Preferential flow, a major influence in unsaturated soil and rock almost everywhere, occurs by multiple phenomenologically distinct hydraulic processes. For the mode known as funneled flow, concentrated in particularly conductive portions of the medium, the surface‐tension/viscous‐flow processes of traditional unsaturated flow theory predominate. Fingered flow, through conductive paths of higher water content than surrounding material, requires amendments to traditional theory concerning instabilities and dynamic flow‐regime boundaries. Macropore flow, the most recognized preferential flow mode, poses unanswered questions and major difficulties in practice. Accumulated evidence shows that water flows preferentially mostly through macropores that are (a) only partially filled with water, and (b) surrounded by matrix material that is drier, sometimes much drier, than saturation. With partial filling, geometric characteristics such as aperture have much less influence than was previously thought, and the intra‐macropore configuration of the flowing water phase, about which little is conclusively known, is then a dominant controlling influence. With unsaturated surroundings, macropore/matrix exchange interactions control, for given input and medium, the initiating circumstances, conveyed flux, and duration of macropore flow. The multiple processes in play during such interactions have different sensitivities to the matrix water state and different directions of influence. The net influence of matrix water content on macropore flow is thus highly complex and a major research need. Additional high‐priority topics are: flowpath connectivity, for watersheds as well as small scales; intra‐macropore processes, to discern their importance and possible means of quantification; and the identification of measurable soil and rock properties that can be utilized predictively.

中文翻译：

---

非饱和区优先流动过程

优先流动是在几乎所有地方的非饱和土壤和岩石中的主要影响，它是由多种现象学上不同的水力过程产生的。对于集中在介质特别是导电部分的漏斗流模式，传统不饱和流理论的表面张力/粘滞流过程占主导地位。通过比周围物质含水量更高的导电路径的指流，需要对有关不稳定性和动态流态边界的传统理论进行修正。大孔流动是最公认的优先流动模式，带来了未解决的问题和实践中的主要困难。积累的证据表明，水优先流过大孔隙，这些大孔隙（a）仅部分充满水，并且（b）被干燥的基质材料包围，有时比饱和要干燥得多。通过部分填充，孔径等几何特征的影响比以前认为的要小得多，而流动水相的大孔内构型（对此知之甚少）则成为主要的控制影响。在不饱和的环境下，对于给定的输入和介质，大孔/基质交换相互作用控制着起始条件，输送通量和大孔流动的持续时间。在这种相互作用过程中进行的多个过程对基质水状态的敏感性不同，影响的方向也不同。因此，基质含水量对大孔流动的净影响是非常复杂的，是一项重大的研究需求。其他优先事项包括：流域连通性，适用于小流域和小规模；大孔内过程，以识别其重要性和可能的​​量化手段；以及可预测地利用的可测量土壤和岩石特性的识别。