Quantitative Research On The Influence Of Permafrost Degradation On Runoff In Upper Reaches Of Heihe Based On Budyko Model

The upper reaches of the Heihe lie in the alpine mountainous region of Qilian in the northeast of the Tibetan Plateau.It has much permafrost and seasonal frozen soil with high altitude,low temperature,cold and humid climate.In the past few decades,Permafrost in the upper reaches of the Heihe has significantly degraded due to climate warming,which changed the hydrological processes such as runoff and confluence in the basin.Therefore,it is necessary to study the permafrost degradation and its hydrological response in order to provide a certain theoretical basis for local water resources management.In this paper,the surface 0 cm temperature data of the 12 meteorological stations in the study area and surrounding areas are used.The modularization function of Arc GIS is used to simulate the distribution of permafrost in the upper reaches of Heihe.The law of spatio-temporal variation of the coverage of frozen soil over many years;using Stephen's formula to calculate the thickness of the active layer in the study area,the linear regression analysis of the precipitation,evaporation,drought index of Qilian,Yeniugou,and Qilian,Zamashke and Yingluoxia in the same period The interannual variation law of the regression index of hydrological stations;the improved Kalinin method was used to calculate the base flow of the watershed in the study area,and the cumulative anomalies,Mann-Kendall test and sliding T test were used to measure the runoff data of the three hydrological stations.Variability analysis to study its changing trend;because runoff in different watersheds responds differently to permafrost degradation,this article first does not assume that permafrost degradation increases or decreases runoff,but first quantifies runoff through the water-heat balance equation in the Budyko framework Response to climate change and watershed landscape changes,including precipitation,changes in potential evapotranspiration,and permafrost regression Impact.After deducing the contribution of permafrost degradation in the upper reaches of the Heihe to runoff changes,the flow response of permafrost degradation is further discussed in detail.The results show that from 1980 to 2016,the permafrost in the upper reaches of the Heihe deteriorated significantly.The average annual decline rate of the permafrost area is about 81km2/a,the average elevation rate of the lower boundary elevation is12m/a,and the active layer thickness rise rate is 0.61cm/a.Under this background,the annual average runoff of three representative hydrological stations in Qilian,Zamask and Yingluoxia all showed an increasing trend,with an average annual increase of 24.4m3/s,56.3m3/s and 132.6m3/s.After conducting mutation test,it was found that three hydrological stations had significant mutations in 1980,2007 and2007 respectively.In the Babao River Basin and Yeniugou River Basin,climate change contributed 84.96% and 34.73% to runoff changes,respectively,and the degradation of frozen soil was 20.73% and 28.67%.The correlation analysis of precipitation,negative accumulated temperature and runoff found that the summer and autumn rainfall in the upper reaches of the Heihe were the main sources of runoff during the same period.The degradation of frozen soil increased the discharge of groundwater to a certain extent,slowed down the winter backwater process,and caused runoff The distribution became more even during the year.