青藏高原东南部径流特征的空间规律及控制因子研究

采用青藏高原东南部的水文气象资料,对比分析了该地区23个(区间)流域的年径流深、集中度与集中期、基流系数、退水系数等径流特征及其空间分布规律,并进一步研究了这些径流特征的控制因子。结果表明:该地区径流特征的空间分布规律为年径流深从东南(700~1 300 mm)向西北(<400 mm)递减,而集中度则呈相反的空间格局(从<0.44增加到>0.59);退水系数及基流系数,在低海拔地区随高程增大而增大(分别为0.55~0.69、0.51~0.73),但在高海拔地区则随高程增大而减小(0.74~0.42、0.79~0.63)。本研究发现,青藏东南径流特征空间规律的控制因子,具有显著的区域分异:在低海拔流域(平均高程<3 000 m),降水是径流特征的主要影响因子;而在高海拔流域(平均高程>3 000 m),仅径流深和集中度受降水控制,其他特征则主要受温度、冻土、地形等条件的共同影响。可见,由于青藏高原东南部降水和冻土对气候变化敏感,该地区水资源时空分布格局将面临很大的不确定性,对此应予以充分重视。

Streamflow Characteristics in the Southeast Tibetan Plateau:Spatial Pattern and Control Factors

Hydrologic process on the southeast Tibetan Plateau(TP) under climate change is confronted with more uncertainty.A better understanding of streamflow characteristics as well as their spatial distribution and impact factors on the southeast TP will be critical to dealing with the influence exerted by climate change.In this study, we used the runoff and precipitation data to analyze streamflow characteristics and their spatial distribution via five hydrological signals i.e. averaged annual runoff depth, concentration degree, concentration time, baseflow index, and recession coefficient, and then investigated the related impact factors. Our results showed that in the southeast TP, annual runoff depth decreased from southeast (700-1 300 mm) to northwest (less than 400 mm), but concentration degree showed an opposite spatial distribution increasing from lower than 0.44 in southeast to above 0.59 in northwest. Both recession coefficient and baseflow index increased with elevation in lower altitude basins, ranging from 0.55 to 0.69 and from 0.51 to 0.73, respectively, while decreased in higher altitude basins, ranging from 0.74 to 0.72, and from 0.79 to 0.63, respectively. Impact factors showed noteworthy spatial difference in southeast TP basins. In lower altitude basins (average elevation approximately <3 000 m), precipitation was the main factor, whereas in higher altitude basins (average elevation approximately >3 000 m), only annual runoff depth and concentration degree were controlled by precipitation, while temperature and the underlying surface condition such as terrain and permafrost became the main factors of other characteristics. Since precipitation and permafrost conditions are susceptible to climate change, the time-spatial distribution of water resource in the southeast TP is prone to change, which needs sufficient attention.