冻土冻融对地下水的影响:以祁连山多年冻土区大通河谷融区为例

Impact of Freezing-Thawing Process of Frozen Soil on Groundwater:A Case Study in the Datong River Valley Area of the Qilian Permafrost Region

冻土区地下水的形成、补给、径流、排泄方式以及地球化学特征受到冻土分布及其季节性冻融过程的强烈影响。以地处祁连山多年冻土区的大通河谷融区为典型研究区,基于钻探、坑探和地球物理工作查明了区内冻土特征和分布情况;结合水文地质观测及抽水试验,分析了研究区河流融区内地下水的赋存条件,深入研究了区内冻土冻融过程影响下地下水的水文地质和水化学特征,认为冻土冻融过程决定了研究区的地质和水文地质条件,控制着地下水的补给、径流、排泄方式,特别是对地下水质有优化作用——冻土区地下水质明显优于非冻土区。冻土区地下水成因和赋存条件研究对于其开发利用有重要意义。

The formation, recharge-flow-discharge patterns, and geochemical characteristics of groundwa- ter in permafrost or seasonal frozen soil areas are strongly affected by their distribution and freezing-tha- wing process. Taking Datong River valley area of the Qilian permafrost region as a typical study area, this paper investigated the locations and the characteristics of permafrost and seasonal frozen soil based on drill- ing, pit tests and geophysical surveys. The geological conditions for the occurrence of groundwater in the study area were also evaluated via hydrogeological observations and pumping tests. The hydrogeological and geochemical features of the groundwater under the effects of freezing-thawing process of frozen soils were further studied. The results indicate that the freezing-thawing process of frozen soils has a significant impact on the basic geological and hydrogeological conditions of the study area, and therefore controls the recharge-flow-discharge patterns of the groundwater. More importantly, this process helps improve the groundwater quality in the frozen soil areas. The research on the geological geneses and conditions for groundwater in permafrost or frozen soil areas benefits the exploitation and utilization of groundwater in such areas.