Introduction
to Basic Ground-Water Flow
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By
the earthDr!
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Capillary
Fringe and Soil Pore-Size Distribution in Relation to the Water Table
and Vadose Zone
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A basic
discussion dealing with soil genesis and morphology is warranted to get
a better understanding of subsurface transport. Looking at this first figure,
we see numerous soil particles of varied shape and size. This figure displays
soil particles both above and below the water table. The zone of soil above
the water table is known as the unsaturated zone or the vadose zone. Note
that the soil particles in the
No matter how tightly (densely) the soil particles are packed, there will always be void spaces between them. The void spaces between the soil particles are known as the soil pores. Below the water table the pore spaces are filled with water. Above the water table the pore spaces are filled with varied amounts of air and water. These soil pores are interconnected amongst themselves. The soil pores are analogous to water pipes. Just like waterpipes, the diameter of soil pores can vary. The diameter of soil pores range from large to small. Large pores are called macropores. Medium-size pores are called mesopores. Small pores are called micropores. In some soils, the flow of water goes primarily through the macropores. The macropores are often lined by clay minerals. This lining of clay minerals is called clay skins. This is analogous to the lining of an artery with plaque or the armoring of a stream bed with detritus. This lining or armoring of the larger soil pores limits/slows water flow or water drainage from the micropores to the macropores. Back to the capillary fringe: The capillary fringe is an interesting zone within the soil profile. Looking at the figure below, the capillary phenomenon is detailed. I remember many years ago, my skin being pricked and then, my blood flowed up a small diameter glass tube that was applied by the lab technician to the skin abrasion. The soil macropores are even smaller than the inner diameter of these capillary |
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earthDr@earthDRx.org |
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