The steps below will show how to open an existing project that has already been associated with a ArcMap or ArcGIS Pro file. In order to integrate with ArcGIS Pro, you will need WaterGEMS version 10.03.02.75 or later and SewerGEMS version 10.03.03.44 or later. The examples below use WaterGEMS as an example, but the general workflow will be the same.
If you are opening the APRX file in WaterGEMS for ArcGIS Pro, the WaterGEMS model file should automatically open as well, with no additional steps required. If there is no model file associated with the ArcGIS Pro project file and you are working in WaterGEMS for ArcGIS Pro, you will be able to import new or existing WaterGEMS models.
After opening WaterGEMS for ArcMap, click the WaterGEMS menu, choose View > Hydraulic Model Manger (or Project Manager)
In the Hydraulic Model Manager or Project Manager window, highlight the project name, then click the second icon on top that looks like a folder opening to open the WaterGEMS model.
After you do this you will notice the project folder in the Project Manager window will switch from grey to blue and it will have a red check mark on it showing the project is now open. Now you can continue editing or performing calculations on your model as necessary.
WaterGEMS for ArcMap and WaterGEMS for ArcGIS Pro FAQ
SewerGEMS for ArcMap and SewerGEMS for ArcGIS Pro FAQ