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How to implemented drainage from tif files


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Hi,

For my master thesis I am making a groundwater model to simulated the groundwater flow from a pound to a well. There is already a model of this area but I will make hydrological layers in more detail. For my model I used the drainage of the old model. The files I have are tif files with the conductance and elevation of the drains. The cell size of the old model is the same as in the new model. But how can I use this tif files to make the drains in the new model?

I have the same problem with the rivers. I have the conductance, elevation and the stage in the tif extension but I don't know how to implemented them in GMS.

Thanks in advance

Rianne

 

 

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You could maybe read the tif file in GMS, convert the raster data to scatter data, export the data, use Excel to combine the data to points with elevation and conductance, and then copy and paste the values into a coverage.

More detailed steps:

  • Read tif into GMS by dragging and dropping the file onto GMS.
  • Convert the raster to a 2D scatter set by right clicking on the raster and selecting the Convert To | 2D Scatter menu item.
  • Export the values by right clicking on the 2D Scatter dataset, selecting the View Values menu item, and then clicking on the Export button at the bottom of the dialog.
  • Open the exported data file in Excel.
  • In GMS create a MODFLOW conceptual model with Drains turned on by right clicking in the Project Explorer and selecting the New | Conceptual Model menu item, and toggling on Drains.
  • Create a new coverage by right clicking on the conceptual model in the Project Explorer and selecting the New Coverage menu item.
  • Open the coverage attribute table by right clicking on it and selecting the Attribute Table menu item.
  • Turn on the X, Y, Z columns in the attribute table by toggling on Show coordinates.
  • Copy the X, Y columns from Excel.
  • Paste the X, Y columns into the attribute table.
  • In the All row in the attribute table change the type to Drain.
  • Copy the conductance and elevation columns from Excel.
  • Paste the the values into the attribute table.

Now the coverage can be used to map the values to MODFLOW. The same steps could be used for the river package data into a new coverage. This assumes that the raster pixels match the MODFLOW grid and that the cells without boundary conditions are masked out of the raster.

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Thanks for your help. It works in this way. I have only one problem. There are 45000 cells and I can't copied it in once because the program will crash. I can do 500 cells in once. So it takes a lot of time do this. Is there maybe another way?

I have also another question in the old model the drainage is in the middle of the model implemented with cell sizes of 5 by 5 meters. Can I implemented these cell in the same way as the other cells? Or is in this way the value of the conductance wrong.

 

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It looks like GMS takes a long time because it has to create all 45000 points at once, but if they are already made then copying and pasting in the 45000 rows of data only takes a couple of minutes. I've created a *.map file which contains a coverage with 45000 points in it for you. You can just click and drag this file into GMS and you can then drag that coverage under a MODFLOW Conceptual Model item in the Project Explorer to give it MODFLOW-type properties. After giving the coverage a Drain property, you can then copy and paste those conductance, elevelation, etc. values from Excel into the Attribute table as Bill was saying. I'll attach the file to this message, let me know if you have any trouble using it as I've explained.

I'm afraid I don't understand very well your second question. Are you saying that the raster pixels do not match the cells in the middle of the MODFLOW grid? 

 

45000pointscoverage.map.txt

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Thanks, it works! This saves my a lot of time.

For the second question I mean this: the conductance of the drainage is dependent on the area of the stream-bed (C=K*A/b). In a cell of 25 by 25 meters there are several drains and therefore the conductance is a average in a cell. The cell size of my model is also 25 by 25 meters so I don't expect problems for this part. But there is an area of 2 by 2 km in which the cell size is 5 by 5 meters. I was wondering if GMS calculated the conductance automatic when you scaled up to 25 by 25 meters in cell size.

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