The following benefits of monitoring deterioration have been presented in a detailed document: "Deterioration and Inspection of Water Distribution Systems", September 2002,  prepared by the Federation of Canadian Municipalities (FCM) and the National Research Council (NRC). This document falls under the broader umbrella of the "National Guide to Sustainable Municipal Infrastructure: Innovations and Best Practices."

1. Maintaining water quality.
2. Improving or enhancing maintenance and capital planning.
3. Identifying urgent repair and replacement needs.
4. Updating the system condition inventory.
5. Facilitating strategic planning and cost-effective inspection.
6. Providing input to risk analyses.
7. Facilitating asset management programs.
8. Showing due diligence.
9. Providing input to design standards and construction specifications.
10. Minimizing energy input requirements in the North.
11. Improving asset planning and prioritization of non-critical mains.
12. Facilitating risk management of critical mains.
13. Allowing lifetime prediction of water assets for asset management.
14. Providing feedback on manufacturing and installation problems.

Editor's Note: The above is consistent with managing the maintenance of such systems intelligently and efficiently, under the constraints of limited resources and increased maintenance needs as systems age. Furthermore, the important aspects of learning from previous problems and incorporating these lessons into new designs and practices is covered (useful for avoiding the corrosion cycle).  

Links:

What is corrosion monitoring

Why monitor corrosion

Corrosion Cycle