How to modify evaporation factor from trees to forests

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Default values for the evaporation factor of trees are set to a value consistent with the placement of individual trees. This means that if an individual tree is loaded in as a singular polygon, their evaporation factor is set properly. However, when an entire forest is loaded in, the entire forest is loaded in as a singular polygon. Where a polygon representing an individual tree may have about 1m² of polygon per tree, a forest may have closer to 30m² or 40m² per tree. This means the evaporation factor would also be multiplied with a greater surface area, and the resulting evaporation would be a similar factor too great. To correct this, you can take the following steps.

Editor → Current Situation (Ribbon tab) → Buildings (Ribbon bar) → The Building to edit (Left panel)
How to change the evaporation factor for forests:
  1. Determine the forest (or larger group of trees) for which the evaporation factor should be changed.
  2. Determine the ratio of surface area to amount of trees, for example by dividing the area of the forest by the amount of trees in the forest.
  3. Select the Construction which represents the forest in the Editor.
  4. Go to the "Details" tab.
  5. Find the "Water evaporation" Function Value.
  6. Divide the "Water evaporation" value by the rato determined earlier, to get a new, lower evaporation factor.
  7. Enter that new factor as the "Water evaporation" Function Value for this forest.

Notes

  • To do this en-masse for Constructions with a tree-line function, consider modifying the Function Values of the relevant Functions instead. Note that this may mean you will want to perform the opposite operations on individual trees where appropriate.
  • If you have a GeoJSON file with data on tree density, you can combine that file with a GeoJSON file containing exported Constructions from your Project. You can use that information to calculate a new evaporation factor for all tree-like Functions, and then import that data into your Project again as update for your existing Constructions.

See also