Hello together,
I am working with a new ecohydrological model (medfate, available as a r-package) and stumbled upon the unit of mmol⋅s−1⋅m−1⋅MPa−1 for saturated soil conductivity. For my other models, I have soils that are already parameterized for their MvG values and hydraulic condunctivity, hoewever theresaturated soil conductivity is in cm/day. Can anyone advise me how to calculate between these units?
Best regards
Alexander
Hi Alexander, I cannot give you a straight answer because I am not familiar with the model but maybe the following thoughts will help you.
It is in did a strange way to express soil conductivity. At the first glance it looks like this unit is expressed as an extrinsec property. Loosely speaking this means that it is dependent on external factors, in this case you have conductivity per unit length and unit pressure change.
The first part of the units is fine mmol / s is just "mass / time". With the help of density it turns into "volume / time" and since this volume is flowing through a defined cross section area then it turns into "length / time".
--> Vol ≈18 cm^3/ mol for pure water
The question is then limited to the "external factors", in this case a unit lenght and unit pressure change. While searching for the model on the internet I found this page:
https://www.rdocumentation.org/packages/medfate/versions/2.9.3/topics/hydraulics_scalingconductance
The unit is apparently used with other variables. Look for xylemConductivity where it is stated "...conductivity per lenght of conduit and pressure drop"...more or less what I stated before.
Therefore in order to transform you first need to factor in:
Please be aware that I have come up with this after a quick search and not being familiar with the model and having only very shallow knowledge of the specific subject, so take my words carefully.
Hi Rana, would it be possible for you to explain where this conversion factor comes from?
To convert between different units of saturated soil conductivity, you can use the following conversion factors:
1 mmol⋅s−1⋅m−1⋅MPa−1 = 1.012 × 10−12 cm/day
So, to convert from mmol⋅s−1⋅m−1⋅MPa−1 to cm/day, you would multiply by 1.012 × 10−12. For instant , if the saturated soil conductivity is 10 mmol⋅s−1⋅m−1⋅MPa−1, then the equivalent value in cm/day is 1.012 × 10−11 cm/day.
So use carefully the steps as the above examples
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