This document explains various options for preserving your Google Apps data. The options available vary by application -- some suggestions work better than others for a particular app, so you should make sure to test the back up capabilities of the Google App you are working with. The information below is intended as a guideline, as features provided by Google are subject to change.
Google Takeout allows you to export data from several different apps, including Google Drive, Google Contacts, and Google Reader. Google Sites is not included. See the following for instructions: UW-Madison G Suite - Export Data Using Google Takeout
In order to backup data in UW-Madison Google Sites, it must be transferred off of the UW domain. Click here for instructions.
Note that any changes made to the UW-Madison G Suite Site after this procedure will not be reflected in the personal Google Account Site or in the downloaded data so these directions would have to be repeated each time a new change is made.