摘要
为从整体上认识多年冻土活动层土壤水文过程季节变异特性,以黄河源区巴颜喀拉山北坡冻土剖面为例,结合大气降水、冻土土壤水分、冻土层上水的野外观测,采用HYDRUS-1D软件冻融模块进行模拟分析,分析冻融作用对活动层土壤水文过程的影响,研究结果表明:(1)冻土层上水位与土壤水热之间存在着相互影响、相互作用的关系,依据活动层土壤温度变化,基于冻融过程,多年冻土活动层土壤水分与冻土层上水位可划分为冻结稳定、快速融化、融化稳定和快速冻结4个阶段。(2)降雨入渗是坡面尺度下活动层土壤水文过程的主要驱动力,活动层冻融锋面是主要限制性因素,受冻融过程影响,冻结期降雨减少,土壤冻结,土壤储水能力下降,土壤水分下渗停止,坡面侧向流动减弱,土壤水分和冻土层上水位处于下降趋势;融化期降雨增多,土壤融化,土壤储水能力上升,土壤水分下渗强烈,坡面侧向流动增强,土壤水分和冻土层上水位处于上升趋势。(3)受坡面地形影响,上坡活动层厚度大于下坡,上坡冻融锋面变化较下坡平缓,上坡土壤水分和冻土层上水位的变化幅度相对下坡较为平缓,而上坡土壤水分相对下坡含量较低,下坡冻土层上水位相对稳定。
In this paper,a permafrost cross-section at the northern slope of the Bayan Har Mountains in the source region of the Yellow River is studied. Based on the field observations,herein,the data has been collected from various sources including atmospheric precipitation,soil moisture,and supra-permafrost waterflow. According to the variations of the gathered data,the seasonal variability of soil hydrological processes in active layers is statistically investigated.In addition,the influence of freeze-thaw action on the hydrological process in an activity layer is numerically simulated by HYDRUS-1 D software package. The obtained results are summarized in the following:(1) There is a close relationship between the supra-permafrost water flow and soil-water-heat at the slope scale. Using the variation of soil temperature in an active layer,the soil moisture and the supra-permafrost water flow are divided into four different phases based on the freeze-thaw action,including the frozen stability,the rapid thawing,the thawing stability,and the rapid frozen.(2) Rainfall infiltration is regarded as the main driving force of soil hydrological processes in an active layer on the slope scale,as well as the freeze-thaw action in an active layer in which both are taken into account as major factors,imposing limitations. Due to the effect of freeze-thaw process in active layers,the precipitation in the freeze period decreases. In addition,due to the soil freezing,the soil water storage capacity reduces. Moreover,the soil water infiltration stops as well as the slope lateral flow diminish. Therefore,the soil moisture and the supra-permafrost water flow are regarded in a downward trend. Furthermore,the precipitation in the thaw period and the soil water storage capacity,due to the thawing of the soil,will eventually increases. It should be mentioned that the soil water infiltration and slope lateral flow increase; consequently,the soil moisture and the supra-permafrost water flow are taken into account in an upward trend.(3) The thickness of an active layer on the upslope is higher than that one on the downslope because of the effect of terrain slope,leading to changing the freeze-thaw action on the upslope which its rate is higher than that one on the downslope. Additionally,the variation of the soil moisture and the supra-permafrost water flow on the upslope is higher than that one on the downslope. Consequently,the soil moisture content on the upslope is lower than that one on the downslope,while the supra-permafrost water flow on the downslope is relatively stable.
引文
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