A Preliminary Study on the Drainage System in the Ablation Area of the Glacier No.1 at the Source of Urumqi River
Kang Ersi (Lanzhou Institute of Glaciology and Geocryology, Chinese Academy of Sciences)
The water channels are developed on the glacial surface and at the glacial sides, some meltwater runs into or under the glacier throuth the crevasses, the moulins and the glacial sides, through the englacial-subglacial water channels and finally out off the glacier, forming the glacial drainage system. The salt tracer experiment was conducted at the Glacier No.1, 7 injection points of which were distributed on the ablation area and the accumulation area immediatly above the equilibrum line, the one dimensional dispersion equation is employed to calculate the curves of the salt condensation versus time and the dispersion coefficient. The observation and calculation show that the confluence of meltwater is rather rapid in the ablation area. It only takes 1-2 hours for the meltwater to run to the glacial gauge station during the period of complete development of the glacial drainage system, but in the accumulation area, the retardation of the snow and firn layers to meltwater runoff should be considered. The storage function of the glacier to meltwater runoff is weak, it makes the meltwater runoff nearly all drained out off the glacier, after a short time stay in the drainage system. The anabranches, flow eddies and the retardation of sediments to runoff exist in the drainage system, it makes the observed curves of the salt condensation versus time lower and extending time longer than that of calculated curves, but the prolonged time is generally only in several to 15 minutes, even in the accumulation area hear the equilibrium line is only in about 60 minutes. The dispersion equation can basically be applied to simulate the curves of salt condensation versus time of the salt tracer experiment, this clarifies that the englacial-subglacial water channels are rather unitary, instead of complex divergence. The dispersion coefficient of the drainage system in the ablation area is calculated generally to be 0.5-1.5 m2 / s.