The source ID is the ID number of the node that is the source of a river. The source is defined as the furthest point upstream from a polyline. It can be very useful for filtering data to encode the data with the source ID. Source ID is a required field if you are linking sites.

This page discusses how you would assign the source ID to a point dataset.

The method for transferring the source ID to a point dataset.

1.Create a point dataset and ensure the points are snapped to the network, you can achieve this by using this tool and have a unique numeric ID  field.

2.Run the point dataset through the Find Source of Site tool. For this tool to function you need to have attributed your network layer with catchment ID, distance to mouth and created the segment ID tables. This tool creates a dBase file called xxx_Source.dbf where xxx is the name of your site layer.

3.Add the output (the dBase file) of the Find source of site tool to ArcMap.

4.In the Table of Contents right (TOC) click on your site layer and go to Joins and Relates > Join... and complete the dialog as shown below.

Join dialog

A layer called Sites with an unique ID field called Sample ID is joined

to the output of the Find sources tool (table is called Sites_Source) with the SiteID field.

5.Open the attribute table of your site layer and you will see the find source table joined by the site ID field. You now need to transfer the sourceID field to the site layer.

6.Whilst in table view mode, click on the Table options button and select Add Field.

Table Options

7.Complete the Add Field dialog as shown below, make sure you set the field type to Long Integer.

Add Field

8.Find the SourceID field you just added, this will typically be at the end of the table with <Null> values, right click on the field header and choose Field Calculate as shown below.

Field calculator

9.Now transfer the source ID from the joined table to the field you just added using the field calculator as shown below.

Field Calculator

10.Once the values are transferred break the join to the find source table by right clicking on your site layer in the TOC and go to Joins and Relates > Remove Joins(s) > Remove all joins.