THE RESPONSE OF RIVER DISCHARGE TO CLIMATE WARMING IN COLD REGION OVER CHINA
This paper summarized some results of responses of river discharge to climate warming in cold region over China. The climate warming has strongly affected on discharge in cold region rivers in recent decades. The glacier, snow and permafrost are sensitive to climate change and related to river discharge. The measured glacier runoff has significantly increased by more than 37% during 1980 ~2006 due to climate wanning in the basin of Glacier No. 1 in ürümqi River source (43°05'N,86°49'E) and 25% runoff increase is contributed from glacier mass loss. The simulated glacier runoff from degree-day model also shows strongly increase in Tarim Basin during 1960 ～2006. The glacier runoff would increase in earlier period of climate warming and then would decrease. The glacier runoff results from glacier flow model shows that the time and volume of the glacier runoff peak induced by climate warming in future depended on the glacier size and temperature increase rate. The enhanced glacier ablation also has lead to the extension of lake supplied by glacier, increase of glacier lake flood frequency. The climate warming also leaded to the early snow melting, consequently discharge increase in spring and shifted the hydrological regime in some rivers in the West China. The maximum monthly discharge has shifted from June to May at Altay Hydrological Station of Kelan River Basin in the Irtysh River of Altai Mountains during 1960 ~ 2005. There is significant relationship between the permafrost coverage and the ratio of monthly maximum and minimum discharge in Lena River in Siberia and some additional data from some rivers in the West China and Arctic region further identified the relationship. This relationship indicates that the permafrost coverage of river basin controlled the hydrological regime in the basin with more than 60% of permafrost coverage and has no much effect on hydrological regime in the basin with less 40% of permafrost coverage. The relationship implies that the permafrost degradation will lead to flat hydrological regime in cold region with permafrost. The hydrological region in cold region rivers has been flat during last 50a due to permafrost degradation.
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