祁连山区黑河上游多年冻土分布考察

高山多年冻土的分布及土壤季节冻融过程对地表水文过程、 生态系统、 碳循环及寒区工程建设等都有很大的影响. 黑河上游地处祁连山中东部, 属于高原亚寒带半干旱气候, 研究黑河流域多年冻土分布对于系统理解该区域的生态-水文过程、 气候与环境变化以及水资源评价、 工程建设等非常重要. 2011年6-8月对黑河干流源头西支开展了多年冻土调查, 沿二尕公路(S204)在热水大坂垭口至石棉矿岔口之间区域, 完成测温孔7眼, 并布设测温管进行地温监测. 根据勘察、 钻探及测温资料, 确定了黑河源头地区山地多年冻土下界为海拔3 650~3 700 m之间. 受高度地带性的控制, 随着海拔的降低, 活动层厚度由在海拔4 132 m时的1.6 m增加至在多年冻土下界处的约4.0 m, 多年冻土年平均地温也相应的由-1.7℃增加到0.0℃左右, 而多年冻土厚度由100 m以上减小到多年冻土下界处的0.0 m. 同时, 坡度和坡向、 岩性、 含水(冰)量、 地下水、 河水等局地因素对多年冻土温度和厚度也有重要的作用.

Investigation on Permafrost Distribution over the Upper Reaches of the Heihe River in the Qilian Mountains

Permafrost and seasonally frozen ground have a dramatic influence on surface hydrological processes, ecosystems, carbon cycle, and infrastructures in cold regions. The upper reaches of the Heihe River are located in the eastern part of the Qilian Mountains, where climate is cold and semi-arid. The study of permafrost distribution in Heihe River basin is of great importance for systematically understanding the regional eco-hydrological process, climate and environmental changes, water resources assessment and construction, etc. Field investigation on distribution of permafrost had been conducted over the upper reaches of the river during the summer of 2011. Seven boreholes ranging from 20 to 100 m in depths were drilled in early August, 2011. Based on borehole drilling information and temperature profiles measured at least two months after the drilling, it is found that the lower bound of permafrost is at between 3 650 m and 3 700 m a. s. l. Depending on altitude, the active layer depth varies from 1.6 m at 4 132 m a. s. l. to about 4.0 m near the lower bound of permafrost at a little above 3 650 m a. s. l. Mean annual ground temperatures at the depth of zero annual amplitude increases from -1.7℃ at 4 132 m a. s. l. to near 0.0℃ at the lower bound of permafrost. Permafrost depth decreases from more than 100 m at 4 132 m a. s. l. to 0.0 m as moving down to 3 650 m a. s. l. At the same time, the other local factors, such as slope, aspect, soil type, soil water(ice)content, vegetation and river channel, may also have significant effect on permafrost conditions.