The Changes In Underlying Surface And Its Impact On The Runoff In The Source Areas Of The Yellow River And Golmud River

Under the background of global warming,the change of underlying surface in alpine regions and its influence on water resources is a hot topic in ecological hydrology.As the "water tower of Asia",the Qinghai-Tibet Plateau is the source region of many important rivers.It is of great significance for water resources management to study the influence of changes in vegetation,permafrost and other underlying surface factors on hydrological processes in the alpine mountains of the Qinghai-Tibet Plateau under the influence of climate change.Taking the source region of the Yellow River and the source region of the Golmud River as typical basins,this paper studied the influence of underlying surface changes on runoff,and quantitatively distinguished the influence of climate,vegetation,frozen soil and other factors on runoff changes.This paper collected Terra and Aqua/MODIS LAI data and meteorological data of the same period from 2003 to 2015 in the study area,discussed the spatial pattern of vegetation phenological change in the source region of the Yellow River,and analyzed the correlation between climate factors and vegetation phenological characteristics.The annual runoff of the source of the Yellow River and the source of the Golmud River was analyzed by using the Mann-Kendall trend test and the sliding T test.Based on the variation characteristics of underlying surface,the semi-empirical fitting formula of Budyko model parameters was established.On this basis,the influence of climatic and non-climatic factors(vegetation,frozen soil,etc.)on runoff was quantitatively distinguished by Budyko model and modified double mass curve method(MDMC).The results showed that the vegetation cover in the source region of the Yellow River and the source region of the Golmud River showed an overall trend of improvement,while the frozen soil showed a trend of degradation.The vegetation growth season in the source region of the Yellow River is from early may to early October.The precipitation plays an important role in the spatial pattern of the start and end dates of the growing season,while the temperature mainly affects the variation trend of the start date of the growing season.From 1965 to 2015,runoff in the source region of the Yellow River first decreased and then increased on the whole,while runoff in the source region of the Golmud River increased on the whole during the same period.The quantitative analysis shows that the variation of runoff caused by climatic factors in the source region of the Yellow River and the source region of Golmud is much larger than that caused by the variation of underlying surface,and the increase of precipitation is the main reason for the increase of runoff.The degradation of permafrost in the source region of the Yellow River reduces runoff,and the contribution of vegetation and other factors to runoff is minimal.The degradation of permafrost reduces runoff and the increase of vegetation in the source region of Golmud River.The research results provide valuable reference for water resources management in the source region of the Yellow River and the source region of the Golmud River.