As much as I hate having to rush around looking for ice to water plants, I have to say a thirst bar/scale does seem like something obvious that ought to be there. Especially given that water units are bottles.
Several players have suggested having Thirst as a player stat. It would certainly be easy to add, but I don't know that it would necessarily make for a better game? Would people want one more progress bar / number to keep an eye on and be replenishing? It's something I could try out eventually.
As a side note, I'm probably going to be adding some sort of "water tap" as a base object so that players can take water back *out* of the Water Supply modules (and use for drinking / cooking etc).
@dikktor - what sort of info are you looking for about the RTGs?