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Using GMS's Evapotranspiration package (EVT1)

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I am trying to use the Evapotranspiration (EVT1) package available in GMS 8.0 to simulate groundwater evapotranspiration in certain areas of a model domain where the water-table is close to the ground surface. To this end, I have created a coverage (using the conceptual model approach) and selected the three following areal properties: Max ET rate, ET elev. and ET extinction depth. From the GMS dialog available for this package, I seem to understand that only a constant value can be set for the ET elev. parameter.

However, I am wondering if there is a way to define a range of ET elev. values based on for example a topographic surface, rather than a constant value? The reason for this is that I have so far created only one single area in the model over which I want to simulate ET. Yet, significant topographic gradient occur over this region of the model domain, implying that I need to define several ET elev.

Any suggestions?



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Thanks for your reply Sean.

As it turns out, by using a polygon in the map module to assign ET, one can only specifiy either a constant (or time series) value for the ET elevation parameter.

Here is a step-by-step solution that was provided to me which worked perfectly fine:

  1. Set up your ET conceptual model and assign your max ET rate and extinction depth using the polygons. Map the values to the MODFLOW grid. (it sounds like you already know how to do this). Ignore the ET elevation for now.
  2. Create a “matching 2D grid” by selecting the Grid|Grid->2D Grid command in the 3D Grid Module.
  3. Go to the 2D Scatter Point module, select your 2D scatter point set representing your ground surface elevations and interpolate to the 2D Grid using the Interpolation|Interpolate->2D Grid command.
  4. Go to the ET Package dialog in the MODFLOW interface and select the ET Surface array. Select the 2D Data Set -> Array button and select the 2D data set you created by interpolation.


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