My party is working through Castle Whiterock and we just got clobbered by a group of lions with Goodman Games desiccated template. This template allows for a D6 Con damage on every hit (no save) except if the creatures have immunity to dehydration. Are there items or spells that are available to a party with a 9th level cleric, paladin, and ranger that might provide just that? Pathfinder of D&D 3.X solutions are fine we're pulling material from both.
There look to be two spells of partial utility in Sandstorm:
Skin of the cactus only prevents non-lethal desiccation damage. Protection from Dehydration (Cleric 3, Druid 2, ranger 2, sor/wis 3, summer 3) does exactly what you want. First line states that it grants immunity to dehydration of any kind (given that that is what the attack does... that's a good start.) And it protects against both dehydration and dessication damage up to 100 points (10/level), without noting what kind of damage.
This is your best bet from traditional sources, and should be sufficiently effective without being overpowered to be allowed.