Each student can calculate his or her water use and how it relates to rainfall and land area. The average water consumption is between 55 and 75 gallons per person per day, or 20,075 to 27,375 gallons per person per year. Of this 40% is used for the toilet, 30% is used in the bathroom sink and shower, 15% is used in the laundry, 10% is used in the kitchen and 5% is used outside. Looked at another way, 97% is used to transport wastes and 3% is used for drinking and cooking.
If we divide the water available by the daily usage we find that Lake Wintergreen could provide water to between 10,666 and 14,545 people. The article “Metabolism of Cities” says that a modern city of one million people takes in 625,000 tons of water per day and gives off 500,000 tons of sewage water with 120 tons of suspended solids in it. Water weighs 62 pounds per cubic foot. Six hundred twenty-five thousand tons/day x 2000 lb./ton x 1 cu. ft./62 lb. x 7.48 gal./cu. ft. = 150,800,000 gal./day Ö 1,000,000 = 150 gal./person/day.
This points out the fact that collections of people use two to three times more water than is individually used. Of the 150 gallons per person per day, an average of 65 gallons per day are for household use, 15 gallons per day are lost in leaks and an equal amount is used for street cleaning and fire fighting. The remainder, 55 gallons per day, is used by commerce and industry. One hundred fifty gallons/person/day x 365 days/year = 54,750 gallons per person per year in a modern city.
