Workflow if then to select Approver

Within our organization are three departments:  Dept 1, 2, and 3.  These three departments will use the same workflow.

However, when an employee sends a document for approval and selects Dept 1 in the metadata.  I would like the approver to be the Manager of Dept 1.  The same goes for Dept 2 and 3.

I'm trying to come up with a workflow that can do this.  One option I could do is to create 3 separate workflows.  However, all three will follow the same process and the only difference is the approver.  I'm trying not to have 3 workflows to update every time there is a change in the process.

What is the best way to implement this?