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robinb

Stochastic modelling

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Hi

I'm just about to start my master thesis that is about modelling well-protection zones stochastically.

I will be using the stochastic modelling module for GMS/MODFLOW and the MODPATH module as well as the risk analysis wizard. I'm wondering if these modules are much more demanding than just using GMS/MODFLOW as I am thinking about investing in a new laptop.

I have been reading in on the subject and wonder if there is any more specific information about what the stochastic module can do as i have not yet recieved the license for that particular module?

I'm also wondering what the difference is between 7.1 and 8? There might be a possibility to use 8, but neither I or my professor has used it and i wonder if there is any benefits/advantages to use version 8 or will it just take time to get used to a maybe new interface?

With regards

/robinb

Edited by robinb

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It doubt doing stochastic modeling will require you to replace your laptop if you were already able to run GMS on it. While it will require more time to do obtain a full stochastic solution it is still running the same basic programs as before just switching the variables up a little bit each time. My guess is that much more memory is expended running MODFLOW in GMS than is required to keep switching the variables.

There is a summary of what the stochastic model is capable of on our wiki. You can view the summary by clicking here.

There are several differences between GMS 7.1 and GMS 8.0. The best way of getting an idea about what those differences are is once again to visit our wiki. You can see how GMS 8.0 compares to GMS 7.1 by clicking here

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Finally i've gotten the license key and started building my model. Just to make sure i don't do anything stupid when creating the boreholes. I hope it's possible to couple the stratography to the surface (so that 0 is the later added surface elevation) and it is not needed to take the surface elevation into account when creating the boreholes? I've already created around 50 holes and would like to avoid recalculating them.

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Im not sure if i'm inserting the borehole data in the right way.

How should i "end" the stratografy? To show that the borehole ends, but not indicate that there is nothing below it?

The boreholes that end in impermeable bedrock i put as material_-1. At the moment a borehole input is put like:

0.0 material_2 material_2 0

-45.0 material_4 material_4 0

-68.0 material_2 material_2 0

But the borehole ends at -80 but the stratografy doesn't. How do i indicate this?

I'm also wondering how i couple the elevation of the ground to the borehole data?

/with regards

robinb

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I found a bug (a software one) when deleting boreholes from the borehole editor. The removed borehole stays on the map but changes name to borehole(1) even though it is not longer present in the project explorer.

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Boreholes are intended to document drilling logs where the stratigraphy has been tested. If you would like to keep showing what the stratigraphy is like below the depth of a borehole, then you would have to make assumptions about what is below the hole and put these assumptions in with the borehole data.

The simplest method of making sure your boreholes line up with the surface of the ground is the horizons method. In the horizons method, rather than coupling the borehole data with the ground you use the borehole data to define the location of the ground. You can read about the Horizons method on our wiki by clicking here.

The bug you describe with boreholes continuing to display after being deleted is a known issue that should be resolved soon.

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Hi again, thanks for all the help.

Some more questions that has occured to me:

When adding the starting head, is it a must to add it to all the layers?

How can i solve "The starting head is lower than the bottom elevation in layer 1"? Maybe it has something to do with the first question?

I suspect that it is that i need to only add the starting head to the layers that is within the starting heads grasp. I have a starting head that varies greatly within the modell and i have quite a few layers in the grid. Therefore i hope there is some practical way to do this.

And "Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=1, j=90, k=1, in stress period 1."

I have read the tutorials and they have given me guidance in some other questions but I have not seen any reference to these problems and hope you can help me.

With regards,

robinb

Edited by robinb

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No, you don't have to add the starting head to all layers.

If your starting head is below the bottom elevation in the cell, it is a dry cell. If it will always remain dry, just make the cell inactive, otherwise change the starting head to be just above the bottom of the cell. You could also use cell rewetting, but that can often give you convergence problems. You would still need to designate that cell as being dry to start (with either a -888 or -999 head designation). In short, you cannot start the model by designating a head that is below the cell bottom (unless it is the dry cell head as designated by either -888 or -999).

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