Is it possible to set a 'baseline usage' indicator for water meters on PnPSCADA? For consumption monitoring purposes it would be useful to be able to set a typical 'norm' for a group of meters, and then be able to flag, or get a report, of any meters which are above this for a particular period.

Yes.
Configure the consumption rate limit in Advanced Meter Settings.
It will cause an event when this limit is reached or exceeded.

The Advanced Meter Settings can of course be edited in bulk for a group of meters via the Tools->Bulk Edit screen.