied models. As an important parameter in the SCS-CN, runoff curve number (CN) reflects the comprehensive features of fore-rainfall inthe model. The integration research of land use change and SCS-CN model standsfor the trend of agricultural non-point source pollution research. But the relative studyof karst surface, especially in the central region, is rarely found. With the increasingdevelopment of remote sensing technology, the use of remote sensing and GIStechnology to classified karst land use, and finally calculate the value of the karstsurface CN through field monitoring data, has great significance for the study ofnon-point source pollution in karsts.In this study, Chang River basin of Ruichang County in jiangxi province, whichis one sub-basin of Yangtze River, was regarded as study region.The multispectralimages from Landsat8coupled with field actual survey, were served as remotesensing data.After a series of process and analysis by using remote sensing image processingsoftware, include the preprocessing,NDVI calculation,temperature inversion,Principal component analysis, and Supervision classification processing, karst surfacedistribution diagram of different cover types in Chang River basin was obtained.In the meantime, the Karst surface runoff monitoring tests was conducted in thekarst surface runoff monitoring sites to calculate the CN value of different monitoringpoints, and finally the CN value distribution diagram in karst surface of differentcover types in overall Chang River basin was deduced by ArcGis software. The mainconclusions of this research are as follows:（1）Through field investigation and supervised classification, the most parts ofChangjiang river basin are karst surface being covered by vegetation, karst distributes widely, and the region is a typical karst distribution area with temperate continentalmonsoon climate（2）Land use/cover types of surface karst river basin can be divided into fourtypes: completely bared karst surface, more exposed karst surface, less exposedsurface karst, completely covered with vegetation karst surface.（3） Through CN value gain of karst surface, compared with normalgeomorphology, it can be concluded, karst land cover types have some influence onthe CN value, the higher the degree of exposed bared karst is, accordingly the greaterCN value is. The rank of CN values of different cover types karst surface in fourresearch areas are as follows: completely bared karst surface> more bared surfacekarst> less exposed surface karst> completely covered with vegetation karst surface.（4）Therefore, methodologically, the utilization of normalized differencevegetation index (NDVI) and temperature inversion data along with field trips toextract karst surface features information is feasible, and the conclusion is basicallycoincide with fieldwork situation. This may provides a good reference for karstconstitution analysis research on the method.