Water is the elixir of life. In fact, water may be the place where life began.
There should be no doubt in anyone’s mind that we cannot live without it. You can live for weeks without food but only a few days without water. You don’t want to come to the bottom of a 900 foot climb to get out on the Mount of the Holy Cross Trail only to find that the water bladder is dry. That would make a very long, dry climb out. You need a source of extra water. Can you afford to trust that stream you just crossed?
Water is a tough “extra” to have in your pack. If you are following a stream along your trail, you can replenish your supply. If you are going to a desert environment or where water is unreliable, you may end up carrying a heavy pack just for the water. Each liter of water weighs 2.2 pounds. If you can get by on a bare minimum of 2 liters per day and plan to be out 3 days, you will need to find room for 6 liters of water weighing 13.2 pounds. If you need water to cook or rehydrate your meals, you will need more. Factor that along with the physical output and altitude and it can become a burden too heavy and bulky to carry. If that is still the desired adventure, start training with the heavy pack soon.
For those of us who choose a more accommodating environment in which to hike, the replenishment of water is easier and only requires that we assure that the water from a stream or lake is safe to drink. There are three levels of concern with water from the environment: debris, bacteria and viruses. A good t-shirt can be used to filter out the larger pieces of debris. Most all filters are capable enough to take care of bacteria and some form of chemical treatment will take care of the viruses. In a desperate emergency, drink the water. The doctors can cure your resulting ailments.