Hydration - Water containers come in many sizes and styles so you need to choose the most appropriate for what you intend to undertake. Here's a quick Nomad run down:
*5 lt - 1.5lt standard water bottles - individual use
* 1 lt - 2 lt collapsible bladder bottles - individual use
* Water chambers - individual use for inserting into a predesigned compartment in your rucksack or daysack with a drinking straw
* 5 - 10 lt bladders - designed for camp use
* flasks - for individuals to keep drinks warm/cold
For individauls it is best to carry two litres of drinking water on you at all times. This can be in one large container or split between two smaller containers. For those on a high exertion expedition or trek, you will need to carry upto 10 litres for the day.