Analysis Of The Impact Of Precipitation And Land Use Changes On Runoff In Zhuanglang River Basin Based On SWAT Model

This paper takes the Zhuanglang River basin as the research object,and integrates linear trend regression,cumulative anomaly method and Mann-Kendall test method to analyze the meteorological and hydrological change trends and characteristics in the basin.At the same time,it analyzes and calculates based on the real data of land use in the basin.Obtain the land use change trend.The basin hydrological model is constructed based on the Arc SWAT module in Arc GIS.After SWAT-CUP calibration and verification,a hydrological model suitable for the Zhuanglang River basin is obtained.Combining the analysis of the change trend of meteorology and land use,set up a total of 20 different scenarios including three meteorological conditions of 5%,10%,and 15%increase in precipitation and four extreme land use conditions to study the runoff response law of the Zhuanglang River basin under changes in precipitation and land use.In terms of research on the trend of changes in meteorology,the real meteorological data used to study trend changes and construct the model comes from the daily-scale meteorological data from 1988 to 2017 at the two meteorological stations(Gaolan and Wushaoling)around the Zhuanglang River Basin and its surroundings.The missing meteorological data such as solar radiation is calculated based on existing monitoring data.According to calculations,annual maximum precipitation at the two meteorological sites occurs from June to September,and the total precipitation accounts for more than 70%of the annual precipitation.The distribution of temperature and solar radiation during the year also has obvious seasonal distribution characteristics.The summer temperature and solar radiation are higher than other months.Linear regression,cumulative anomaly and Mann Kendall test were used to analyze the interannual variation trend of meteorology which shows that the precipitation,temperature,and solar radiation at the two stations are all on the rise,and are accompanied by different sudden changes.The hydrological data comes from the daily runoff data of two hydrological stations(Tianzhu,Hongyazi)in the Zhuanglang River basin in the 2007-2016 National Hydrological Yearbook.After calculation and analysis,it is obtained that the annual runoffs of the two hydrological stations shows an opposite trend,that is,the annual runoff of Tianzhu station increases first and then decrease,while the annual runoff of Hongyazi station decrease first and then increase.Among them,the abrupt year of the annual runoff at Tianzhu station is 2013,and the abrupt year of the annual runoff at Hongyazi station is 2011 and 2014.In terms of land use change,according to the Zhuanglang River land use raster data in 2010 and 2015,the law of land use change is obtained through the calculation of the transfer matrix,that is,the maximum conversion area of each type of land is converted to cultivated land and grassland.In terms of watershed runoff response analysis,SWAT-CUP software uses the built-in SUFI-2 algorithm for parameter selection and validation.Based on the existing measured hydrological data,runoff data from 2006 to 2007 was set as the warm-up period,runoff data from 2007 to 2012 was the regular model rate,and runoff data from2015 to 2016 was the model verification period.After iterative calculation,the applicability evaluation results of the model are as follows,the calibration period was:the Wushengyi hydrological station R²=0.73,=0.59,the Hongyazi hydrological station R²=0.69,=0.65;the verification period was:the Tianzhu hydrology station R²=0.91,=0.85;the Hongyazi hydrological station R²=0.86,=0.57.The values of the above two parameters are in accordance with the accuracy standard,which proves that the Zhuanglang River Basin can be simulated using the SWAT model.The calibrated SWAT model is used to simulate monthly runoff for 20 change scenarios that are a combination of increased precipitation and extreme land use changes,and analyze the response of watershed runoff to changes in precipitation and land use.The results show that under the same land use conditions,the daily average runoff and annual runoff of the two stations increase with the increase of precipitation,and the change range of Tianzhu station is larger than that of Hongyazi station.Under the same precipitation conditions,the two stations have the largest increase in annual runoff when the grassland is transformed into cultivated land,and the smallest increase when the cultivated land is transformed into grassland When precipitation increases,different land use changes have different effects on the annual runoff of the two stations.Finally,Arc GIS software is used to analyze and calculate the HRU file in the model output file to explore the impact of the increase in precipitation during the flood season on the surface runoff per unit time in different regions of the basin.