Hydrological Simulation And Parameter Uncertainty Analysis Of Guishui River Basin

Hydrological Modeling and Uncertainty Analysis of Parameters in the Guishui River BasinOn October 18,2019,the Intergovernmental Panel on climate change(IPCC)released the IPCC global warming 1.5 ? special report in Incheon,South Korea.The report points out that compared with limiting global warming to 2 ?,limiting to 1.5 ?has obvious benefits for human beings and natural ecosystems,while ensuring more sustainable and equitable society.It is intended to show that global warming is the general trend.At the same time,in our country,the idea that green water and green mountains are golden mountains and silver mountains is deeply rooted in people's hearts.In the Guishui River Basin,"returning farmland to forests and grass" is changing the land use and land cover situation in the basin.Therefore,under the condition of land cover and global warming,the original hydrological cycle of the basin will change profoundly.Scientific analysis of hydrological cycle process and change law under the condition of land use,temperature and rainfall changes is of great significance to the rational utilization of water resources and the sustainable development of economy and society in the future.Taking the Guishui River Basin in Yanqing District,Beijing,where the Winter Olympic Games are held,as an example,this paper selects SWAT hydrological model,based on Arc GIS 9.3 software,and uses swat-cup to complete the construction,calibration and verification of the distributed hydrological model.Using the historical inversion method and extreme land use method,the SWAT model based on the land use in 2000 and 2017 is established,and the SWAT Model under three extreme land use and cover conditions is established simultaneously by comparing the land use in two phases.The changes of surface runoff caused by three extreme land use / cover conditions are analyzed.Through the hypothetical climate scenario method,this study constructs the simulation scenarios under various climate change conditions.The temperature increases by 0.5 ?,1 ?,1.5 ? and 2 ? respectively.The rainfall decreased by 20%,10%,increased by 10%,20% respectively.Twenty five climate models were established by combining the above two scenarios.Then compared with the same rainfall variation range under normal temperature to determine the impact of temperature rise on surface runoff under different rainfall conditions.The main results of this study are as follows:(1)Collect and sort out the DEM map,soil,climate and other data of Guishui River Basin,and establish the attribute database such as meteorological database and soil database.SWAT hydrological model was established and successfully operated.(2)Using the Swat(soil and water assessment tool)model to carry out monthly scale hydrological simulation of Guishui River Basin,using the sufi-2(sequential uncertainty fitting)algorithm to analyze the sensitivity of parameters,and according to the automatic calibration of swat-cup,the uncertainty of the P-factor and R-factor analysis model is obtained.The calibration results show that the rate regular determination coefficient R ^ 2 is 0.65,and the efficiency coefficient NSE is 0.61;validation R ^ 2 is0.89,NSE is 0.88,P-factor is greater than 0.5,R-factor is less than 0.3.Through the above analysis,it can be concluded that the model has a good effect on the hydrological simulation of Guishui River Basin.(3)Using the historical inversion method and extreme land use method,the SWAT model based on the land use in 2000 and 2017 is established,and the SWAT Model under three extreme land use and cover conditions is established simultaneously by comparing the land use in two phases.The meteorological data of 2017 is input into the model and the output monthly runoff results are analyzed.The results show that:compared with the simulation results of the model using the land use data of 2000,the runoff of 2017 is less and the runoff hydrograph is more gentle.The results show that the increase of forest land area will reduce the surface runoff and make the runoff path more gentle,and the increase of cultivated land and grassland area will increase the surface runoff and the flood risk under the condition of continuous rainfall in Dalian.(4)Based on the hypothetical climate scenario method,25 climate change scenarios were constructed by using the underlying surface conditions of the basin in 2017 and changing the meteorological data in 2017.SWAT simulation results show that the runoff of Guishui River has a positive correlation with rainfall and a negative correlation with temperature.The runoff of Guishui River will be reduced by 4.43%,7.39%,10.17% and11.88% when the temperature increases by 0.5 ?,1 ?,1.5 ? and 2 ? respectively when the rainfall of the river basin remains unchanged;when the temperature of the river basin remains unchanged,the rainfall will be reduced by 10%,20%,the runoff of Guishui River will be reduced by 12.42%,25.44%,the precipitation will be increased by10%,20%,and the runoff of Guishui River will be increased by 23.95%,34.93%respectively.The runoff of Guishui River is affected by both temperature and precipitation.The biggest increase of runoff in Guishui River Basin is that the temperature in the basin remains unchanged,the precipitation increases by 20%,and the runoff increases by34.93%;the biggest decrease of runoff in Guishui River Basin is that the temperature increases by 2 ?,the precipitation decreases by 20%,and the runoff decreases by41.72%.In conclusion,this study provides a model for simulating the surface runoff of Guishui River Basin.Through the simulation and analysis of the surface runoff under different land use and meteorological change conditions,it provides help for the basin to cope with the adverse effects of global warming in the future and achieve sustainable development and rational allocation of water resources.