SAGA-GIS Tool Library Documentation (v9.1.2)

Tool Soil Water Capacity (Grid Collections)

This tool derives the soil water capacity for the given soil moisture potentials (psi) based on pedo-transfer functions.
Suggested psi values for field capacity estimation range between 60 hPa (pF=1.8) and 316 hPa (pF=2.5). For permanent wilting point estimation take a psi value of about 15850 hPa (pF=4.2). This tool re-implements the R-script AWCPTF by Hengl as well as the regression approach by Toth et al. (2015). See Hengl et al. (2017), Woesten & Verzandvoort (2013) and Toth et al. (2015) for more details.


References


Parameters

 NameTypeIdentifierDescriptionConstraints
InputSandGrids, inputSAND[%]-
SiltGrids, inputSILT[%]-
ClayGrids, inputCLAY[%]-
Soil Organic CarbonGrids, inputCORG[permille]-
Bulk DensityGrids, inputBULK[kg/m³]-
Cation Exchange CapacityGrids, inputCEC[cmol/kg]-
pHGrids, inputPH--
OutputField CapacityGrids, outputFC--
Permanent Wilting PointGrids, outputPWP--
Water Capacity at Saturation (*)Grids, output, optionalTHETA_S--
OptionsGrid SystemGrid systemPARAMETERS_GRID_SYSTEM--
Output UnitChoiceUNIT-Available Choices:
[0] cubic-meter per cubic-meter
[1] percentage of volume
Default: 1
Pedo-Transfer FunctionChoiceFUNCTION-Available Choices:
[0] Hodnett & Tomasella 2002
[1] Toth et al. 2015
Default: 0
Soil Moisture PotentialFloating pointPSI_FC[hPa]Minimum: 0.000000
Default: 316.000000
Soil Moisture PotentialFloating pointPSI_PWP[hPa]Minimum: 0.000000
Default: 15850.000000
AdjustmentsBooleanADJUSTSpecifies whether to correct values of textures and bulk density to avoid creating nonsensical values.Default: 1
User Defined CoefficientsBooleanUSERDEF-Default: 0
User Defined CoefficientsStatic tableCOEFFICIENTS-4 Fields:
- 1. [8 byte floating point number] ln(alpha)
- 2. [8 byte floating point number] ln(n)
- 3. [8 byte floating point number] theta s
- 4. [8 byte floating point number] theta r
(*) optional

Command-line

Usage: saga_cmd grid_analysis 28 [-SAND <str>] [-SILT <str>] [-CLAY <str>] [-CORG <str>] [-BULK <str>] [-CEC <str>] [-PH <str>] [-FC <str>] [-PWP <str>] [-THETA_S <str>] [-UNIT <str>] [-FUNCTION <str>] [-PSI_FC <double>] [-PSI_PWP <double>] [-ADJUST <str>] [-USERDEF <str>] [-COEFFICIENTS <str>]
  -SAND:<str>        	Sand
	Grids, input
  -SILT:<str>        	Silt
	Grids, input
  -CLAY:<str>        	Clay
	Grids, input
  -CORG:<str>        	Soil Organic Carbon
	Grids, input
  -BULK:<str>        	Bulk Density
	Grids, input
  -CEC:<str>         	Cation Exchange Capacity
	Grids, input
  -PH:<str>          	pH
	Grids, input
  -FC:<str>          	Field Capacity
	Grids, output
  -PWP:<str>         	Permanent Wilting Point
	Grids, output
  -THETA_S:<str>     	Water Capacity at Saturation
	Grids, output, optional
  -UNIT:<str>        	Output Unit
	Choice
	Available Choices:
	[0] cubic-meter per cubic-meter
	[1] percentage of volume
	Default: 1
  -FUNCTION:<str>    	Pedo-Transfer Function
	Choice
	Available Choices:
	[0] Hodnett & Tomasella 2002
	[1] Toth et al. 2015
	Default: 0
  -PSI_FC:<double>   	Soil Moisture Potential
	Floating point
	Minimum: 0.000000
	Default: 316.000000
  -PSI_PWP:<double>  	Soil Moisture Potential
	Floating point
	Minimum: 0.000000
	Default: 15850.000000
  -ADJUST:<str>      	Adjustments
	Boolean
	Default: 1
  -USERDEF:<str>     	User Defined Coefficients
	Boolean
	Default: 0
  -COEFFICIENTS:<str>	User Defined Coefficients
	Static table
	4 Fields:
	- 1. [8 byte floating point number] ln(alpha)
	- 2. [8 byte floating point number] ln(n)
	- 3. [8 byte floating point number] theta s
	- 4. [8 byte floating point number] theta r