Comment by saltcured

Because other replies aren't really stating it explicitly, let me add...

The water and power utilities are themselves large distributed systems. They need communications between elements just to function properly. They don't exist in a single location where people can go locally manage them in some air-gapped, offline fashion.

There is no option of not having a communication network to monitor and manage these geographically distributed elements. The question is which communication network you would use, and how you would secure it. Whether it is telephones, radio links, or people running around as messengers, it is still a communications network.

Will some "dedicated" network be any safer? If anything, I imagine the fantasy of a private network will lead to even less security. You cannot physically secure the entire signal path. You really need to treat it as untrusted and build your security on top with encryption, authentication, authorization, etc.