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根据优先流发展过程中所表现出来的阶段性特征和分形特征,建立了描述非均匀土壤水流运动和溶质运移过程的两区-两阶段模型。模型认为,研究区域可划分为水流经过的活动流场(即优先流流场)和水流绕过的不活动流场两个区域;优先流流场在发展过程中将先后经历流场扩张和保持两个阶段;处于扩张阶段的优先流流场,其内部土壤水流运动的快速非平衡特征明显,并表现出明显的分形特征;处于保持阶段的优先流流场,其内部的土壤水流运动类似于基质流运动,无明显的分形特征。通过在砂土、壤土和黏土条件下开展的6个示踪试验,检验和评价两区-两阶段模型、活动流场模型和两区模型模拟预测非均匀土壤水流运动和溶质运移的有效性。研究结果表明,两区-两阶段模型可较好地描述各种土质条件下的优先流运动;活动流场模型对壤土和黏土条件下的优先流运动预测精度较好,而对砂土条件下的优先流预测精度较差;两区模型对各种土质条件下的优先流运动预测精度均较差。
According to the characteristics of periodicity and fractal presented during the development of priority flow, a two-zone-two-stage model describing the process of heterogeneous soil water flow and solute transport was established. According to the model, the study area can be divided into two regions: the active flow field (ie, the priority flow field) and the inactive flow field around which the water flows, and the priority flow field will successively undergo the expansion and retention of the flow field Two phases. In the preferential flow field during the expansion phase, the rapid non-equilibrium characteristics of soil water flow in the interior are obvious and show obvious fractal characteristics. In the preferential flow field during the maintenance phase, the internal soil water flow motion is similar to Matrix flow movement, no obvious fractal features. Two tracing tests conducted under sand, loam and clay conditions were used to test and evaluate the validity of the two-zone two-stage model, the active flow field model and the two-zone model to predict inhomogeneous soil water flow movement and solute transport . The results show that the two-stage and two-stage models can describe the preferential flow motion under various soil conditions well. The preferential flow motion prediction accuracy of the active flow field model under loam and clay conditions is better, while under the sand condition The prediction accuracy of the priority flow in all the soil conditions is poor.