Man, this is some great info. Thanks for sharing your knowledge with us.
My wife and I have budgeted, Two 500ml bottles of sealed bottled water each per day for just drinking. One each in the morning time. Then, another each in the later end of the day.
The two 18 gallon water collection tub in the back yard stay pretty full after a good rain. One is covered for possible bathing water. The other will be reserve to feed the dogs and purify for us.
We stand set for a good three months before we would have to break into purifying water form outside and resorting to the high calorie survival meal rations. That would give us another month to set up a plan for moving elsewhere if the local does not recover.
If it is bad enough to where after four months we still have to be in basic survival mode, it is time to move on elsewhere.