Diffusion

  • Cornelis B. Vreugdenhil

Abstract

Consider the flow of groundwater in a more or less horizontal porous layer of soil (Fig. 7.1). The mass balance for a column of soil is similar to that for a river:
$$\frac{{\partial a}}{{\partial t}} + \frac{\partial }{{\partial x}}\left( {au} \right) = w/n$$
(7.1)
where
$$\begin{array}{*{20}{c}} {a = thickness\;of\,the\,water\,layer\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\ {u = flow\,velocity\,averaged\,over\,the\,layer\,\,\,\,\,\,} \\ {w = ra\inf all\,in\,volume\,per\,unit\,surface\,area} \\ {n = porosity\,of\,the\,soil\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \end{array}$$
It has been assumed that rainfall reaches the groundwater layer very quickly; temporary storage in the unsaturated soil above the groundwater layer is not taken into account.

Keywords

Permeability Porosity 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1989

Authors and Affiliations

  • Cornelis B. Vreugdenhil
    • 1
  1. 1.ENR Computer Services for TechnologyPettenThe Netherlands

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