So as I was reminded today, Create Water is something of a problem.
It is an example of why I call a story-breaking spell. A spell which, while it might not have any particularly mechanic-breaking power, completely circumvents some challenges - and also undermine the actual world-building, unless playing a tippy-verse style campaign. (Which I wouldn't, personally.)
In this specific case, I am running a mega-campaign in Osirion, framed around the Mummy's Mask adventure path, but mixing in AD&D's Deserts of Desolation (into the middle two books in that relavnt section0, and as many PF1 Osirion modules and society bits as I could cram in.
The PCs will reach the relevant part of Shifting Sands at a first-order magnitude pass estimated level of 8. (It might be higher.)
(I'm playing a hybrid of 3.5/PF1, though it is more PF1 than 3.5 at this point.)
According to the rules a Medium creature ina hot environment requires 1 gallon of water per day, two if the temperature spikes.
Create Water, a 0th level spell, can create 2 gallons/level.
In 3.5, this would mean a single spellcaster would only be able to cast it four times. (8 gallaons/level.) Pathfinder 1 has this unlimited, but I have already capped some captrips - Create Water among them, along with 3.5's Cure/Inflict Minor Wounds - to only be able to be cast four times (same number as you would in 3.5) before being expended.
However, that's still 64 gallons of water per day at level 8 (from a single 0th level spell slot) - eight cubic feet, so maybe a bathfull? That means a single 0th level spell slot can obiviate the need for the party to carry water, as that would be enough for eight party members AND THEIR CAMELS (at 4 gallons/day so a total of 40 gallons), but horror of horrors, they'd require a second 0th level spell slot for hot days (where they'd need 80 gallons).
This kind of defeats the point of, like, ever having any challenge in survival.
"But Aotrs, adventurers shouldn't ever have to worry about being attacked resting or food or water, that's something that they should be able to hand-wave away as never being important!" I disagree and I don't want them to do that. Especially in a campaign in which that's... Kind of a point.
So, I need to fix one of two things.
One, nerf Create Water; either by reducing the amount it creates, or perhaps more reasonably, limiting the amount of water it can create per cast (ala spell damage dice cap) - or even, perhaps, raising the level of the spell. To the point it should mitigate - but not obiviate - the amount of water the PCs will have to deal with.
Two, adjudicate whether the quoted 1-2 gallons of water per day is actually (close enough to being) right and to adjust if not.
I am entirely open to other suggestions on how to make this work; perhaps by making sure the PCs carry sufficient containers for that water, but that seems (by the time you add a camel) almost trivial to fix.
How did everyone else handle this in Mummy's Mask specifically?
One other factor in play in this specific case is a limitation of the character classes the PCs can choose - specifially, they are not allowed to have any of the classes that have seen regular use (which basically wipes out the entire core classes of both 3.5/PF1), which should mitigate stuff like Rope Trick/Magnificant Mansion et al shanigans.
(This time. I was EXTREMELY generous to the current campaign's party in allowing the wizard to have a special, upgraded version of Rope Trick that was 3rd level but did not asplode when the party took theie Handy Haversacks in it when I realised that was what would happen with the regular version that they had been using.)
Create Food and Water is another potential problem, but at least that's coming off a 3rd level spell slot and would require either and oracle burnig a spell learned or a shaman in the party, neither of which is guarenteed; and scrolls, of course, would cost more.
My first thought is: Mummy's Mask isn't about resource management; they'll be too powerful at that level for the heat to matter anyways.
But a more constructive answer that could actually help you is: I don't remember where in the Mummy's Mask board I saw it, but someone had the idea of water / cold-based spells having a caster level check and the spirits / elemental powers in the area get aggitated if someone casts too many water / cold-based spells so they'll track down the source of the disruption and try to stop it. (Read: elementals or some other type of creature shows up and attacks the party. Something with a blue dragon's "Desert Thirst" ability or a dust / sand-based creature would be thematically appropriate.)