SAGA-GIS Tool Library Documentation (v9.1.2)

Tool Soil Water Capacity

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
InputSand (*)Grid, input, optionalSAND[%]-
Silt (*)Grid, input, optionalSILT[%]-
Clay (*)Grid, input, optionalCLAY[%]-
Soil Organic Carbon (*)Grid, input, optionalCORG[permille]-
Bulk Density (*)Grid, input, optionalBULK[kg/m³]-
Cation Exchange Capacity (*)Grid, input, optionalCEC[cmol/kg]-
pH (*)Grid, input, optionalPH--
OutputField CapacityGrid, outputFC--
Permanent Wilting PointGrid, outputPWP--
Water Capacity at Saturation (*)Grid, output, optionalTHETA_S--
OptionsGrid SystemGrid systemPARAMETERS_GRID_SYSTEM--
DefaultFloating pointSAND_DEFAULTdefault value if no grid has been selectedMinimum: 0.000000
Maximum: 100.000000
Default: 15.000000
DefaultFloating pointSILT_DEFAULTdefault value if no grid has been selectedMinimum: 0.000000
Maximum: 100.000000
Default: 37.000000
DefaultFloating pointCLAY_DEFAULTdefault value if no grid has been selectedMinimum: 0.000000
Maximum: 100.000000
Default: 48.000000
DefaultFloating pointCORG_DEFAULTdefault value if no grid has been selectedMinimum: 0.000000
Maximum: 1000.000000
Default: 15.000000
DefaultFloating pointBULK_DEFAULTdefault value if no grid has been selectedMinimum: 100.000000
Maximum: 2650.000000
Default: 1350.000000
DefaultFloating pointCEC_DEFAULTdefault value if no grid has been selectedMinimum: 0.000000
Default: 45.000000
DefaultFloating pointPH_DEFAULTdefault value if no grid has been selectedMinimum: 0.000000
Maximum: 14.000000
Default: 6.400000
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 27 [-SAND <str>] [-SAND_DEFAULT <double>] [-SILT <str>] [-SILT_DEFAULT <double>] [-CLAY <str>] [-CLAY_DEFAULT <double>] [-CORG <str>] [-CORG_DEFAULT <double>] [-BULK <str>] [-BULK_DEFAULT <double>] [-CEC <str>] [-CEC_DEFAULT <double>] [-PH <str>] [-PH_DEFAULT <double>] [-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
	Grid, input, optional
  -SAND_DEFAULT:<double>	Default
	Floating point
	Minimum: 0.000000
	Maximum: 100.000000
	Default: 15.000000
  -SILT:<str>           	Silt
	Grid, input, optional
  -SILT_DEFAULT:<double>	Default
	Floating point
	Minimum: 0.000000
	Maximum: 100.000000
	Default: 37.000000
  -CLAY:<str>           	Clay
	Grid, input, optional
  -CLAY_DEFAULT:<double>	Default
	Floating point
	Minimum: 0.000000
	Maximum: 100.000000
	Default: 48.000000
  -CORG:<str>           	Soil Organic Carbon
	Grid, input, optional
  -CORG_DEFAULT:<double>	Default
	Floating point
	Minimum: 0.000000
	Maximum: 1000.000000
	Default: 15.000000
  -BULK:<str>           	Bulk Density
	Grid, input, optional
  -BULK_DEFAULT:<double>	Default
	Floating point
	Minimum: 100.000000
	Maximum: 2650.000000
	Default: 1350.000000
  -CEC:<str>            	Cation Exchange Capacity
	Grid, input, optional
  -CEC_DEFAULT:<double> 	Default
	Floating point
	Minimum: 0.000000
	Default: 45.000000
  -PH:<str>             	pH
	Grid, input, optional
  -PH_DEFAULT:<double>  	Default
	Floating point
	Minimum: 0.000000
	Maximum: 14.000000
	Default: 6.400000
  -FC:<str>             	Field Capacity
	Grid, output
  -PWP:<str>            	Permanent Wilting Point
	Grid, output
  -THETA_S:<str>        	Water Capacity at Saturation
	Grid, 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