For our Dark Sun campaign, we decided that foraging and hunting gets you 1/4 as much water as it gets food, in terms of people.

I then played with dice options until I arrived at some that felt right to me and maintained the same average as 1/4 the average of hunting/foraging.

The result was that foraging gets you 1d4-2 gallons of water, and hunting gets you 2d4-4. Note that a result of 0 is entirely possible. (If I did the math right, a single person who is untrained in Survival, resourceful, good at managing his water, and a little bit lucky can just barely manage to scrounge out a living, which I feel is appropriate for the campaign.)

It’s also worth noting that it is possible to carry enough water for smaller groups for a relatively significant amount of time, if you load up a cart or wagon with almost entirely water. A gallon of water weighs 1.05 stone (barrel amortized, since you have a 1 stone barrel per 20 gallons of water) and lasts one person one day. Since ACKS has a constant rate of animals to haulage capacity (regardless of the vehicle it is hooked up to, a heavy horse can carry 80 stone at 60’ per turn; since haulage capacity does not double when halving speed, for purposes of maximum journey length when carrying your own water, you want to keep the fast speed).

If you have a single cart being pulled by a heavy horse, with a single driver, you consume 1 day of rations (0.2 stone) + 1 gallon of water (1.05 stone, driver) + 4 gallons of water (4.2 stone, horse - I’m basing the four gallons of water on a quick googling, I actually originally did this math with a kank that requires only 2 gallons of water per day) = 5.45 stone of provisions per day. With an 80 stone capacity that means you can load up with a maximum of 14.5 days of provisions (I rounded.)

What I find particularly interesting is that larger caravans don’t increase the maximum time available to you. You devote N% of carrying capacity to provisions, you always get Y days of travel. If you have 80 stone and devote 40 to provisions, you get the same range as if you have 800 and devote 400 to provisions. (Of course, the guy with 400 stone of non-provisions has a much more valuable caravan. I also note that guards will alter this, especially mounted guards who will ruin everything, which makes sense with the Crusades; you can carry enough water for a fair amount of people for a few days, but there’s no way you can carry enough water for horses who are not themselves carrying the water.)

I rambled on for a while, so sorry about that, but hopefully someone finds it interesting!