Source tracking tracks over time what percentage of water that reached any node in the network had its origin at a specific node. The source node can be any network node, including storage nodes. Source tracing is a useful tool for analyzing distribution systems that draw water from two or more supplies. of different raw water. It can show the extent to which water from a given source mixes with other sources. sources and how the spatial pattern of this mixture changes over time. EPANET provides an automatic facility to perform source tracing. The user only needs to specify which node is the source node. Internally, EPANET treats this node as a source constant of a non-reacting constituent entering the network with a concentration of 100.