Water is one of the single most important preps you'll ever need to consider in your long term survival plans. Without enough water, much of your food will be useless, particularly if you are relying on a great deal of MREs or other freeze-dried foods.
If you have a great deal of grain or flour stored, without enough water to make anything out of these materials, you may as well not be storing any food. To digest any of the food you cook, you'll need plenty of water to flush it through your system.
For those reasons, it's important to store or be able to obtain as much water as you can get your hands on for the long term.
But even more important than that is the necessity to have a backup plan. And a backup plan for your backup plan. And so on and so forth.
The video on the following page explains how to do this properly.