Application Of SWAT Model In The Upper Reaches Of Qingjiang River

Climate change and land use change are the main driving factors affecting hydrological water resources in a changing environment,and as the evolution of these two factors has a deepening impact on hydrological water resources,the study of hydrological water resources response changes in a changing environment has become one of the hot directions of hydrological water resources research.The headwaters of the Qingjiang River basin are an important biodiversity and soil conservation area,and the changes in hydrological and water resource response under the changing environment need to be clarified.In this paper,we collected the data required to construct the SWAT model and applied the SWAT model after parameter calibration and validation to land use change and climate change scenarios to analyze the hydrological response under different land use change and climate change scenarios.The main conclusions are as follows:1.SWAT model construction,rate calibration,and validationThe SWAT model was constructed by combining the elevation data,land type data,soil data and hydrometeorological data of the upper Qingjiang River basin,and the model was used to classify the upper Qingjiang River basin into 21 sub-basins and168 hydrological response units.The NSE and R~2of the SWAT model were 0.94 and above for monthly runoff simulation,0.75 and above for daily runoff simulation,and the PBIAS of both monthly and daily runoff simulation were within 10%,meeting the requirements of the model application.2.Hydrological response under land use change scenariosThree periods of land use data and extreme land use scenarios were selected from the upper Qingjiang River basin in 1985,1995 and 2012 to analyze the hydrological response status under different land use change scenarios.The results show that the area of forest land,construction land and water bodies increased and the area of cultivated land and grassland decreased in the upper Qingjiang River basin during1985-2012.The land conversion process mainly occurred among cropland,forest land and grassland and the integrated land dynamic attitude kept increasing.The conversion of forest and grassland to cropland leads to an increase in surface runoff and a decrease in subsurface runoff and soil infiltration in the watershed;the conversion of cropland and grassland to forest leads to the opposite hydrological response.The analysis of extreme land scenarios showed that cropland had a significant incremental effect on surface runoff and a significant intercepting effect on subsurface runoff and soil infiltration;the hydrological response of woodland was the opposite of that of cropland.3.Hydrological response under climate change scenariosThe incremental scenario method was used to set 49 future climate change scenarios in the upper reaches of the Qingjiang River basin,and the hydrological response under different climate change scenarios was analyzed.The results show that:(1).Runoff,surface runoff,and subsurface runoff are more sensitive to changes in precipitation than changes in temperature,and evapotranspiration is more sensitive to changes in temperature than changes in precipitation.(2).Runoff,surface runoff,and subsurface runoff showed a negative correlation with air temperature,and evapotranspiration showed a positive correlation with air temperature.The rate of change of runoff,surface runoff,and subsurface runoff is affected by the increase in temperature,and the rate of change of evapotranspiration is affected by the decrease in temperature.(3).Runoff,surface runoff,subsurface runoff,and evapotranspiration all showed positive correlations with precipitation.Among them,the increase in precipitation has a strong influence on the rate of change of runoff and surface runoff,and the decrease in precipitation has a strong influence on the rate of change of evapotranspiration.(4).The A1 scenario(T+2,P(1-20%))produced the greatest decrease in annual average runoff,surface runoff,and subsurface runoff in the study area,while the A49 scenario(T-2,P(1+20%)produced the greatest increase in annual average runoff,surface runoff,and subsurface runoff.The A43 scenario(T-2,P(1-20%))resulted in the greatest decrease in mean annual evapotranspiration in the study area,while the A7 scenario(T+2,P(1+20%)resulted in the greatest increase.