Joining river reaches to improve model accuracy

Effectively calculating the flows and water levels within a river is key to better accuracy. One way to account for additional water entering a main river reach is to model tributaries. Reaches can be joined using an Open Junction node to effectively represent all the flows and water levels within the river.


To join two river reaches:

  1. In the 1D River Network table, select the River Section in your main river reach located where the tributary will join. Right-click and select Copy.

  2. In the 1D River Network table, select the node at the most downstream end of the tributary. Right-click and select Paste. Label this new node (for example TribDS).

  3. Repeat step 1 above.

  4. In the 1D River Network table, select the node in the main reach immediately upstream of where the tributary will join. Right-click and select Paste. Label this new node (for example MainDS)

  5. In both of the new nodes TribDS and MainDS, set the Distance to Next = 0.

  6. In the 1D River Build tab, click on the Junction dropdown and select Open Junction. Click on the Map view to add this where the reaches join.

  7. Provide the node labels of both new nodes TribDS and MainDS, and the River Section where the tributary joins, as labels 1, 2 and 3. These can be provided in any order.

  8. To the pop-up asking if you would like to connect to these nodes, click Yes.

  9. Your tributary is now joined to your main river reach. Make sure you save the adjusted river network!

Example data files


Watch how it’s done!