The Movement of Moisture in Soil by Capillarity

Gardner, Willard

doi:10.1097/00010694-191904000-00008

Cited by 19 publications

(4 citation statements)

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“…(Buckingham, 1907, p. 27) This in fact was a revolutionary concept in Buckingham's time. Inspired by observations in fully saturated soil, in which water flow depends on the gradient of hydrostatic pressure, Gardner (1919) correctly recognized the capillary potential as capillary pressure (i.e., pressure difference between air and water immediately below the curved meniscus). Furthermore, Gardner (1920) pointed out that to be consistent with the definitions of other well-known potential functions, the capillary potential, previously defined by Buckingham as the work required to move a unit mass of water from a point in soil to a free water surface, should be redefined as "the work done by the field forces in bringing unit mass from the point in question to infinity."…”

Section: Buckingham's Capillary Potentialmentioning

confidence: 98%

Soil water potential: A historical perspective and recent breakthroughs

Luo

Zhang

et al. 2022

Vadose Zone Journal

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Soil water potential is a cornerstone in defining the thermodynamic state of soil water required to quantify phenomena such as water phase change, water movement, heat transfer, electric current, chemical transport, and mechanical stress and deformation in the earth's shallow subsurface environment. This potential has historically been conceptualized as free energy stored in a until volume of soil water. Though the concept of soil water potential has been evolving over the past 120 yr, a consensual definition is still lacking, and answers to some fundamental questions remain controversial and elusive. What are the origins and mechanisms for the free energy of soil water? Can the common mathematical expression of soil water potential as superposition of gravitational, osmotic, and matric potentials be used to define water phase transitions in soil? Are these major components of soil water potential independent or coupled? Is pore water pressure always tensile under unsaturated conditions? If so, how can soil water density be as high as 1.7 g cm −3 ? How do adsorptive soilwater interactions originating from the electromagnetic field around and within soil particles transfer to mechanical pore pressure? In this review, the authors (a) provide critical analysis of historical definitions of soil water potential to identify their strengths, limitations, and flaws; (b) synthesize the origins of electromagnetic energies in soil to clarify the fundamental differences between adsorptive and capillary soil water potential mechanisms; (c) introduce a recently emerging concept of soil matric potential that unifies contributions of adsorption and capillarity to soil water potential; and (d) illustrate the generality and promise of the unified definition of soil water potential for answering some of the fundamental questions that remain elusive to the hydrology, geoengineering, and geoscience communities.

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Section: Buckingham's Capillary Potentialmentioning

confidence: 98%

Soil water potential: A historical perspective and recent breakthroughs

Luo

Zhang

et al. 2022

Vadose Zone Journal

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“…Despite all this, Buckingham (1907) did not manage to formulate a clearcut physical-mathematical flow theory that quickly inspired other soil physicists. Gardner (1919) and Gardner and Widtsoe (1921) gave it another try, but got bogged down in details and ended up with something very special. It took a person like Richardson, with wide experience of continuum mechanical theories (fluid mechanics, theory of elasticity) to formulate a clearcut theory in a very direct manner.…”

Section: Movement Of Water In Bare Soilmentioning

confidence: 99%

The Contributions of Lewis Fry Richardson to Drainage Theory, Soil Physics, and the Soil-Plant-Atmosphere Continuum

Raats

Knight

2018

Front. Environ. Sci.

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The English polymath Lewis Fry Richardson (1881-1953) made important contributions to many fields, including numerical weather prediction, finite difference solutions of partial differential equations, turbulent flow and diffusion, fractals, and the cause and evolution of conflicts. His first papers in 1908 concerned unconfined flow of water in saturated soil, arising in the design of required ditch spacing for draining peat. He developed and used a graphical method to solve this problem. This and other practical problems stimulated his interest in numerical methods and soon led him to the challenge of numerical weather prediction. In 1922 he published the book Weather Prediction by Numerical Process. He did the research for this book under difficult circumstances just before, during, and right after World War I. The book was received positively, but methods like those proposed in it were not successfully implemented until the invention of fast digital computers around 1950. Posthumously, most of Richardson ′ s contributions in various fields received considerable attention. Important exceptions are his contributions to soil science and hydrology, on which we focus in this paper. In his 1922 book, Richardson formulated an elaborate model for transport processes in the atmosphere. For the lower boundary of his atmospheric model, he needed to understand the movement of liquid water, water vapor, and heat in the upper layer of the soil, and at the soil-atmosphere and plant-atmosphere interfaces. Finding little previous work on this, he first of all formulated the partial differential equation for transient, vertical flow of liquid water in soil. We argue that the resulting equation can rightly be called the Richardson-Richards equation. In addition he formulated equations for simultaneous transfer of liquid water and water vapor, for transfer of heat in soil, and for the balances of water and energy at the soil-atmosphere and plant-atmosphere interfaces. Finite difference versions of all the equations were incorporated in the numerical weather forecasting model. Unfortunately, his results were hardly noticed by soil physicists and hydrologists, likely because they were too effectively buried in an intimidating book on weather prediction.

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“…In contrast, the earliest definition of matric potential is dated back to 1907, when Buckingham (1907) defined the capillary potential as the work required per centigram of water to pull water away from soil and used this concept to study the water flow in soil. Later on, Gardner (1919) identified the equivalence between capillary potential and capillary pressure (Pa), that is, the pressure difference across the water‐air interface. Attempt to harness thermodynamics for a rigorous definition of water potential was missing until Edlefsen and Anderson (1943).…”

Section: Introductionmentioning

confidence: 99%

A Thermodynamic Formulation of Water Potential in Soil

Zhang

Gou

et al. 2022

Water Resources Research

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Water potential (Pa) refers to the Gibbs free energy of water per unit volume relative to free water. In soil, water is not inert to soils but instead unfailingly interacts with them, giving rise to enormous complexities in understanding soil behavior. Such interaction between soil and water is conventionally quantified via the concept of soil water potential, which is defined as the free energy change per unit volume of water when moving from the free water state to the soil water state (Noy-Meir & Ginzburg, 1967). In the past decades, soil water potential is treated as a cornerstone concept in soil physics, unsaturated soil mechanics, poromechanics, and vadose zone hydrology, and is adopted as the state variable in modeling multiphase and multiphysical processes occurring in soil and many other porous media, for example, water retention behavior (e.g.

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The Movement of Moisture in Soil by Capillarity

Cited by 19 publications

References 0 publications

Soil water potential: A historical perspective and recent breakthroughs

Soil water potential: A historical perspective and recent breakthroughs

The Contributions of Lewis Fry Richardson to Drainage Theory, Soil Physics, and the Soil-Plant-Atmosphere Continuum

A Thermodynamic Formulation of Water Potential in Soil

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