That's 1 inch of water per week. Most people don't live in a desert, so some of that 1 inch of water comes from rain. That is, assume each watering uses 1 inch

That's 1 inch of water per week. Most people don't live in a desert, so some of that 1 inch of water comes from rain. That is, assume each watering uses 1 inch and the watering is one per week, then: 6772 gal / week * 52 weeks = 352,000 gallons per year. The average American family uses about 300 gallons of water per day at home, says https://19january2017snapshot.epa.gov/www3/watersense/our_water/water_use_today.html https://19january2017snapshot.epa.gov/www3/watersense/our_wa... 300 gal/day * 365.25 days / year = 110,000 gallon per year which means the average family isn't putting 1" of water on their 10K sq ft lawn per week. Furthermore, the same source says "Nationally, outdoor water use accounts for 30 percent of household use", so that should be more like 33,000 gal / year on outdoor use. It therefore seems like your estimate is off by quite a bit. As an example adjustment for rain. Boston gets 3-4 inches of rain per month, so that's about 0.5 inches of extra watering needed per month, or 0.125 inches per week, or 1/8th of your estimate.