Multiphase water transformation has great effects on alpine hydrology, but these effects remain unclear in the third pole region. Taking the Qilian Mountains as an example, the climate background and relative rates of multiphase water transformation were analyzed, and the runoff effect was evaluated based on long-term field observations. There are three climatic aspects driving multiphase water transformation, including lengthening ablation period, accelerative warming after 1990, and larger warming in the cryosphere belt than in the vegetation belt. The accelerative multiphase water transformation was quantified by three facts: the glacier area retreat rate accelerated by 50% after 1990, the percentage of snowfall in precipitation decreased by 7% after 1990, and the contribution from recycling moisture to precipitation increased by 60% from 1961-1990 to 1991-2016. Under the multiphase water transformation, the outlet runoff for three inland rivers increased by 5 × 108 m3/10 a after 1990. This runoff increase was concentrated mainly in the ablation period. For the seasonal runoff pattern, maximum runoff lagged maximum precipitation by one month under increasing glacier snow meltwater and thickening permafrost active layer. Meltwater from the cryosphere is a crucial runoff component in the Qilian Mountains. At present, these multiphase water transformations are accelerating, along with the yearly runoff increase, which will obviously have a profound impact on water resources management and flood control in the third pole region.
Keywords: Climate warming; Cryosphere; Multiphase water transformation; Qilian Mountains; Runoff effect.
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