[R-sig-Geo] How is defined PWP in soilgrids?

[Tomislav Hengl]

Hi Eliza,

The most up-to-date water capacity maps of the world you can find at:

https://zenodo.org/record/2629149

Soil water content in percent for 33 kPa and 1500 kPa suctions predicted 
at 6 standard depths (0, 10, 30, 60, 100 and 200 cm) at 250 m resolution 
and based on a global compilation of soil profiles (USDA NCSS, AfSPDB, 
ISRIC WISE, EGRPR, SPADE, CanNPDB, UNSODA, SWIG, HYBRAS and HydroS) you 
can access from:

https://zenodo.org/record/2784001

and visually explore at:

https://openlandmap.org/#/?base=Stamen%20(OpenStreetMap)&center=46.3848,2.4939&zoom=4&opacity=80&layer=sol_watercontent.33kPa_usda.4b1c_m&depth=0

Note these maps are not based on PTFs but on direct prediction from 
laboratory data.

If you have any more issues or questions please post them via:

https://github.com/Envirometrix/LandGISmaps

THT,

-- 
T. (Tom) Hengl
Technical support / Vice Chair
OpenGeoHub Foundation
Address: Agro Business Park 10 (unit 1.05), 6708 PW Wageningen, NL
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On 6/11/19 7:34 AM, Mª Eliza Turek wrote:
> Dear Tomislav,
> 
> I am working with SoilGrids database and I need the values for permanent 
> wilting point, because I want to define the soil water retention curve 
> with the van Genuchten equation. However, I saw that are available just 
> the available water in some potentials, and not the values of retention 
> themselves. I was thinking about use WWP as a point itself and estimate 
> the permanent wilting point with a pedotransfer function, but for that I 
> need to know the criteria for WWP. How did you define field capacity? By 
> pedotransfers?
> 
> You said in one of your answers 
> (https://groups.google.com/forum/#!topic/global-soil-information/SMJzAXBhS08) 
> that
> WWP = moisture potential at wilting point in kPa e.g. -1585 (pF 4.2),
> However in my selected data they are at the same order of magnitude that 
> AWCh1, AWCh2 and AWCh3. Is this correct?
> 
> Thank you very much!
> 
> -- 
> Maria Eliza Turek
> PhD Student - Graduate Program in Environmental Engineering  - PPGEA
> Federal University of Paraná - UFPR- Brazil