Application Of Distributed Hydrological Model SWAT To Runoff Simulation In Huotong River Basin

In recent years,research on process effects of hydrological processes in river basins based on land use change and climate change has become a hot topic.Hydrological model,as an effective method for the study of runoff change under human activities and climate change,was increasingly widely used.Hydrological models can be used to establish the response of hydrological elements such as rainfall,evapotranspiration,soil infiltration,and groundwater to runoff.Process to quantitatively reveal and evaluate basins runoff change mechanisms under the influence of land use/land cover and climate change.In this study,the Huotongxi basins was used as the research area.The Huotongxi basins was affected by the terrain.The meteorological elements of precipitation were significantly different in the region.It belongs to the mid-subtropical maritime monsoon climate.There were many water conservancy engineering facilities,so research on the effects of land use change and hydrological processes under climate change in Huotongxi basin had important theoretical significance and practical value for rational planning and allocation of water resources in the basin.Based on the SWAT model,this study used meteorological and hydrological data,combined with other auxiliary data such as DEM,soil attribute data,land use data,and soil type maps,to build a distributed hydrological model in Huotongxi basins.Based on this,the impact of land use change and climate change on runoff before and after the completion of the Huotongxi reservoir was quantitatively explored,and future land use and climate change scenarios were designed to drive SWAT models to simulate and analyze the trend of future runoff in the catchment.The main work and conclusions of this paper are as follows:(1)Based on SWAT distributed hydrological model,using DEM data,soil,land use data,and meteorological data,and calculate soil property data to construct soil property dataset in Huotongxi basins;The 2016 weather data builds a weather generator,and adds 9 rain stations from 2001 to 2016 to build a Huo Tongxi weather database.Using GIS and RS technologies to interpret land use data,digitize soil type maps,and process DEM data,construct a SWAT model-related spatial database in the Huotongxi basins.(2)On the basis of considering the impact of land use change on runoff and the characteristics of reservoir operation in the study area,this study adopts subsection calibration combined with the SUFI2 algorithm in SWAT?CUP program,which improves the simulation accuracy of the model and reduces the uncertainty of the model.In the daily scale runoff simulation of huotongxi basin from 2001 to 2016,the minimum efficiency coefficient of regular rate is more than 0.65,and the minimum determination coefficient is more than 0.66.The daily scale simulation determination coefficient of Hongkou reservoir downstream control basin can reach 0.85 by adding the reservoir outflow flow data,which shows that the water reservoir data has an important impact on the accuracy of model simulation.The average coefficient of runoff determination R~2 is 0.96 and the average coefficient of efficiency NSE is 0.94 at the monthly scale;in the annual scale,the average coefficient of efficiency of each station is 0.88 and 0.97 at the annual scale,the average coefficient of efficiency in the verification period is 0.87 and the average coefficient of determination is 1.The runoff simulation results at the daily,monthly and annual scales can meet the application accuracy requirements of SWAT model.(3)The reservoir has a significant impact on extreme floods and extreme dry water,and plays a role in eliminating peaks and supplementing dryness.In this study,taking the operating time of the reservoir as a node,through six different runoff simulation scenarios,the impact of climate change,land use change,and reservoir operation on Huotongxi runoff was quantitatively analyzed.It was found that climate change is the main contribution factor of runoff change in Huotongxi basins,with a contribution rate of 65.82%,followed by reservoir operation of 17.25%,and land use of 16.93%.The areas with high water production value are mainly concentrated on the dam area of Hongkou reservoir.The study found that the operation of the reservoir not only did not reduce the annual runoff depth,but increased it.Based on the monthly changes in the runoff of the Yangzhongban Hydrological Station in 2008-2016 whether the reservoir is operating in the basin,it was found that the reservoir passed during the flood season(4-10 Month)Intercept and store water during the high water season.During the non-flood season(November,December,January-March),open and release the water during the dry season to adjust the hydrological process of the river basin.Among them,the two months with the largest increase and change are February and March,and the increase of monthly average runoff depth can reach38.26%and 29.22%of that when the reservoir is not in operation.By simulating future extreme land use scenarios,under the same conditions,the water conservation capacity of forest land is greater than that of grassland,and the water conservation capacity of grassland is greater than that of arable land.(4)The trend analysis of temperature and precipitation over the past 50 years in Huotongxi basins was carried out by linear regression method and Mann Kendall nonparametric test analysis.In the past 50 years,the interannual precipitation of the basin has been on the rise,with a change rate of 29.81mm/10a,and there are abrupt precipitation points around 2013.The interannual temperature change in the basin has been on the rise,with a change rate of 0.289?/10A,and a temperature mutation point appeared in 1996.(5)Based on the change trend of temperature and precipitation in the past 50 years,eight climate changes in the next 10 years(2027)and 40 years(2047)were simulated.The results show that when the temperature is constant and the precipitation changes,the runoff depth increases by 18.83mm per 1%increase in precipitation When the precipitation remains unchanged and the temperature changes,the annual average runoff depth at the outlet of the basin decreases by 13.74mm with each 1? increase in the basin temperature.It can be seen that precipitation changes in the basin are more sensitive to changes in runoff than temperature changes.The analysis of 24 climate change scenarios in the next 40 years based on the fourth IPCC Assessment report shows that when the temperature remains unchanged,the precipitation will only increase by 10%,and the annual runoff depth of the basin will increase by 195.5mm;when the precipitation remains unchanged,the annual runoff depth of the basin will only increase by 5.13mm when the temperature decreases by1?.It will shows that compared with the 1%precipitation change and the 1? temperature change under the climate change scenario,the greater the increase in precipitation,the more significant the synergy effect on the river basin runoff.The higher the contribution,the more precipitation decreases,and the stronger the resistance to runoff,the more it decreases.When the temperature increases,the river basin runoff also decreases,but the amount of change decreases.When the temperature decreases,the runoff of the river basin will increase accordingly,and the increase will increase.At the same time,under climate change,precipitation changes in the Huotongxi basins dominate the runoff,and temperature changes take a secondary role compared to precipitation changes.