Okay, then I'm not sure why you are posting it - that example is a "good example" - and, yes, there are many "good examples" of that effect in the book, oddly enough - I don't think we need any examples to agree on that.
Hmmm... yes, you are correct, and so I apologize for this one. I thought you were implying that it could be cast on someone else and the water changed - which it cannot do. But you're right - the spell is cast, and the "duration" is not not the "duration" that the water stays changed, but the duration during which any and all new water is changed - which is completely against the RAW.
(This would be the equiv of casting a single MuAn spell w/ Sun duration that allowed the mage to change any animal they touched all day long - and we know that's not how it works.)
However, I had already addressed spells such as this...
This is, inarguably, a legacy spell - you'll find it in 1st ed, and it comes straight out of older 1st gen RPG's. Canon or no, it does not fit within the canon definitions of Duration, nor "Target" - the new water was not "sensed" at the time of casting.
The one I had been thinking of was Treading the Ashen Path, and there are others, but this is in the same category.
Sensing the "Target" is one of the harder requirements of Hermetic Magic to adjudicate. You for instance don't need to sense the contents of a Room or Structure to cast a spell the affects those contents. You just need to sense the "Target" which is the room itself. Inversly there seem to be cases where you don't have to sense the "Part" that a spell targets as long as you can see the whole. Twist of the Tongue (ArM pg 123) at least would be a logistically difficult spell to cast if you had to actually observe the tongue when casting the spell. And it's difficult to figure how one is sensing the water targeted by Parching Wind or Curse of the Desert (ArM5 pg 123)
As far as Duration goes I do not have a problem with Drop in Drop out effects like LotF and don't see why they shouldn't be considered on option for new spells. Once you understand how the Limit of Arcane Connection interacts with big "T" Targets it's easy to see how Drop In Drop Out effects don't automatically run up against any of the hard limits of hermetic magic.
So a Target:Room Duration:Moon spell that gives anyone brought into the room a recovery bonus as long as they are inside the room is perfectly ok. Or you could do a similar spell that gives everyone in the room when the spell is cast a bonus that last a moon even if they leave the room. In both cases the caster might be compleatly unaware of all the people affected by the spell. Since the only requirement is that the caster be able to sense the Room.
Further I think it's wrong to label any effect that doesn't easily fall into the hard guidelines as not RAW whether it's from a "Legacy Spell" or not. After all if it's in a published material it is by definition RAW. I think it's better to assume that RAW is naturally flexible. And that so called "Legacy Spells" are often examples of just how flexible the guidelines can be. And are partly there as example to guide players into thinking up there own interesting and colorful effects.
If a player comes up with a cool spell that works like Treading the Ashen Path and is not to overpowered then they should be allowed to create that spell. You can't say that's not how Hermetic Magic works because clearly in one case it does. If the spell is to powerful then -oh well- Rule One is part of RAW as well.