If waterways become polluted, or your environment turns arid, acquiring enough clean water for you or your group can be problematic and time consuming. The least time you need to spend on any one task, the better, because you will have a LOT of tasks.
I have recently become aware of some new water gathering techniques, one of which is described below.
These devices are rather simple, basically they consist of a net which collects moisture from the atmosphere. The water particles collect and drip down the nets where they are collected. Not only is the water clean, but the device will work unattended, leaving you free for the many other chores you will be tasked with.
Only basic periodic maintenance is needed.
As their name suggests, they work best when a thick fog rolls in, but there is almost always moisture present in the atmosphere as the earth rolls under her blanket of air. Even in an arid desert, moisture laden air will roll in overnight and should present you with at least a little water - providing you get to it before it evaporates.
This video, from non-profit organisation FogQuest will introduce you to this simple concept;
As you can see, they consist of a simple net with a trough below. It looks like they have fashioned this gutter out of PVC piping cut in half, very simple.
There will be plenty of "trash" and "debris" around after the apocalypse which can be put to good use for those with a little knowledge, and perhaps, a multitool. It's pretty hard to cut PVC piping with your teeth and fingernails.
One can imagine you could even improvise such a device in the wild using fronds or long leaves to collect the moisture, and sliced bamboo (if you are lucky enough to have some) as the guttering. Guttering could also be fashioned from large leaves or paper bark properly shaped. Of course, such a setup will require more maintenance and frequent rebuilding. So perhaps some netting in your kit would not go astray...
Some areas will be more suited to this device than others. Areas with high elevation can expect more fog than land closer to sea level. Terrain where clouds are forced to move up over mountains are especially suitable.
Setting the mesh up perpendicular to prevailing winds will yield the most water, and areas with a consistent wind direction is ideal.
As with everything survival related, it is best to experiment beforehand to see what works for you, rather than be fumbling around at the last minute.
This is by no means a 100% solution to everyone's water needs, it is but one more tool in your arsenal of knowledge.