Just now, when I was running the kitchen tap at home, I reached over to close the refrigerator, then reached for the tap and turned it off. I took my time so this little endeavor took about 5 seconds.
After doing that, I started wondering how much water I'd wasted in that 5 seconds, while I left the tap running. So, I measured it. I ran the tap for exactly 5 seconds, into a 2 cup measuring cup and found that in 5 seconds I'd let 1 ¾ cups (450ml) of water go down the drain. Also please note, the tap was not completely open although it was a good flow.
I realized that 450ml of clean, potable water was probably more water than many people in third-world countries ever see in their whole lives. Yes, some of them have water but it is not clean or potable by our standards. Their water contains toxic minerals and microbes that cause deadly diseases and frequently they have to walk miles just to get that.
Then I realized that a 5-second, unnecessary outpouring was certainly not the only water I had wasted that day or any other. A wasteful second doesn't seem like a great oversight but check out these figures:5 seconds wasted tap water = .450 Liters (0.118 gallons)
Times 315 million people in the United States = 141,750,000 liters (37,446,388 gallons)
Times 365 days of any year = 51,738,750,000 liters (13,667,931,773 gallons) unintentionally and unnecessarily wasted in one year
Every person in the United States does at least some of the following every day: shower, bathe or partial body wash, wash dishes, brush teeth, wash a car or something else, water a lawn, trees or a garden. I think we can safely assume that each and every one of us wastes at least 5 seconds of water a day, 365 days a year. As you see above, at a minimum, that's 141.7 million liters (37.4 million gallons) of water wasted per day, just in the United States. That translates to 51.7 BILLION liters (13.6 BILLION gallons) of water a year.
Now, that is just the water allegedly wasted by average citizens through domestic use. Water for domestic use is arguably about 10% of our water consumption in the U.S., agricultural and industrial use making up the other 90%. Calculating the overall wasted water through all uses would generate numbers off the page.
I only want to bring your attention to the enormous multipliers involved in wasting a few seconds of water, or saving them. Each time you turn that tap off quickly or run it more slowly, you contribute to saving billions of gallons of water and indirectly, millions of lives, now and in the future.