Hum... Rain barrels. Usually in Florida, we get too much rain at one time and not enough in the rest of the seasons. In maine, seems like rain barrels or cisterns are the way to go. Alot of farms have a farm pond too. I grew up on maine land that had 3 major springs rising to the surface. Two of them, we used for drinking water (was tested and certified).
To inspector and nestor..
Here in florida, I'll sometimes put a very small amount of bleach in the water to control mosquitos, but more commonly, to control mildew or mold. Another trick for mosquitos if using a barrel type holding tank, is to put just enough oil (like cooking oil... NOT motor oil, lol) over the top. Larvee cannot live, adults can't lay eggs. I'll also periodically empty a barrel and let sun-bleach for a week or so, until I need it again.
We collect water off of our roof, for irrigation purposes.
Instead of gutters, we tend to use rain chains. They're easier for us to remove than gutters, whenever we have a hurricane warning.