Hydrological Response of Lhasa River to Climate Change and Permafrost Degradation in Xizang
拉萨河冬季径流对气候变暖和冻土退化的响应

Air temperature in the Lhasa River basin has increased by 0.54oC since 1990, particularly in winter and autumn, while precipitation did not increase in the same period. Based on climatological data of (1963-2003) and monthly runoff data of 28 years (1976-2004), the hydrological and geocryological response to the climate change was studied. The significant response to the temperature rising from the winter streamflow during November to February was detected, winter streamflow during December to February increased by 16% and in February by 22%. Correlation analysis between water flow and temperature indicated that the rise in temperature in October and November by 0.8-0.9oC resulted in the increase in winter streamflow, the seasonal frost at depth of 0.9-1.5 m became thinner comparing with that before the 1990s, the thickness decreased by about 14 cm. The hydrological response from winter flow in a permafrost basin is more sensitive and quicker than that of air temperature. There are un-certainties due to the lack of both soil frost and snowfall survey on the Tibetan Plateau.