The rule of 3 tells us just as we can only survive 3 hours without shelter in severe conditions, we can only expect to last a maximum of 3 days without water.
This particular pillar of survival is more obvious than the previous two but is a strong contender for the elusive “most important” title. Water isn’t only necessary for staying hydrated, but also for washing (especially important if any wounds are sustained) and cooking.
It might be tempting to stick to the minimum: 1 gallon per person per day. But this doesn’t take into account the fact you’re likely to have a higher activity level in a survival situation and heat exposure drastically reduces the amount of time you’re able to survive without water. Nor does it factor in the non-potable uses of water – cooking and washing, as mentioned above.
A good rule of thumb is to double your expected water requirements when preparing for a survival scenario. This means 2 gallons of water per person per day as a hard minimum.
Whether you choose to follow the recommended minimum of storing enough water to last everyone in your party for two weeks is ultimately up to you. However, it is recommended.
If you have the storage space (especially if you’re preparing more than one location in advance), try to aim for about 30 days’ water supply. That’s 60 gallons per person, which can take up a lot of space. If you follow the next piece of advice, you might be able to get away with less.
Make sure you have a safe, reliable means of getting more water in a survival situation. You won’t be able to simply open the tap – you might not have access to one and even if you do, the water might be contaminated.
Instead, focus on water filtration and purification methods. This can include, but should not be limited to, boiling water you collect from moving water sources (streams, rivers) and rainfall. Including water disinfection tablets in your survival kit can mean the difference between life and death.