WMS:MODRAT Numbering the Tree

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For MODRAT to properly compute the flow rates in a watershed, basins and reaches must be numbered and lettered properly, from most upstream to downstream. WMS will automatically number and letter the watershed components once a topological tree has been created. Choosing Number Tree from the MODRAT menu will initiate the process to number and letter the watershed model.

The numbering/lettering will start at the most upstream point of the watershed and continue automatically until a confluence point with sub-basins attached is encountered. At this point, WMS cannot determine which lateral the sub-basin drains into. Thus, a prompt will ask to select the sub-basins corresponding to each lateral that confluences at the point in question. The confluence point in question will be highlighted and WMS zooms to a window which encompasses the confluence point and all drainage basins and outlet points attached to the confluence point. Select the basins corresponding to each lateral as prompted to do so in the dialog. Note that WMS will automatically skip numbers/letters at certain confluences to allow for multiple line confluence nodes.

Helpful tips when numbering:

  • WMS will select the upstream end of the longest branch and start the numbering there by default. However, it is possible to select the upstream basin of any branch, then select the Number Tree command to designate the main line (A).
  • Use the mouse wheel to zoom in/out on the selected confluence point
  • It is not necessary to select a sub-basin for all laterals, just select Done without selecting any basins

If the renumbering results are not what was wanted, choose the Number Tree command again and try something different. If it is not possible to achieve the numbering/lettering with the automatic process, edit the Location and Lateral of each watershed component in the Edit MODRAT Parameters dialog.

Inserting Tree Spacing

WMS will update all location numbers by multiplying them by the scaling factor in order to create node spacing. This is useful for creating space in the model for inserting tree nodes in the future. Automatic tree renumbering may be a more effective method of obtaining similar results.

Renumbering the Tree

MODRAT Renumber dialog
Adding Tree Items 
After the tree has been initially numbered, WMS displays the default location and lateral every time a new basin, reach, or diversion is added. Change the location and lateral if the default values are not correct and select OK to add the tree item and automatically renumber the tree. If adding a basin at a confluence point, the default location number will be updated based on the lateral entered.
Deleting Tree Items 
The tree is renumbered when a basin or diversion is deleted. If a reach is deleted, it will be necessary to number the entire tree again if wanting to update the location numbers and laterals for each tree node.
Renumbering automatically occurs when editing the Location or Lateral in the Edit MODRAT Parameters dialog.

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