What if we lived off rainfall alone?

Just out of curiousity, how far off is our current water usage from the amount of rain that falls on us?

Our land is 1.32 acres, and the average rainfall here is 16 inches. This means that an average of 573,150 gallons of rain fall on the land each year. Our roof surfaces (house and garage and workshop) are a total of 2,927 square feet. This means that an average of 29,184 gallons of rain fall on our roofs each year.

Over the last year we have used approximately 54,000 gallons from the municipal water district. That’s equal to 4,500 gallons per month or 148 gallons per day. This is for two adults and one child, including all household water and yard water. Our vegetable garden is this size

Upper section

Lower section

and we have about 20 fruit trees plus berries and grapes. We water no lawn or ornamental plants.

So, 54,000 gallons from the municipal water district minus the 29,184 gallons that our roofs could have collected means a deficit of 24,816 gallons. Or, we’ve use about twice as much water in the past year as could have fallen on our roofs (and so could have been collected).

There are other factors that have to be mentioned. We have only received 10 of our average 16 inches of rain over the last year, and this increased how much we had to use from the water district. Also, our water use in the yard has decreased by around 50% since changing over all irrigation from sprinkler to drip starting about six months ago.

I’d guess that with a few additional improvements in our water use efficiency we could use only our roofs’ 29,184 gallons a year while noticing very little difference in our lifestyle and yield from the yard.

On the other hand, I don’t know what any of this means.

Who cares if you use only as much as your roof collects, since that says as much about how big your roof is as it does about your water use. But I just felt like there should be some crude correlation between how much rain my living quarters can harvest and the amount of water I should use. I’m not sure why. The more I think about it the less sensible it sounds.

It may just be that I have rain in the brain these days since everywhere there is talk of the drought, and then we’re getting unusual weekly rains in May with daily high temperatures only in the 60s, which is wetter and cooler than most of the winter!