As it happens OD&D's wilderness exploration game is built squarely on top of Outdoor Survival; a board game specifically about dying of thirst/hunger in the wilderness. It seems to me that game's deprivation rules are appropriate to wilderness exploration in D&D too, so I've translated them for DD (see below). Throw in the fatigue rules from Chainmail, and we're there.
Thirst and starvation in Outdoor Survival results in loss of mobility. A player in top condition can move 6 hexes per day, but as his condition worsens his movement rate slows. A player can (generously) survive at most 6 days without water, and at most 22 days without food; combined stresses will kill the player sooner. To generalise; thirst is about three times as severe as is hunger in the Outdoor Survival game.
Fatigue occurs in Chainmail as a result of extended periods of movement and/or combat. In Chainmail it has the effect of reducing a figure's classification on the Mass Combat Tables by one troop grade. As far as foot types are concerned, this essentially means the figure attacks at -1 (on a d6), is attacked at +1 (on a d6), and has a morale penalty.
Deprivation Rules Translated for DD
In a Nutshell
- -1/3rd movement per day without water,
- -1/6th movement per two-days without food,
- Movement penalties are cumulative,
- Any movement penalty includes fatigue,
- Death occurs at 0 movement.
In More Detail
- A PC can function normally without water for one day
- +1 day if he is heroic or has >14 constitution
- -1 day if he has <7 constitution, or in hot weather
- A PC can function normally without food for a period of two days
- +1 day if he is heroic
- +1 day if he has >14 constitution
- -1 day if he has <7 constitution
Except for the above "grace period":
- Movement rate is reduced by 1/3rd for each day without water, and
- Movement rate is reduced by 1/6th for each period (as above) without food.
Death occurs at 0 movement.
Any PC with impaired movement due to deprivation is also fatigued.
Chainmail's fatigue effect is represented as a -2 penalty to hit, to AC, and to morale checks.
Chainmail (effectively) imposes a -1 on a d6 for fatigue which is nearer to -3 on a d20, but -2 penalties occur elsewhere in DD so it seems prudent to maintain this symmetry. Chainmail's morale effect is much more complicated to quantify, so a simplistic but practical translation is to apply the same -2 penalty (but this time on a 2d6, making it is a more significant penalty).
A normal man can move 12" on the first day without water. He will be fatigued and move only 8" on the second day (after one full day without water). He will likewise be fatigued but move only 4" on the third day (after two full days without water), and will die on the fourth day (after three full days without water).