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Soil Water Processes:Chapter 3Soil Water Processes:Chapter 3
Learn how soil properties influence runoff, Learn how soil properties influence runoff, infiltration and plant growth.infiltration and plant growth.
Learn some of the common terms that are used Learn some of the common terms that are used to describe soils profiles and soil properties.to describe soils profiles and soil properties.
Learn about the main processes that occur Learn about the main processes that occur when a soil wets and drys.when a soil wets and drys.
Learn how to quantify the amount of water Learn how to quantify the amount of water that is stored in the soil and how this amount that is stored in the soil and how this amount changes with time.changes with time.
Volumetric Soil Water ContentVolumetric Soil Water ContentEquation 3.4Equation 3.4
t
wv V
Vθ
Volumetric Soil Water Content=Vw/VtVolumetric Soil Water Content=Vw/Vt
Gravimetric Soil Water ContentGravimetric Soil Water ContentEquation 3.6Equation 3.6
s
wg m
mθ
Gravimetric Soil Water Content=mGravimetric Soil Water Content=mww/m/mss
TermsTermsBulk DensityBulk Density
Mass of soil per unit volumeMass of soil per unit volume Density of soil particles usually near 165 Density of soil particles usually near 165
lb/ftlb/ft33 or 2.65 g/cm or 2.65 g/cm33
Compare different soilsCompare different soils
TermsTerms
Tension-infiltrationTension-infiltration Adhesion, Cohesion, Capillary, Suction ForcesAdhesion, Cohesion, Capillary, Suction Forces
Gravity-infiltrationGravity-infiltration Small pores vs. Large poresSmall pores vs. Large pores Field capacity & Wilting pointField capacity & Wilting point
Estimating Infiltration RatesEstimating Infiltration Rates
Empirical MethodsEmpirical Methods Horton and Green-Ampt EquationsHorton and Green-Ampt Equations
Physical Based MethodsPhysical Based Methods Darcy’s LawDarcy’s Law Flow related to hydraulic gradient and soil typeFlow related to hydraulic gradient and soil type
Seasonal Soil Water Balance
SM P IR Q G ET
SM is the change in soil water storage in the soil profileP is precipitationIR is irrigationG is percolation waterET is evapotranspirationQ is surface runoff
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