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Soil water movement (Hydraulic Conductivity (Unsaturated water flow (under…
Soil water movement
Hydraulic Conductivity
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Soils with low K have poor drainage and use is usually restricted to shallow-rooting or wet-adapted plants - e.g. wetlands or gley soils
Soils with low K will flood more easily - careful irrigation management needed, particularly with effluent application
Pouiselle's Law
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Macropores (pores with a diameter > 30um) will have a large effect on water movement through a saturated soil
An increase in radius by an order of magnitude results in an increase in flow rate by a factor of 10000
Tortuosity
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Water flow in pores is restricted by constrictions, connections and dead ends
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Darcy's Law
The flux (discharge rate/unit area) is proportional to the hydraulic gradient (pressure drop per unit distance) and a constant K which describes the ability of the medium to transmit water
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Increase in hydraulic graduent gives an increase in flux, K always constant for a soil (assuming no change in pores)
q=flux, Q=discharge,A=area, dH/L=hydraulic gradient, K=conductivity
At low suctions, K of sandy soil > clay
At high suctions, K of clay soil> sand - clay has more smaller pores capable of flowing
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