GMS, SMS, and WMS User Forum

# Rob Virtue

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1. ## Defining River as polygon

If you have a river stage below bed level, you will get a warning but the model may still run. Unfortunately, the result will be garbage, sometimes spectacularly so. This is because the package includes the calculation stage elevation - bed elevation to calculate gradient, so then the value becomes negative. It could be solved by inserting a line of code that sets flow to zero if stage is at or below bed level, but for some reason that has never been implemented by USGS (perhaps I'm missing some consequence of doing so). I once got someone to modify an earlier version of the MODFLOW source cod
2. ## Transient Horizontal Flow Barrier (HFB) hydraulic characteristic

Is it possible in NWT for the hydraulic characteristic of an HFB to change over time? If so it would be useful to have this as a transient option, much like GHB conductance, to simulate the installation of HFBs over time and their degradation long-term.
3. ## Modflow - modpath

Arto, hydraulic conductivity determines how much volume flows through fro a given aquifer for a given area an gradient. Imagine a block of aquifer and a block of water being extruded out of the side as it flows. If the aquifer was all space (porosity of 1) a particle of water would flow through the aquifer at the same rate is is extruded out the side. If the porosity is only half (0.5) and everything else remains the same, the velocity of a particle in water in the aquifer has to flow twice as fast to keep the block of water moving out. If your porosity is 0.01 for the same K, it has to move 1
4. ## Drain Elevation Not Working

What conductance value are you using for the drain and what are the Kh & Kv of the high conductivity layers? A higher drain conductance is required to fully drain a higher conductivity layer.
5. ## Raster mapping of Drain Elevation Not Good

How are the drains mapped? If they are from arcs, the elevations will not necessarily follow the variation in topography, especially if topography is irregular and node spacing wide relative to the grid. If as a polygon, for the same reason, elevations may not match if topography is irregular and the grid and raster resolution are not similar. Solutions are : Use the automatic layer range allocation with "Auto-assign BC to one cell", so they can go into the layer below if below the top layer (if that is conceptually acceptable) If using arcs, redistribute vertices more
6. ## Extracting flow budget data from stochastic model runs

Any progress?
7. ## GDA2020

Can you please add the new Australian mapping datum, GDA2020, to the projection options.
8. ## Fonts and Icons in 10.3

In Windows 7 (and presumably other versions) , it depends on the font size selected under Control Panel\All Control Panel Items\Display.
9. ## TINs Question

Dunaj, Check under HELP>REGISTER> that you have the TIN module enabled.

I used to get this a lot but it's been a while. If it is a transient model, make sure there are no observations in the first time step (or maybe first stress period?) . This can stop the model running or the head file saving properly.
11. ## ET surface

Kirk, We had the same issue recently (18 September 2015), with the option for "2D Dataset -> Array" being greyed out, and were given this work-around from Jack at Aquaveo support. It seems to have worked. "Currently the option to use the "2D Dataset -> Array" command for U-Grids is not available, however I believe that the developers are working to implement it in future versions of GMS. I've got a possible work-around for you. This assumes that your topographic surface can be represented as a 2D scatter set or TIN. In this case right-click on your U-Grid and select 3D->2D, and then s
12. ## Errors in Model checker

Mina, I suspect you have specified head cells with the head elevation set below the base of the cell, which causes a terminal error. Use the automatic layer assignment option to ensure the elevations are set at the uppermost cell ("Auto assign to one cell") or the uppermost and all underlying cells ("Auto-assign including lower cells") where the elevation is above the base of the cell. If you are using transient heads, be aware that automatic layer assignment seems to use the elevations from the first stress period.
13. ## activate cells in coverages leaves more active cells in layer 1 than the rest

Mgozdor, This occurs if you have the "use to define model boundary (active area)" box checked in ANY coverage in addition to your activation coverage. This is a common problem at the moment, because if you select "layer range" in a coverage, it automatically checks the "..active area)" box. A bit annoying really. It will cause the activation errors whether you map the coverage to the model or not, so make sure you check ALL of your coverage.
14. ## PEST

I am having the same problem (GMS 10.0.6). It appears that PEST is looking for flow observations for DRN and CHD boundaries, even though there are no coverages with flow observations in the current model.
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