Quote from Pacatus

How much water do you estimate you need to stock for a month per person?

This is a good question – the problem is, there can't be a “One size fits all” answer. We all have different bodies, we live in different climates and locations, and we have different levels of (expected/projected) activity. It also depends on the way in which food is meant to be prepared:

I've chosen rations, which are small, lightweight and airtight, and will soak up liquids, when preparing them, and I know from experience this reduces my need for additional drinking considerably. Compared to, let's say, using pasta as a staple, that saves on water. I also won't need water to do away with what my body turns those rations into and overall, I know from experience that I can go with really quite little water for a long time – except during summertime exertions. That said, if water is so scares as to make things harder as they would be already, that misses the point.

It is also worth considering geography and location: Not every area has natural springs to begin with; some are contaminated. Only some cities, where it is geographically feasible, have karstic springs (springs, where water doesn't just freely flow out, but which provide enough pressure to feed the city's veins without pumping). If the water supply was stagnant for a while, it'll be disinfected during the first few days, which means the water will be chlorinated at first. IF the water supply was stagnant, the sewage system was so, too. Especially if it rains, whatever foul substance was still in the pipes will be washed to the river the wastewater treatment plant drains into. Depending on geography, this could even contaminate groundwater and loop back to the freshwater supply, albeit dilute, of course. (Real example: In 2019, on the fourth day of a seven day blackout, the inhabitants of Caracas, Venezuela started drinking from the Guaire River, the heavily contaminated sewage river flowing through the city.)

I wrote to my city's water provider (the actual staff, not the politicians), and they were kind enough to give me a short "true" or "false" on my analysis of what would happen to my city in that case. The result is that, quite miraculously, most of the city would continue to have running water, which is collected in a (geographically) much higher region, and drained such, that even if the sewage plants fail, there won't be any issue at all (in terms of thirsty humans; tons of dead fish and whatnot, of course). I had downloaded and read the supply maps before, so I could ask to-the-point questions, and they seemed to appreciate my interest; however, ymmv. I hope your supplier won't consider such information a state secret, either

There are filters you can screw onto taps, to get drinkable water from the initially funky tap water (you might also want to boil it, but that implies having lots of fuel). Filters are also important when using natural springs, and especially with creeks or rivers (because you can never knows what lies around in the riverbed just a mile upstream -- the water might look clean, but could be contaminated with bacteria or other baddies just the same). Besides filters, there are small chlorine pills which can disinfect the contents of a canister.

Now, with all of that said, you'll know to take my approach with a grain of salt and to adapt it to your situation: I keep around 30l of water at home, in 1,5l plastic bottles, bundles of six. If I have used this up and there's still no drinkable water, I expect the city has already become quite uninhabitable for a single woman (by then, there'd be general chaos all over, and the unprepared would be starved and thirsty, ergo primal…). That's why I also have a canister and chlorine pills, for when I can drive to the countryside before that (ideal). If roads are jammed or barricaded (whether by stranded cars, highwayman or authorities), I'd be walking. However, it's not really possible to carry much more than a mere day's worth of water, which brings us back to filters. That sounds complicated, and it sort of is. However, after air, water is the second most vital ingredient to human life. It is better to have water, than to have a fancy radio, the most high-tech backpack or the sharpest knife anyone has ever forged. We can easily carry our belongings in a 3rd rate backpack for weeks and weeks, if we have to — sore shoulders aren't fatal. Which is to say: It is worth remembering what really matters, and not get lost in high-gloss gear catalogues (which I'm definitely prone to myself).

I'm afraid this wasn't as clear cut as “X litres per person, and half that for kids!”, but I hope by sketching my thought process, you might have a useful blueprint to draw your own conclusions

Quote from Julia

We can easily carry our belongings in a 3rd rate backpack for weeks and weeks, if we have to — sore shoulders aren't fatal.

(Somehow I couldn't edit my post, so this is a bit of a PS:) I do realise this was an overly sweeping generalisation. I wrote that much more for rhetoric than for face value, so please consider it a dramatic introduction to the sentence following it.

During the very first moments of a blackout there might (or might not…) still be SMS (technically a repurposed control channel of the cellular towers) or even mobile data. Many towers have small buffer batteries; but they only last a couple of minutes, there'd be data congestion once everyone is suddenly using it, and eventually the backbone network will shutdown anyway. OK, so what's the point then? Here's my thought: I always know quite exactly where my cell phone is, anyway. So when the power would go out, the very first and indeed immediate thing I would do is text a friend who lives 200km (125mi) away, in another city but still in the same “grid district” (same high-voltage distribution network). She would do the same. If we get each other's text, we can be among the first to know with certainty it is a wide-spread (hence probably longer) thing. So while everyone else is getting cozy lighting candles, we'd get a move on, grab our gear, and leave the city perimeter. Under ideal conditions, we could clear the city by the time the first emergency radio broadcast is transmitted (potentially causing an initial flare of chaos). But we might both be sleeping. Or only one text might get through (in which case the other one would still benefit; still a win!). Or none might get through at all (in which case, at least we both saved five minutes worth of candle wax! ).

You might be able to adapt the underlying idea? Maybe there are (somewhat) younger friends who don't live too far away? Or maybe there are other folks, who would be similarly stranded? There is usually strength in numbers, and sometimes discussing things ahead of time can maximise the benefit