Li Nianjie
About 70% of the discharge at the hydrological station in front of the Glacier No. 1, Tianshan is fed by ice-snow melt water, of which the annual distribution mainly depends on temperature fluctuation. There is no discharge during October to April, because of the subzero temperature, while the discharge during the period from June to August with a positive temperature is about 94% of the total amount.The discharge characteristics above the "critical line for discharge occurrence" is rather simple: part of the solid precipitation expenses through evaporation, other are transmitted to the "discharge occurrence area" through snow drift, avalanche, and glacial ice motion, in which only the amount of ice motion can be as many as 300,000m3/year.The magnitude of discharge is closely related to precipitation at the beginning of ablation period, during the stage of strong ablation, it is dependent on both air temperature and liquid precipitation; and at the end of ablation period, it depends mainly on the magnitude of positive temperature. Therefore, factors for regression analysis should be selected, based on their effects on the runoff in different stage, in order to do a reasonable extrapolation.Table 2 in the text shows that the results of "comparative observation with deduction convincing."Besides, the "extrapolation from relation curve" method is available because of its accuracy, although it is rough and simple and extrapolation part can be as large as 40%. Especially, during the glacial investigation when it is impossible to carry out a detailed glacial-hydrological observation, this method could be used and the hydrological data of the same river could be used to estimate the characteristic value of runoff in the glacial area. It might be a simple and practical method.
