My "basement" is pretty small.
I ran across some
Ziploc storage boxes at WallyWorld. I can get about a dozen in my compartment if I work it right.
However I kept myself in check and only use four of them. They have a seal so they are relatively water tight and they stack together very well. I haven't seen any other sizes other than the 26.5 quart ones I purchased.
I have one for fresh/potable water stuff, one for sewer stuff, one for electrical, and the other is tools and other miscellaneous stuff. I put colored duct tape on the ends to make them easier to ID in a hurry.
Aaron