• ### Re: Syntax for prior information

Dear Debora,

I have in mind different possibilities to reach your goal:

1) Define several parameter definitions with different parameter bounds. For example, you can assign bounds with a decrease in conductivity over depth.

2) If the ratio is Kx/Kz is kept over the layer, you can provide several ratios which change over depth. Here you will need to use tied parameter when you create the definitions (e.g. Kz will be tied to Kx). The parameter is computed from the initial values assigned in the FEM file. FePEST will keep this ratio over the entire optimization.

3) Use Prior Information. The syntax of Prior Information lines in FePEST follows exactly the PEST description (see PEST Manual, section 4.2.10). An example below:

PIBL PIFAC * PARNAME + ... = PIVAL WEIGHT OBGNME

where PIBL is a character variable of the Prior Information Definition, PIFAC is a factor which affects the parameter, PARNME is the parameter name, PIVAL is a real variable to define the right-side of the PI equation, WEIGHT is the weight assigned to the article of prior information in the parameter estimation process (e.g. inverse proportional to standard deviation), and OBGNME is the observation group to which the prior observation belongs.

FePEST separates the different variables in different entry boxes for better visualization, you need just to define the equation part. Let's say you have conductivity values 100, 50, 25 and 5 decreasing over depth. In FePEST you can use PI equation to suggest that conductivity needs to decrease in depth during the optimization as follows:

1.0 * log(Kxx_1) = 2.00
1.0 * log(Kxx_2) = 1.70
1.0 * log(Kxx_3) = 1.40
1.0 * log(Kxx_4) = 0.70

Notice that factor 1.0 is required. If the parameter is log-transformed, you need to indicate it in the equation.

• ### Re: water table does not replicates the topography... and it should!

Hi,

Just few comments based on the previous discussion:

1) Are you running a Richards-based model with a steady-state solution? If so, I would highly recommend to use the transient mode. It is very hard to solve the non-linearity of the Richards' Equation under a steady-state solution.

2) It seems to me that model is solving fine. The fact that you see a "second" water table at the top, it reflects the typical wetting front propagation in an unsaturated medium. Ideally over the time, if recharge decreases, you may see the movement of this "second" phreatic level down to the regional water level. If the recharge is very large, eventually you will see that model becomes completely saturated after several iterations, therefore it will reach a topography-like phreatic surface.

3) Material properties: Are you sure that such van Genuchten values correspond to the assigned conductivity? As indicated in item 2, it seems to me that water is moving very slow. A higher conductivity necessarily does mean fast water movement, if van Genuchten properties are not the adequate. So, please make double-check.

4) You may try to decrease the non-linearity by means of using the Modified Van Genuchten relationship and assuming a linear form (i.e. what you named before as "sigma").

• ### Re: Use of command line to run a simulation 20 times, varying initial conditions

Two more alternatives (in case analysis should be done varying material properties):

1) Use FePEST in the command line mode to setup a SENSAN (Sensitivity Analysis) run using PEST. Here you can define the parameter to be modified and distribute the output results in different files. It may require some time until to get into the workflow, but then it is worthy since you can have additional feedbackfrom PEST, which may help you to understand the sensitivity analysis.

2) Download the old FEFLOW-specific groundwater utilities for PEST. There is a nice routine named FMAINFEM to assign automatically material values to a FEM file directly in the windows command line. This was used in the past to run PEST with FEFLOW, now with the FePEST interface is not required anymore. Link is http://www.feflow.com/miscellaneos.html
• ### Re: No convergence in iteration loop - Steady state simulation

Sure. You need to define adequate parameters for the unsaturated flow modelling carried out by the Richards equation. This means you need an empirical model to relate saturation and negative pressure, saturation limits, etc. By the way, analogous to the residual water depth in the Phreatic approach, you will also need to setup an adequate residual saturation limit proper for the material properties.
• ### Re: Rate Budget Pending?

Hi Michael,

"Pending" means that FEFLOW cannot retrieve primary variables values to compute the budget. You just need to start the simulation.
If you save the DAC file using the Record Properties option at the simulation toolbar, you can have all the entire model results to compute any kind of budget.

Cheers,

Carlos
• ### Re: How to get hydraulic head along a cross-section at a single timepoint

There are two alternatives:

1) Create Observation Points at specific locations and connect them to the reference values. Then go to View - Chart - Hydraulic Head History and you will have the simulated and "reference" heads. Scatter plot is also available. You can find a lot of information how to add Observation Points in the Help System.

2) Export the FEFLOW simulated hydraulic heads. Simply a right-click on Hydraulic Head and the Export Data. You can export values from either all nodes or nodal selection.
• ### Re: Different simulated head for every layer?

Hi,

The slices below should be indicated as "Dependent". The "free" first slice will move according to the fluctuations of the phreatic level. Here, pressure will be always zero and FEFLOW will adjust the slice elevation to fulfill the statement. The next slices are adapted to changes of free slice.
I would recommend you to take a look on White Paper I (http://www.feflow.info/manuals.html) for further details.

Cheers,

Carlos
• ### Re: Interpolation Techniques

Dear Perl,

Personally I believe there is not an exact rule for deciding about interpolation techniques. The selection depends on many variables such as data type, data transformation, distribution of your points, geometry of domain, etc. These last two are the most critical. I think the best way is a trial-and-error approach here. You can make double-check plotting both interpolated fields and measurements at the same view.

Regards,

Carlos
• ### Re: Drawdown in Multilayer well

Hi,

FEFLOW has been tested with several benchmark exercises. One of them is the Theis' solution. You may take a look on the section 9.8.1 "[i][b]Transient Flow to a Well in a Confined and Unconfined Aquifer[/b][/i]" in the FEFLOW Book (pages 429-435).

Regards,

Carlos
• ### Re: How to editing already set Multilayered well BC

Dear Giuseppe,

Alternatively, you can edit the multilayer wells directly on the FEFLOW interface. Steps: 1) select the multilayer well, 2) go to the View Components panel, 3) activate Multilayer Well - Attributes, and 4) activate ONLY the attribute to edit.
You will notice that Editor toolbar will change to the attribute, e.g. "Rate (MLW)". Here you can just type the new value.

Two additional ways if you have several multilayer wells,

a) Use Link to Parameter (s) option in the Map panel to make the MLW assignment. Here, you can create a table (excel, text file, etc.) with all the attributes and link values to MLW. If edition is needed, you can edit your table any time (outside of FEFLOW) and then re-create the link again.

b) [b]This is the very fast option![/b] ONLY available in FEFLOW 6.2.
- Export all the values of MLW. Data panel and right-click on Multilayer Well. Here you can use a Excel file, text file, etc.