<p>Okay Water Holding Capacity(WHC) is how much water the soil has in it at total saturation, if you filled every soil pore space completely with water.</p>

<p>Field Capacity(FC), if I remember correctly from first year, is shorthand for the water that stays in the soil after surface runoff and groundflow has ceased; the sub-saturation "ground state" of the moist soil if you will.</p>

<p>Soil Water(SW) would appear based on the excerpt provided to be referring to the percentage of WHC present at time of measurement.</p>

<p>You've also asked about Total Available Water Capacity(TAWC) which is the water that can be accessed by plants, this is the water stored in macro, as opposed to micro, pores in the soil (it's more complex than that but we always worked it as a two grade problem; pores big enough for plant roots and pores too small for them). Usually to quantify this figure WHC, or FC depending on what's of interest, is multipled by the percentage of plant accessible pore spaces in the soil, this gives the volume of water plants can access before they start to wilt.</p>

<p>Please note I'm mostly working from my memory of an entry level class I took nearly a decade ago so this may not be perfect, but it it does check against the research material I quickly skimmed while writing.</p>

CC BY-SA 4.0
2018-06-05T18:22:44.287Z
@Universal_learner TAWC < WHC, always, there is _always_ some water in any soil that isn't plant accessible, the sandier the soil is the more closely TAWC approaches WHC, also the lower FC becomes, but even pure sand holds some water plants can't extract.
Ash
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2018-06-06T22:37:29.607Z
Makes me wonder why they don't use porosity or connected porosity instead of WHC
haresfur
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2018-06-10T15:17:32.907Z
@haresfur WHC is easier to establish experimentally, you can use direct measurements on extracted samples in the lab; porosity can only be extrapolated.
Ash
CC BY-SA 4.0
2018-06-05T16:56:39.653Z
2018-06-05T16:56:39.653Z
Ash
<p>I am reading the paper <a href="https://www.dropbox.com/s/mc8lipg08uxgzez/Characterization%20of%20yield%20reduction%20in%20Ethiopia%20using%20a%20GIS%20based%20crop%20water%20balance%20model.pdf?dl=0" rel="nofollow noreferrer">Characterization of yield reduction in Ethiopia using a GIS-based crop water balance model</a> by Gabriel B. Senay and James Verdin, and it says on page 3:</p>

<blockquote>
  <p>Soil water content (SW) is estimated through a simple mass
  balance equation where the total volume is defined by the water
  holding capacity (WHC) of the soil. SW is the amount of soil
  water present at a given time step. The value of SW varies from
  a minimum of 0 to a maximum equal to WHC (in mm)</p>
</blockquote>

<p>What is the WHC here? Is it the <em>Field capacity</em> or <em>Field Capacity - Wilting Point</em>?</p>

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2018-06-05T20:17:47.340Z
Please look at how your question looks now. Next question, you make it look good yourself, OK ;-) If you click [edit] you see the formatting. BTW Is that your personal Dropbox link? Does that mean the document can disappear? Is there no copyright issue placing it there?
Jan Doggen
<soil><soil-moisture>
What is the difference between Water Holding Capacity, Field Capacity and TAWC?
89_Simple
# What is the difference between Water Holding Capacity, Field Capacity and TAWC?

(Asked by: username_0 on 2018-06-05)

I am reading the paper [Characterization of yield reduction in Ethiopia using a GIS-based crop water balance model](https://www.dropbox.com/s/mc8lipg08uxgzez/Characterization%20of%20yield%20reduction%20in%20Ethiopia%20using%20a%20GIS%20based%20crop%20water%20balance%20model.pdf?dl=0) by Gabriel B. Senay and James Verdin, and it says on page 3:

> Soil water content (SW) is estimated through a simple mass
> balance equation where the total volume is defined by the water
> holding capacity (WHC) of the soil. SW is the amount of soil
> water present at a given time step. The value of SW varies from
> a minimum of 0 to a maximum equal to WHC (in mm)

What is the WHC here? Is it the *Field capacity* or *Field Capacity - Wilting Point*?

**Tags:** soil, soil-moisture

> **Comments:**
> **username_1**: Please look at how your question looks now. Next question, you make it look good yourself, OK ;-) If you click [edit] you see the formatting. BTW Is that your personal Dropbox link? Does that mean the document can disappear? Is there no copyright issue placing it there?  

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## 1 answers

### Answer by username_2 on 2018-06-05. Score: 3 | Accepted answer

Okay Water Holding Capacity(WHC) is how much water the soil has in it at total saturation, if you filled every soil pore space completely with water.

Field Capacity(FC), if I remember correctly from first year, is shorthand for the water that stays in the soil after surface runoff and groundflow has ceased; the sub-saturation "ground state" of the moist soil if you will.

Soil Water(SW) would appear based on the excerpt provided to be referring to the percentage of WHC present at time of measurement.

You've also asked about Total Available Water Capacity(TAWC) which is the water that can be accessed by plants, this is the water stored in macro, as opposed to micro, pores in the soil (it's more complex than that but we always worked it as a two grade problem; pores big enough for plant roots and pores too small for them). Usually to quantify this figure WHC, or FC depending on what's of interest, is multipled by the percentage of plant accessible pore spaces in the soil, this gives the volume of water plants can access before they start to wilt.

Please note I'm mostly working from my memory of an entry level class I took nearly a decade ago so this may not be perfect, but it it does check against the research material I quickly skimmed while writing.

> **Comments:**
> **username_2**: @Universal_learner TAWC < WHC, always, there is _always_ some water in any soil that isn't plant accessible, the sandier the soil is the more closely TAWC approaches WHC, also the lower FC becomes, but even pure sand holds some water plants can't extract.  
> **username_3**: Makes me wonder why they don't use porosity or connected porosity instead of WHC  
> **username_2**: @username_3 WHC is easier to establish experimentally, you can use direct measurements on extracted samples in the lab; porosity can only be extrapolated.  

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