You may need to split a polyline and introduce a node into the network when resolving specific types of errors, for example a disconnection.  This would allow you to create a confluence with correct connectivity. 

  1. Start an edit session and select the split tool from the tools panel.

Edit toolbar and split tool

  1. Use the select tool to select the polyline you want to split, then use the Split tool by clicking on the polyline at the location you want to create the split.  The original polyline is deleted and replaced by two new polylines. 

Split tool

WarningThe split process will carry over any existing attribute values.  This is OK when the attribute is common to both polylines (e.g. river name) but the node information and any measurement value will be incorrect.  Splitting a polyline into 2 is altering the topology of the network.  You must re-run your network through the Extract Network Topology and write to Workspace tool to rebuild and correctly attribute the node and polyline fields in your river network.