Demo video on Evapotranspiration

Hi,

I have seen some old posts where a link is given to a demo video on how to apply evapotranspiration in a Feflow model. But I cannot find the video using that link anymore.
Has the video been moved to a new location?

Best regards,

Anne

Dear Anne,

The respective video was based on FEFLOW 5.x and therefore is no longer useful nowadays. Do you have a specfic question about the assignment?

Best regards,
Peter

Dear Peter,

Thank you for your answer. I just wanted to have an idea of how to apply evapotranspiration on a model setup. Is it just to apply a fluid-flux BC on the nodes in fx. the upper 1 m of the domain and then use the equation editor to define how the flux depends on fx. the model calculated saturation?

Best regards,
Ane

Dear Anne,
If you would like to apply an expression for the outflow flux, you can only do it by means of a material property named "Sink/Source" (or Inflow/Outflow on top/bottom for 3D models). If the model is transient for flow, you can simply make a right-click on the parameter name and activate the expression editor. In such a manner, the fluid-flux BC is free for other purposes such as recharge.
Regards,
Carlos

Unfortunately, Carlos is correct. Version 6, and earlier versions of FEFLOW, allow a "parameter expression" on elemental properties only, two of which are actually boundary conditions (in/outflow on top/bottom and source/sink). Recharge could be used to simulate ET if your model can be set up to simulate ET (negative recharge) only in layer one. Otherwise, you would have to use the source/sink "material" but this is further complicated by its odd units: your parameter expression would have to account for the control volume associated with this "material" (which could be specified and accessed via an elemental user data distribution).

I once tried doing something similar using a parameter expression on source/sink and it did not work so well, which leads me to think that simulating ET this way might not work so well except in simple cases.

There are no "parameter expressions" available for "Boundary Conditions (BC)"

Another solution, which would probably work well, would be to program an IFM module to handle ET using flux or well nodes (well nodes would be easiest). Let me know if you want help with such an approach.

I think the ET video would still be applicable, but the URL is broken and has not been fixed.

Pete

Here's the old video. The swf file in the zip archive can be opened by any web browser.

Thank you Carlos and Pete for your answers, and to Peter for the video. I will have a look at it and see if I can get one of your suggestions to work. If not I will get back to you.

Regards,
Anne

Hi.

I am trying to calculate the evapotranspiration from a shallow aquifer, but I am not getting good results.

As a first attempt, I am applying a linear function using the "Expression editor" in "inflow/outflow on top/bottom" to consider water depth. In order to do this, the outflow function is conditioned to "Hydraulic Head" and "Elevation Information".

Do you have some tutorial or video that can help me to deal with it? Or some example file?

Unfortunately, the video from preview version didn't help me that much. 

Best regards,

Could you please provide the mathematical dependencies by means of an equation? If the math you are interested in is clear for me, I may assist you with a workflow.

Dear Björn Kaiser,

thank you for your support.

The expression used is presented in the picture attached.

where 2.64 mm/day is the evapotranspiration rate when the water table is reaching the top of the aquifer/surface, and considering that evapotranspiration process acts over the aquifer only until the 2 m water depth (from the top of the aquifer/surface).

If I wasn't clear enough, please, let me know.

Best regards,

Best regards,

You need to address the nodes of the first slice. Under the assumption that the head located at Slice 1 represents the water level you may implement the attached schematic expression in your more complex expression. Please also note the units in the Expression Editor.

Dear Björn Kaiser,

I didn't understand the expression into brackets. I read about the meaning of nodes parameters you used, but I couldn't understand how this expression address the nodes of the first slice. Could you help us?

Best regards,

I believe that the bracket refers to an if, then ...else sentence. In feflow expression builder you can select "if" and it gives you the structure.

Christian

Hi,

I am still having some difficulties to calculate evapotranspiration in my model, and I would appreciate a lot if someone could help me with this issue.

For calculating evaporation, if I am using an expression that depends of water level, when simulation is running, does  the software recalculate the evaporation rate each time step using the current water level information? I am implementing it using an expression on In/outflow on top/bottom, but it seems it considers only the initial water level for the whole period. How can I fix it?

Regards,

Barbara,
There are two ways of applying an expression. One is for calculating a time-constant parameter (in the Editor toolbar), the other one for applying an expression at run-time. The latter can be found via the context menu of the corresponding parameter (In/outflow on top/bottom) in the Data panel.
Please note that during the simulation as well as in the DAC file currently the calculated and applied parameter values are not visible in the view.
Best regards,
Peter

Hi Peter,

thank you very much for your answer. It was very helpful!!

I noted what you said about the values not being visible, but just to be sure, there isn't any way to access the calculated parameter values (In/outflow on top/bottom) for each time step?

If I used In/outflow for evaporation, how can I assign recharge??