Lecture30-33(2008) - SOIL WATER FLOW (continued) Read:...

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SOIL WATER FLOW (continued) Read : Chapter 8 Introduction to Environmental Soil Ph ysics Water flow in saturated soil is easy to evaluate and can be described with a linear equation. However, in most cases water flow in the root and vadose zone (unsaturated zone above the groundwater table) occurs under unsaturated conditions. Water flow in unsaturated soils is much more difficult to evaluate and it is not characterized by a linear equation, rather a complex nonlinear relation among the variable soil water content ( 2 v ), matric potential, and hydraulic conductivity.
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The same driving force (decreased potential) causing water flow in saturated soil produces water flow in unsaturated soil. )R p / ) L, ) H/ ) L (gradient in saturated soil) If very small values of ) H and ) L, are taken, this can be written as: ± ) H/ ) L = dH/dL and Darcy’s Law becomes- q = K(dH/dL) ± )R m / ) L (gradient in unsaturated soil) Similarly, small values of )R m and ) L, we get q = -K(d R m /dL).
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Calculus Made Simple The rate of change of y with respect of x is: dy/dx, -which is: y/ x, -when small steps are taken. You will recognize this as the slope of the line y=f(x), where f(x) means the values one get for y is dependent on the value of x.
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This note was uploaded on 08/08/2008 for the course SS 322 taught by Professor Lowery during the Spring '08 term at University of Wisconsin Colleges Online.

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Lecture30-33(2008) - SOIL WATER FLOW (continued) Read:...

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