The Field of Equilibrium Line Altitude in the Ganga-Yarlung Zangbo Rivers System: Establishment and Its Environmental Significance

On the basis of the glacier inventory of China,the calculated snow line(ELA_hc) can be obtained,based on the linear relationship between ELA_h and H_me.It is revealed that the more number of the data of ELA_h,the more sound linear relationship between ELA_h and H_me in a glacier system is.In order to minimize the influence of topographical snow-line and other uncertain error,a method is adopted that to overlay the data points with a graticule mesh of 10′×10′,and then to calculate arithmetic average values of all the data points' longitude,latitude and ELA_hc in every square,utilizing such software as ArcGIS 9,etc.Then an ELA_hc distribution map,namely,the field of equilibrium line attitude,with an interval of 100 m,is produced by ordinary Kriging interpolation.In this paper it is found that: 1) The result in the recent equilibrium line attitude field is different from the previous ones from others,and shows more detail of glacier distribution in the southern Tibet glacier system,besides some common understanding;2) The field gradient of ELA_hc is greater in the south than in the north of the Ganga-Yarlung Zangbo Rivers system,with 5 m·km~-1 in the south and 0.5 m·km~-1 in the north.Furthermore,the distribution of ELA_hc is more complicated and the high ELA_hc values and low ELA_hc values appear alternative; 3) In this region the influence of precipitation on the distribution of ELA_hc is more evident than the influence of temperature,because precipitation decreases westwards,and the ELA_hc increases westwards,with a gradient of ELA_hc varying from 2.5 m·km~-1 to 4~6 m·km~-1 from east to west.