MUST be enforced. If warned of a crisis, fill as many receptacles as possible, especially in hot climates. Use dustbins, buckets, pots even strong polythene bags if they are only half filled and securely tied off. Store water in the dark. If light gets to it green algae will develop.
Water is bulky and heavy.
Do not store it in the attic or it may bring the ceiling down. Don't flush it. Outdoors you may have a swimming pool, water butts or a pond even water from a car radiator can be used. So water from these places is best kept for cleaning purposes. If it has to be used for drinking then boil it, collect the steam in clean cloth and wring them out.