Soil Water Processes:Chapter 3

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Soil Water ProcessesChapter 3

• Learn how soil properties influence runoff,
  infiltration and plant growth.
• Learn some of the common terms that are used to
  describe soils profiles and soil properties.
• Learn about the main processes that occur when a
  soil wets and drys.
• Learn how to quantify the amount of water that is
  stored in the soil and how this amount changes
  with time.

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Soil Texture
Figure 3.1
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Textural Triangle
Figure 3.2
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Terms

• Voids/Pores
• Saturated

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Soil Matrix
Figure 3.3
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Porosity Equation 3.3
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Volumetric Soil Water ContentEquation 3.4
Volumetric Soil Water ContentVw/Vt
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Degree of SaturationEquation 3.5
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Gravimetric Soil Water ContentEquation 3.6
Gravimetric Soil Water Contentmw/ms
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TermsBulk Density

• Mass of soil per unit volume
• Density of soil particles usually near 165 lb/ft3
  or 2.65 g/cm3
• Compare different soils

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Bulk DensityEquation 3.8
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Dry Bulk DensityEquation 3.10
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Terms

• Tension-infiltration
• Adhesion, Cohesion, Capillary, Suction Forces
• Gravity-infiltration
• Small pores vs. Large pores
• Field capacity Wilting point

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Water Retention
Figure 3.4
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Hysteresis
Figure 3.5
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Plant Response to Soil-Water Content
Figure 3.10
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Plant Available Water versus Texture
Figure 3.5
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Soil-Water Relationships
Figure 3.6
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Factors Affecting Water Movement in Soils
Fig. 3.16
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Estimating Infiltration Rates

• Empirical Methods
• Horton and Green-Ampt Equations
• Physical Based Methods
• Darcys Law
• Flow related to hydraulic gradient and soil type

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Seasonal Soil Water Balance
?SM ? P ? IR ? Q ? G ? ET
?SM is the change in soil water storage in the
soil profile P is precipitation IR is
irrigation G is percolation water ET is
evapotranspiration Q is surface runoff
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Seasonal Soil Water Balance in Ohio
Fig. 3.23
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Fig. 4.1
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Fig. 4.4
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Fig. 4.5
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Fig. 4.6
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Annual Pan Evaporation in the USA