Is a rainwater cistern worthwhile for garden irrigation?

Well, with existing ground cover (mulch or wood chips) and manual irrigation with rainwater, restriction times from 8 am to 6 pm apply, I can just about imagine that as an additional rule. The question is, who enforces it?

At least manual watering can't be seen from outside the property, but a running sprinkler can. So everyone can decide for themselves whether to comply. Recently, the OA was around here early at 8:30 am, no idea if they checked.

Watering can and own water cannot be checked. Neighbors will probably need to report it. How evaporation-friendly a garden is designed cannot be checked.

No matter what ban/order comes, it will be difficult to verify. At most, it is possible through water meters.

The OP should answer the questions from for themselves.