Today I have been keeping track of my water usage, and also trying to economise on it as if it were precious. It came to about 1.3l for drinking, 0.7l for cooking and 1l for washing, or about 3 litres in total (about 3/4 of a US gallon).

Drinking includes 3 coffees, 2 glasses of juice and some milk with breakfast cereal. I had my usual sedentary life-style, as if confined to the house by quarantine.

Cooking was mostly spaghetti for lunch and rice for tea. Most of that water ended up in the food. About 200ml was lost to evaporation. There was also about 250ml of "grey water" left over which I've counted as waste, but which is quite drinkable (I used some for one of the coffees). Rice is easier to cook in low water than spaghetti.

Washing included my hands, face and teeth, and also plates, cutlery etc after cooking. I was aiming for a low but realistic level of hygiene, sustainable for a few weeks. I'm pretty good at getting plates clean with minimal water. Hand-washing is much harder. Paper towels helped.

I didn't include water used in flushing the loo. That would have seemed very wasteful of drinking water. In an emergency I'd hope to either use wild non-drinking water, or else make other arrangements.

I didn't include any clothes or hair washing. I figure that's realistic for a few weeks, but not really long-term. I didn't have any first-aid needs. My pets can find their own water.

I live alone. I suspect it could be hard to get other people to adopt the same level of water-discipline. 3 litres felt quite extreme; 4 litres per day might be a better rule of thumb for me. As it happens, I have about 50 litres stockpiled, which is about the limit of what is convenient for me. I also have about 5 rolls of paper towels stockpiled, and I think now I will increase that - it's easier to store because it's lighter and doesn't expire.