Soil Water Balance

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Soil Water Balance

• Reading Applied Hydrology Sections 4.1 and 4.2
• Topics
• Soil water properties
• Soil water flux
• Soil water balance
• Quotation for today (from Socrates) "There is
  only one good, that is knowledge there is only
  one evil, that is ignorance."Contributed by Matt
  Harold.

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Soil Particle Sizes
Table 1. Size limits (diameter in millimeters) of
soil separates in the USDA soil textural
classification system.

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Soil Texture Triangle
Source USDA Soil Survey Manual Chapter 3
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Soil Water Content
Soil Water Content
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Soil Water Flux, q
q Q/A
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Energy fluxes at Freeman Ranch
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Evaporation (mm/day)
Average 1.1 mm/day
Average 3.1 mm/day
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Soil Water Content
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Soil Water Balance at Freeman Ranch
E
P
0 cm
Net Exchange
10 cm
20 cm
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Soil Water Tension, y

• Measures the suction head of the soil water
• Like p/g in fluid mechanics but its always a
  suction (negative head)
• Three key variables in soil water movement
• Flux, q
• Water content, q
• Tension, y

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