Preferential flow (PF) is a fundamentally important soil hydrologic process that controls a variety of soil physical, chemical, and biological functions. However, the lack of theory in this field and the existence of conceptual and technological bottlenecks continue to hinder the advancement in understanding and predicting PF. This paper explores three theories that link pedogenesis to flow regimes, including 1) nonequilibrium thermodynamics as applied to the open dissipative system of field soils with continuous energy and mass inputs that results in the dual-partitioning of pedogenesis into organizing and dissipating processes; 2) constructal theory that explains the tendency for dual-flow regimes in soils, one with high resistivity (Darcy flow) and the other with low resistivity (PF), together they form natural PF configuration that provides the least global flow resistance; and 3) theory of evolving networks that sheds light on diverse PF networks for increasing the efficiency or effectiveness of energy and mass transfer in the subsurface. All three theories support the notion that PF is likely universal in natural soils. However, some controversies associated with these theories require more concerted efforts to systematically test their applicability and to formulate quantitative relationships between PF occurrence and its macroscopic controls.
Lin, H.S. (2010): Linking principles of soil formation and flow regimes. Journal of Hydrology 393:3-19.. DOI: 10.1016/j.jhydrol.2010.02.013