WaterTables

[sme016]

What happened?

I don't think the WaterTable manager in this simulation attached is working properly, as:

1. I don't really know which is the correct variable to report for depth from the surface to the top of the watertable.
2. When I try to do so, it doesn't report as the 1.8 m I thought I set.
3. Drainage goes to very high values, even if SWCON is set to zero at the bottom of the profile, and I don't think there is lateral drainage in this simulation. So the water fluxes graph and water balance calculations need to account better for the water table. Shouldn't we expecct no watertable fluxes (in or out) except as water uptake by roots or as upward 'flow' as a capillary fringe.

Can you please add a working version of thisWaterTableManager tool to the Management toolbox, and indicate which variable to report.

Adequately simulating watertables is very important for many forest plantation simulations (i.e. Eucalyptus or Pinus modelling).

Also in some cases, nitrate is present in that watertable at a near constant concentrations, as I have used, or perhaps as slowly changing concentrations in some cases. A problem in the simulations is, I think, that nitrate in the watertable denitrfies. So, periodically nitrate has to be added to approximate a stable concentration. In reality, nitrate would not denitrify from a watertable if no available carbon was present, which is the case in the unconfined aquifer in the Mount Gambier region, for example. So that nitrate concentration is stable and is probably available to plants if roots grow down and reach it.

Can this NO3 tool also be improved and added to the Management toolbox?

SimsWTNO3.zip

What Operating System are you on?

Windows

[par456]

I don't really know which is the correct variable to report for depth from the surface to the top of the watertable. When I try to do so, it doesn't report as the 1.8 m I thought I set.

You are setting and reading the right variable, but between the manager script running and the report fetching the value, it is being changed from 1800 to 2200 in the daily DoSoilWaterMovement, more specifically line 566 in WaterBalance.cs with MoveDown Flux.

I might need someone more familiar with the water flow system to help out here, I'm not sure how the watertable and soil water values should be interacting.

[sme016]

Neil Huth helped me previously with this. I think he wrote the tool, but I don't think it was straight forward for him either. Dean would probably also be good help.

---

From: Andrew Paroz @.> Sent: Friday, May 3, 2024 12:14:29 AM To: APSIMInitiative/ApsimX @.> Cc: Smethurst, Philip (Environment, Sandy Bay) @.>; Author @.> Subject: Re: [APSIMInitiative/ApsimX] WaterTables (Issue #8834)

I don't really know which is the correct variable to report for depth from the surface to the top of the watertable. When I try to do so, it doesn't report as the 1.8 m I thought I set.

You are setting and reading the right variable, but between the manager script running and the report fetching the value, it is being changed from 1800 to 2200 in the daily DoSoilWaterMovement, more specifically line 566 in WaterBalance.cs with MoveDown Flux.

I might need someone more familiar with the water flow system to help out here, I'm not sure how the watertable and soil water values should be interacting.

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[sme016]

I notice that all these variables report the same value: [WaterBalance].WaterTableModel.Depth [SoilWater].WaterTableModel.Depth [SoilWater].WaterTable

And it depends on the drainage (SWCON) set to zero or not at the bottom of the profile. But the values reported don't match those provided as input parameters in the WaterTableManager.

[peter-devoil]

I spent a lot of time trying to understand boundary conditions and matric potentials. Never had much success and suspect my simulations were right for the wrong reasons.

[sno036]

You may be better off using SWIM if there are water tables