Simulation Analysis Of Runoff Change In Heihe Oasis Area Based On SWAT Model

Under the background of global change,quantitative analysis of the characteristics of climate and land use changes and runoff changes can provide a basis for decision-making for the rational allocation of water resources in the basin.This paper selects the Heihe oasis area as the study area,uses meteorological,land use and measured runoff data to analyze the characteristics of climate,runoff and land use change in the study area,and sets different climate and land use change scenarios to simulate the runoff in the study area based on the S WAT model.Analyzing the characteristics of runoff change,the main research conclusions are as follows:(1)The climate in the study area generally changes in the direction of warm and wet,and the temperature,precipitation and runoff all show a significant upward trend,and there are differences in the sudden change period.The period of sudden change in temperature mainly occurred from 1994 to 1996,the period of sudden change in precipitation occurred from 1970 to 1990,and the sudden change of annual runoff occurred in 2004.From 2000 to 2018,the land use structure remained stable,with the proportion of bare land,grassland and forest land.The characteristics of land use type transfer are that all other land use types are transferred to cultivated land,grassland and bare land.(2)Construct the SWAT model in the Heihe oasis area,and determine the relevant parameters according to the experimental results,combined with the existing relevant research,and complete the model calibration and verification.The Ens values of the regular and validation models are 0.51 and 0.61,respectively,and the R2 is 0.71 and 0.72,respectively.The accuracy is up to the standard,and the simulation results are basically credible.According to the contribution of climate and land use to runoff,it can be seen that the contribution level of climate change to runoff Slightly higher than land use,accounting for 59.93%and 40.07%respectively.(3)Under different climate change scenarios,the runoff change rate generally increases with the increase of precipitation and decreases with the increase of temperature.Specifically,when the temperature is constant,the runoff change rate increases with the increase of precipitation,and when the precipitation remains constant,the runoff change rate decreases with the increase of temperature;when the temperature and precipitation decrease,the runoff change rate shows a downward trend;When the temperature decreased and the precipitation increased,the runoff change rate showed an upward trend.When the temperature dropped by 2℃ and the precipitation increased by 20%,the runoff increased rapidly,which was 39.11%;When the temperature increased and the precipitation decreased,the runoff change rate showed a rapid increase of 39.11%,a downward trend;when the temperature and precipitation increase,the runoff change rate shows an upward trend,but the rising speed is not obvious.It can be considered that precipitation has a positive effect on runoff change,and temperature has a negative effect on runoff change.(4)Under the extreme land use and future land use scenarios,the runoff shows fluctuating changes,and there are slight differences in the magnitude of runoff changes.Under the extreme land use scenario,in 2018,the simulation results of monthly average runoff under the initial land use,all-arable land and all-grassland scenarios are:20.42 m3/s,12.58 m3/s,and 20.82 m3/s,respectively.Compared with the initial land use,the runoff of the whole farmland scenario decreased by 38.36%,and the whole grassland scenario increased by 65.41%.In 2030,the runoff change rate under the all-arable land scenario is-37.77%,and the runoff change rate for the whole grassland is 65.41%.It can be considered that the all-arable land scenario has a negative effect on the runoff change,and the whole-grassland scenario promotes the increase of runoff;the future land use scenario compared with 2020,the monthly average runoff under the natural growth and economic development scenarios in 2025 will decrease by 1.10%and 1.09%,respectively,and the runoff under the ecological protection scenario will increase by 4.53%.In 2030,natural growth,economic development,ecological compared with 2020,the monthly average runoff under the protection scenario has a change rate of-1.40%,-1.38%and 9.90%,respectively.It can be considered that the natural growth and economic development scenarios have a negative impact on the runoff change,while the ecological protection scenario has a positive effect.