I’ve been poking around for the last hour and not getting anywhere – here’s hoping someone with superior google-fu can help me.
People in the U.S. use a lot of water in the summer keeping their lawns green – I’m willing to accept that as a given. What I’m looking for is some kind of reliable indication of what “a lot of water” might mean. I’ve found claims that 50% of all water use in the summer goes to lawns; I’ve found claims that there’s a 50% increase in water use in the summer, attributable to lawn-watering. These two figures (proportions) aren’t the same thing, right? Of course, since I can’t track either of these figures (proportions) back to any kind of authoritative source, I can’t begin to sort out what’s what … any ideas for where to look?
If you want anecdotal data, here are some facts about my water use:
Location: southeast Michigan
Irrigated area: front- and side-yard, probably 8000 to 9000 ft².
Method: pop-up, multi-zone sprinkers on a timer. Note: no rain detector in use, but I’ll do manual bypass if it’s rainy.
December Water/Sewer Bill: $29 and change
August Water/Sewer Bill: $100 and change
I’d say it’s more than treble. Granted, I don’t have a deduct meter (a separate meter for exterior-use water), but sewage charges are proportional to water use, I think.
(Note: we’re in the Great Lakes and have plenty of cheap water, so we have no real necessity for conservation. Our biggest problem is distribution pressure, so sometimes we have voluntary odd-even watering for daytime waterers. Exterior-use water discounts the sewage treatment cost, which is the largest cost of water supplies).
Well, my google fu isn’t turning up anything, either. My guess would be that there ain’t no such statistic, because how would you know? You’d have to walk around a neighborhood, observe who was watering their lawns and how often and for how long (which would mean basically 24 hour surveillance during the observation period, because some people have their automatic sprinklers set to run during the night), then do the math to calculate how much water they used, and then find out what their water bill was, and calculate what percentage of it went towards their lawn.
And you’d have to do this for an entire neighborhood. I can’t find anybody who’s undertaken that kind of study. Which probably explains why all that’s out there are the WAGs that you already found.
And the consumer surveys like this one aren’t much use, either, because it only samples “people who felt like filling out and returning a survey”, not “people who water their lawns”.
You might contact your local water authority (or any water authority). They probably have to project seasonal water usage and certainly have detailed records on past usage, and might have a good estimate of how much usage increases during the summer; maybe they have statistically correlated that to rainfall, something like that.
No, those proportions aren’t the same. A 50% percent increase attributed to lawns means that 1/3 of the water goes to lawns.
Yeah, okay, thanks – I think it may be the case that we can’t find definitive figures because there are no definitive figures. I did find a few sites (often local govt. sites and/or water depts.) with what seemed to be more or less reliable numbers for particular locales – that may be the best I can do.
Don’t forget that “lawns” aren’t the only source of water use differences between summer & winter. People wash cars more in summer, but probably take longer hot showers in winter. etc., In many states water consumption for agriculture outweighs consumer & industrial consumption 3x or more.
Also notice that “summer” & “winter” mean very different things in San Diego, Seattle, Minneapolis, Bangor, Miami, & Houston. In at least one of those places people water lawns more in winter because the grass grows year round but summer is when it rains.
So I think you can probably get a single reasonable number for a few counties or maybe a state, but you cannot generalize that to the country by simple multiplication.
And I strongly suspect that the 50% number you’ve found, like 88.5% of all internet- or media-sourced statistics, are made up on the spot by the author.
