| Under the present situation of the water and soil erosion problems, the research of the change rule from watershed hydrological processes helps to use and manage the water resources reasonably. It also can prevent the soil erosion. Nanting River is an important international river in China. It directly restricts the social and economic development in Lincang city, Yunnan province. In recent years, frequent flooding and soil erosion have become more and more serious. Scientific analysis of spatial-temporal feature of runoff and sediment, the discrimination of the key area soil erosion, and analysis of influencing factors of soil erosion can utilize the water resources more reasonable and promote the regional economic development and even improve the local residents’life.The research object of this research is Nanting River. The paper built the runoff and soil erosion model of Nanting River. And it is based on the DEM (digital elevation model), using the model of SWAT through GIS (Geographic Information System).This paper uses the measured data of the two hydrologic stations. The parameter sensitivity analysis is carried out, calibrated and validated on the model, so a complete model was built. Then it analyzes the reasons of water and soil erosion through the outputs of flow and sediment model and the spatial-temporal distribution characteristics of the runoff and sediment, combining with the measured hydrological and meteorological data. It identified the region of serious soil erosion. The optimum scheme of Subdivision of watershed was studied, and the hydrological response of different watershed division was analyzed. Established the different climate change scenarios of the next 50 years, and analyze the hydrological response of climate change. The results can provide scientific basis for the water resources planning, management, flooding control, and the prevention and control of soil and water loss in Nanting River.The main achievements of this research as follow:(1)The SWAT model has good applicability in Nanting River, especially the runoff model. We found that the monthly runoff simulation precision is the highest,R2 and ENS are both over 0.88.The simulation precision of soil erosion is slightly lower than the runoff, but it also achieved good effect, R2 and Ens are over 0.71. (2) The precipitation, evaporation and flow are all in decreasing trend from 1993 to 2012. Only the quantity of sediment levels off, the amount of evaporation reduced only 0.3% and the runoff decreased by 11.6%.Spatial distribution regularity of runoff and rainfall is highly consistent, the middle and upper reaches of it is less than the downstream area, and the maximum region is the downstream near the main channel, severe soil erosion areas are mainly distributed in the steep slope and the cultivated land of red soil area.(3) The basin has the tendency of precipitation increase and temperature increase within the next 50 years (2006-2055). Under the scenarios of RCP4.5, it’s not significant effect on runoff and sediment yield, especially the influence on sediment yield is very weak. It means that the runoff yield increased by 2.59%, the sediment yield only reduced by 0.33%. Under the condition of invariable precipitation, only the evaporation can significantly increase temperature, the runoff and sediment yield will be obviously reduced. Under the condition of constant temperature, the increase of precipitation can cause the increase of evaporation, runoff and sediment yield. And only the evaporation increased modestly. (4) The amount of the subdivision of watershed through the SWAT model should be more than 50 so that it could achieve a good simulation effect. Different schemes of the subdivision of watershed can cause significant effect for sediment, the maximum and the minimum range at 40.1%, but the influence on runoff simulation is slight, the range is within 6.3%. |
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