
Hi Debora,
The heads are interpolated at the observation points.
You can test this in a few minutes by making a test model with a single large triangular element, putting an observation point in the middle, and assigning fixed heads to the three vertices.
I don't have a reference for the interpolation method used. However, it appears that the three heads at the triangle vertices are used to define a plane, and that the head observations are then drawn off that plane (i.e. 2D linear interploation).
(see attachment)

I would love it if the server and slave set up could be edited during a PEST run.
Examples:
A new server becomes available during a long PEST run, and I'd like to use it
A server is over loaded, so I want to reduce the number of slaves it is running

As an alternative to your described lake model, you could contact DHI to obtain the lake IFM.

When using IfmCurveVaSetValues, what are acceptable values for IfmNlineColor?

Sorry, I'm talking about reference distributions under "User Data", which don't sem to have that option.

Look in the help file I linked for descriptions relating to "isochrone markers". These marks are measures of residence time along the pathline.

In the equation editor, half sided intervals such as
*E(*,*]
require both upper and lower bounds to be entered. Why? I would have thought that a boundary value would only need to be entered for the bounded side.
For example I have a function f(x)=y, but want the maximum value to be 0. I expect to use the left sided half open interval:
f(x) = y E(,0]
Should I put a dummy vale in the left hand side of the interval?
f(x) = y E(10000,0]

Yes, you can model first in 2D, but it will be simplified. You need to decide what parameters of the three layers are most appropriate to use in your 2D model.
If you decide that a simplified model isn't close enough to reality, then yes, you can add layers to make it 3D. Read this [url=http://www.feflow.info/html/help/default.htm?turl=HTMLDocuments%2Freference%2Fdialogs%2F3Dlayer_configuration.htm]http://www.feflow.info/html/help/default.htm?turl=HTMLDocuments%2Freference%2Fdialogs%2F3Dlayer_configuration.htm[/url]
You will apply the seawater variations as a varying head boundary referencing a power function. [url=http://www.feflow.info/html/help/default.htm?turl=HTMLDocuments%2Freference%2Fparameters%2Fboundaryconditions%2Fflow%2Fflow_boundary_conditions.htm]http://www.feflow.info/html/help/default.htm?turl=HTMLDocuments%2Freference%2Fparameters%2Fboundaryconditions%2Fflow%2Fflow_boundary_conditions.htm[/url]
Once you have that sorted out, you could think about adding mass transport and density dependent calculations to look at the seawater interface. Have a read of the relevant sections of the manual when you get up to that part of your modelling. But make sure you get the model geometry and hydraulics working first.

1) Run a model with no pumping for the same period. This will control for the other boundary conditions and fluxes in your model.
2) Export nodal head quantities for the time period you are interested in from both the model with wells and the model without wells
3) Use Surfer or ArcMap to create a raster map of groundwater head for each data set
4) Subtract one raster from the other
5) You now have a raster showing drawdown due to the wells

Try using pathlines
[url=http://www.feflow.info/html/help/default.htm?turl=HTMLDocuments%2Fworkflows%2Fvisualization%2Fpathlines.htm]http://www.feflow.info/html/help/default.htm?turl=HTMLDocuments%2Fworkflows%2Fvisualization%2Fpathlines.htm[/url]