Effects of antecedent moisture and macroporosity on infiltration and water flow in frozen soil
Effects of antecedent moisture and macroporosity on infiltration and water flow in frozen soil
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DOI：
10.1002/hyp.13629
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发表时间：
2019-11-15
影响因子：
3.2
通讯作者：
Cey, Edwin
中科院分区：
文献类型：
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作者：
Pittman, Freda;Mohammed, Aaron;Cey, Edwin
冻土入渗在土壤冻融和融雪驱动的水文过程中起着重要作用。为了更好地了解冻土中复杂的热能和水分运移机制，研究了前期含水率和大孔隙度对冻土入渗的影响。冻结大孔和非大孔土柱的池塘入渗试验表明，干大孔土的入渗速率可达10(3)~10(4)mm·d(-1)，比干非大孔土高2~3个数量级。结果表明，快速渗透和排水是优先流过最初充满空气的大孔隙的结果。利用记录的流速和测量的大孔隙特征，计算表明，饱和流动和非饱和膜流的组合很可能发生在大孔隙中。在潮湿条件下，无论是否存在大孔隙，入渗都受到孔冰融化速度较慢的限制，入渗速率为2.8~5.0 mm/d(-1)。潮湿条件下优先流的减少归因于富蒙脱石粘土引起的土壤膨胀(减少了大孔隙体积)和大孔隙内的孔隙冰堵塞。相比之下，干土柱实验表明，与非大孔土壤相比，大孔隙为渗透过程中的水和热能提供了绕过冻结基质的管道，降低了融化速度。总体而言，前期含水率对冻结大孔土壤入渗和流动的起始、时间和大小起主导作用，大孔连通性起着重要作用。这项研究提供了一个重要的数据集，可以帮助开发考虑土壤冻融和优先流对寒冷地区积雪融化分配的交互影响的水文模型。
Infiltration into frozen soil plays an important role in soil freeze-thaw and snowmelt-driven hydrological processes. To better understand the complex thermal energy and water transport mechanisms involved, the influence of antecedent moisture content and macroporosity on infiltration into frozen soil was investigated. Ponded infiltration experiments on frozen macroporous and non-macroporous soil columns revealed that dry macroporous soil produced infiltration rates reaching 10(3) to 10(4) mm day(-1), two to three orders of magnitude larger than dry non-macroporous soil. Results suggest that rapid infiltration and drainage were a result of preferential flow through initially air-filled macropores. Using recorded flow rates and measured macropore characteristics, calculations indicated that a combination of both saturated flow and unsaturated film flow likely occurred within macropores. Under wet conditions, regardless of the presence of macropores, infiltration was restricted by the slow thawing rate of pore ice, producing infiltration rates of 2.8 to 5.0 mm day(-1). Reduced preferential flow under wet conditions was attributed to a combination of soil swelling, due to smectite-rich clay (that reduced macropore volume), and pore ice blockage within macropores. In comparison, dry soil column experiments demonstrated that macropores provided conduits for water and thermal energy to bypass the frozen matrix during infiltration, reducing thaw rates compared with non-macroporous soils. Overall, results showed the dominant control of antecedent moisture content on the initiation, timing, and magnitude of infiltration and flow in frozen macroporous soils, as well as the important role of macropore connectivity. The study provides an important data set that can aid the development of hydrological models that consider the interacting effects of soil freeze-thaw and preferential flow on snowmelt partitioning in cold regions.