Negative Drainage Observed using 2nd Groundwater Option for Noah-MP 4.0.1

[mcthreems]

When running LIS using the 2nd groundwater option in Noah-MP 4.0.1 we found that the simulation output showed negative subsurface runoff/drainage. I have attached a figure showing the groundwater contributions from various sources, with positive values indicating a source is adding water to the column and negative values indicating a source is removing water from the column. The drainage appears to exclusively add water to the column (except where it is 0). Is this behavior expected for this groundwater option and surface scheme combination? If not, is there a likely culprit that would cause this? I have attached the ldt and lis configuration files, as well as the log file for the simulation.

ldt.config_noahmp401_1masc_42.0_-111.25.txt
lis.config_noahmp401_snake_gw2_nrdef_1masc_42.0_-111.25.txt
lislog_noahmp401_snake_gw2_nrdef_1masc_42.0_-111.25.0000.txt

[dmocko]

Hi @mcthreems

What exact variable are you plotting for drainage?

I don't know the typical hydrometeorological conditions for the location you are plotting, or the details about this scheme.

I suggest that you read the Noah-MP technical documentation on this page:
https://ral.ucar.edu/model/noah-multiparameterization-land-surface-model-noah-mp-lsm

It's for version-5.0, but it can provide details about this groundwater option. Between the technical documentation and the
original journal articles, you might get some clues as to why this is happening at your simulated location.

[mcthreems]

Thank you for your response and the link to the technical paper. We'll continue looking into this on our end and may try reaching out to people on the Noah-MP side. If we do figure it out I'll try to update this thread.

[mcthreems]

Also, regarding the variable we are describing as "drainage", it's the "Qsb" output variable.

[dmocko]

"Qsb" in the MODEL TBL file is typically defined this way:

Qsb: 1 kg/m2s OUT 1 0 0 1 234 10000 # Subsurface runoff (kg/m2s)

Note that you might be using different units.

Either way, "OUT" indicates the water is leaving the column. And by definition "Qsb" is only positive when water is leaving.

You might also consider looking at the the recharge, using these Noah-MP-specific variables in the MODEL TBL.

RechToGW:           0  m       -    1 0 0 1 148 10      # recharge to water table when groundwater is deep
RechFromGW:         0  m       -    1 0 0 1 148 10      # recharge from water table when groundwater shallow

Note the different units for these variables.

[mcthreems]

That matches our settings and understanding of Qsb. I reversed the sign for the figure since in the figure positive values indicate water entering the column. I'll add the recharge outputs to our output file to see how they look.