Tracing the major source area of the mountainous runoff generation of the Heihe River in northwest China using stable isotope technique

Based on the data of δ¹⁸O in precipitation during the period of April 2006 through May 2007 in the upper catchment of the main stream of the Heihe River in the Qilian Mountains, we found that there existed an evident altitude effect on δ¹⁸O in precipitation, and the δ¹⁸O-altitude gradient was −0.18%/100 m. When δ¹⁸O in river water at the outlet of the mountainous drainage area of the main stream of the Heihe River was combined with the δ¹⁸O-altitude relation, it was realized that the mountainous runoff was generated mostly at high altitudes. Using two component models, we revealed that 80.2% of the annual total mountainous runoff amount was generated at the alpine permafrost-snow-ice zone with an altitude of above 3600 m a.s.l. Supported by the International Partnership Project of Chinese Academy of Sciences (Grant No. CXTD-Z2005-2), National Natural Science Foundation of China (Grant No.4052501), National Basic Research Program of China (Grant No. 2005CB42 2003) and Innovation Research Project of Chinese Academy of Sciences (Grant No. kzcx2-yw-310)