Impacts Of Climate And Land Use Change On Surface Runoff

Affected by climatic factors and human activities,water shortages have occurred in the Heihe River Basin,and the ecological environment has been seriously damaged.The contradiction between water demand in the middle and lower reaches is difficult to alleviate,thus limiting the socio-economic development of the basin.The upstream of the Heihe River is the main runoff area of the Basin.Therefore,in the context of global change,it is necessary to analyze the impact of climate and land use change on surface runoff.According to the climate and land use change scenarios,the future runoff trends will be simulated to provide a reference for water resources planning in the basin.Based on the analysis of the characteristics and trends of the main hydro-meteorological factors in the upper reaches of the Heihe River from 1957 to 2017,the SWAT model was used to simulate the runoff changes in the upper reaches of the Heihe River from 1980 to 2008.Through scenario simulation,quantitative analysis of the contribution rate of climate and land use to runoff impact,and through the setting of future climate and land use scenarios,to explore the response of runoff changes under climate and land use change.The main findings are as follows:(1)During the period from 1957 to 2017,the temperature and precipitation of the main meteorological stations,Zhangye,Qilian,Yeniugou,and Tuole,in the upper reaches of the Heihe River showed an upward trend,and the climate showed a trend of warming and humidification.Based on the M-K test,the temperature change period was detected in the 1990 s,and the precipitation abrupt period was around the 1980 s.The runoff of the Yingluoxia station in the upper reaches of the Heihe River has shown an upward trend,and the detection mutation occurred in 2004.(2)The SWAT model of the upstream Heihe River was calibrated and verified.The results show that the determination coefficients of the calibration period and the verification period are 0.75 and 0.65,respectively,and the model efficiency coefficients are 0.71 and 0.63,indicating that the SWAT model has good applicability in the upper reaches of the Heihe River.(3)Determine the reference period and the interference period by analyzing the runoff mutation,combine the meteorological data and land use data in different periods,and calculate the runoff contribution rate of land use and climate change in the Heihe River Basin according to different scenarios.The results show that in the change of runoff,the contribution rate of climate change is much greater than land use change,which are 87.15% and 12.85% respectively.(4)The runoff of the upper reaches of the Heihe River is simulated by setting different climate change scenarios.The research shows that when the temperature decreases,the surface runoff increases.When the temperature rises,the change of surface runoff presents uncertainty due to the conflict effect caused by evaporation and snowmelt runoff.Runoff increases most when precipitation increases and temperature decreases.When the temperature rises and the precipitation decreases,the runoff reduction is most pronounced.(5)Simulating the runoff of the upper reaches of the Heihe River by setting different land use change scenarios,the research shows that natural trends and ecological protection trends lead to increased runoff,but in the ecological protection scenario,runoff increases more,while in economic development,runoff It is on a downward trend.Among them,the increase in forest land and grassland area has led to an increase in surface runoff.It can improve the regional climate to a certain extent and have a positive impact on surface runoff.Grassland grown under natural conditions is sparse,lacking interception of surface runoff and will increase surface runoff.The topography of cultivated land is relatively flat,and it is also prone to infiltration of precipitation,which will reduce surface runoff.