Humans are extremely good at survival. That is the reason we are the most populous species on the planet. We have come up with innovative techniques to somehow thrive even in the harshest of environments. And we still come up with very nifty tricks to survive even when nature shows its full wrath. With a good presence of mind and wits around you, you can use these tricks to survive a natural calamity too. Strap a torch to a 10 liter can of water for ambient light You can easily light up a room with this contraption when the power lines go out during a disaster.

Add a few drops of household bleach to water to make it drinkable again

Bleach is a good disinfectant, and when you do not have heat to boil water, just use a drop or two of bleach in a bottle full of water, and let it rest for a few minutes.

Use a piece of cloth to siphon water from a dirty source to a clean source

The cloth will filter most of the dirt from the dirty water.

You still have to boil that water, though.