天山玛纳斯河冬季径流对暖冬和冻土退化的响应

天山高山地区大范围为冻土区,冻土的存在对水文过程有极大的影响.20世纪90年代以来,玛纳斯河流域气温10 a升高了0.54℃,以冬季升温为主,降水量没有增加趋势.应用1957—2004年近48 a的气候和水文月资料,研究了具有多年冻土的高海拔河流的冻土和水文响应.检测到12月至翌年2月气温升高0.8~0.9℃时冬季径流量响应显著,冬季径流在12至翌年2月份增加了14%~26%,其中1月份增加26%.遥相关分析表明,10~11月的水量增大也可导致冬季河流水量增多,1.5~3.0 m的活动层的深度和温度变化导致了这些响应.冻土区的冬季径流水文响应比气温更快、更显著.但冻土和积雪观测的不足使冬季水文变化具有不确定性.

Hydrological Response of Winter Streamflow to Climate Change and Permafrost Degradation in Manas Watershed, Tianshan Mountains

Watersheds in the permafrost regions have been under the influence of climate change for centuries,especially in the last two decades when permafrost degradation was accelerated and intensified.This degradation was designed to speed up water transfer,to increase soil erosion,to improve agricultural productivity and ecological environment.It is important to evaluate the effects of these impacts to hydrology in order to develop a sustainable water resources management in cold regions.This study evaluated the changes in both winter air temperature and stream-flow regime for a selected drainage basin in high altitude following a large scale of permafrost degradation in the Tianshan Mountains,China.The non-parametric Mann-Kendall tests were used to identify the trends in both winter air temperature and stream-flow under confident levels at 99% and 95%,respectively.The results showed a significant upward trend.Pettitt's test indicated that shift points of winter stream-flow and temperature occurred in 1985 and 1995,respectively.Comparison of winter flow duration for two 24-years periods starting and ending in 1980 showed significantly an upward trend in winter stream-flow.Increase in winter stream-flow varied from 14% to 26%,and in January it was 26%.It is found that there are reliable positive non-linear correlations in the increase of winter stream-flow between October and November.The increase of winter stream-flow in October and November resulted in the increase of winter stream-flow.Both rise of temperature and increase of discharge at the beginning of frost can greatly increase drainage of subsurface water in January,when the maximum variability occur The total increase in winter flow is increasing with time,with a significant change from the 1990s.However,there is an uncertainty about the winter stream-flow change due to short of observations of permafrost and snow cover in the Tianshan Mountains,China.