Unimaginably large numbers are, unfortunately, hard to conceptualize. FEMA has delivered 6,200,000 gallons of water to Puerto Rico in the month since Hurricane Maria hit the island. That sounds like a lot of water and probably makes for a good press release. Problem is there are 3.5 million residents. Who should drink half a gallon or so a day (3/4 of a gallon is the WHO recommendation for an adult, but there are kids there too, and I like lazy math). There have been 30 days since the hurricane stuck. Three and a half million people drinking half a gallon of water a day for thirty days is 52,500,000 gallons of water. Not quite 12% of the water needed and my estimate is significantly low.
Doesn’t sound quite so impressive if you say FEMA has delivered 10% of the water needed in Puerto Rico. It also makes breaking into superfund sites to access water more understandable. 100% chance of death if you don’t get water, even an 98% chance of death from poisoning is a better option.